Arnold Haan - Academia.edu (original) (raw)

Papers by Arnold Haan

Research paper thumbnail of Effect of warm-up and precooling on pacing during a 15-km cycling time trial in the heat

International journal of sports physiology and performance, 2013

The best way to apply precooling for endurance exercise in the heat is still unclear. The authors... more The best way to apply precooling for endurance exercise in the heat is still unclear. The authors analyzed the effect of different preparation regimens on pacing during a 15-km cycling time trial in the heat. Ten male subjects completed four 15-km time trials (30°C), preceded by different preparation regimes: 10 min cycling (WARM-UP), 30 min scalp cooling of which 10 min was cycling (SC+WARM-UP), ice-slurry ingestion (ICE), and ice slurry ingestion + 30 min scalp cooling (SC+ICE). No differences were observed in finish time and mean power output, although power output was lower for WARM-UP than for SC+ICE during km 13-14 (17 ± 16 and 19 ± 14 W, respectively) and for ICE during km 13 (16 ± 16 W). Rectal temperature at the start of the time trial was lower for both ICE conditions (~36.7°C) than both WARMUP conditions (~37.1°C) and remained lower during the first part of the trial. Skin temperature and thermal sensation were lower at the start for SC+ICE. The preparation regimen provid...

Research paper thumbnail of Effect of stimulation intensity on assessment of voluntary activation

Muscle & nerve, 2012

The interpolated twitch technique is often used to assess voluntary activation (VA) of skeletal m... more The interpolated twitch technique is often used to assess voluntary activation (VA) of skeletal muscles. We investigated VA and the voluntary torque-superimposed torque relationship using either supramaximal nerve stimulation or better tolerated submaximal muscle stimulation, which is often used with patients. Thirteen healthy subjects performed maximal and submaximal isometric knee extensions with superimposed maximal or submaximal doublets (100 Hz). Superimposed torque relative to potentiated resting doublets was smaller with maximal nerve than with submaximal muscle stimulation. Maximal VA was 87 ± 7% and 93 ± 5% for submaximal muscle and maximal nerve stimulation, respectively. The individual voluntary torque-superimposed torque relationships were more linear for submaximal muscle stimulation, possibly leading to less overestimation of VA. Submaximal muscle stimulation can be used to estimate VA in the knee extensors. It is less painful, and overestimation of VA may be less comp...

Research paper thumbnail of Feasibility and validity of a graded one-legged cycle exercise test to determine peak aerobic capacity in older people with a lower-limb amputation

Physical therapy, 2012

Information concerning exercise tolerance and aerobic capacity is imperative for generating effec... more Information concerning exercise tolerance and aerobic capacity is imperative for generating effective and safe exercise programs. However, for older people with a lower-limb amputation, a standard exercise test is not available. The primary aim of the present study was to determine whether a graded 1-legged peak exercise test is feasible and provides a valid assessment of peak aerobic capacity in older people walking with a lower-limb prosthesis. This was a quasi-experimental case-control study. A total of 36 older people with a lower-limb prosthesis and 21 people who were able-bodied (controls) (overall mean age=61.7 years, SD=6.1) performed a discontinuous graded 1-legged exercise test. The peak respiratory exchange ratio was used as an indicator of maximal effort. The controls performed an additional 2-legged exercise test to provide insight into differences between the testing modes. All participants were able to perform the exercise test. Electrocardiographic tracings and blood...

Research paper thumbnail of Effects of alfacalcidol on the contractile properties of the gastrocnemius medialis muscle in adult and old rats

Journal of physiology and pharmacology : an official journal of the Polish Physiological Society, 2011

Vitamin D deficiency is associated with muscle weakness. It is unknown, however, how supra-physio... more Vitamin D deficiency is associated with muscle weakness. It is unknown, however, how supra-physiological levels of vitamin D affect skeletal muscle. To investigate the effects of increased serum vitamin D (1,25 (OH)₂D₃ or 1,25D) levels on the contractile properties of the medial gastrocnemius muscle, adult and old female Fischer₃₄₄ x Brown Norway F1 rats were orally treated with vehicle or the vitamin D analogue alfacalcidol for 1 or 6 weeks. Alfacalcidol treatment resulted in elevated 1,25D serum levels. This was accompanied by hypercalcaemia and a reduction in body mass, the latter largely attributable to a reduced food intake. However, kidney function, as reflected by normal creatinine serum levels, as well as heart mass were unaffected. The 17% reduction in maximal isometric force and power was explicable by a similar loss of muscle mass. The force-frequency relationship of the 6-week-treated old rats was shifted to the left, but neither the shape of the force-velocity relations...

Research paper thumbnail of Bone adaptation to altered loading after spinal cord injury: a study of bone and muscle strength

Journal of musculoskeletal & neuronal interactions

Bone loss from the paralysed limbs after spinal cord injury (SCI) is well documented. Under physi... more Bone loss from the paralysed limbs after spinal cord injury (SCI) is well documented. Under physiological conditions, bones are adapted to forces which mainly emerge from muscle pull. After spinal cord injury (SCI), muscles can no longer contract voluntarily and are merely activated during spasms. Based on the Ashworth scale, previous research has suggested that these spasms may mitigate bone losses. We therefore wished to assess muscle forces after SCI with a more direct measure and compare it to measures of bone strength. We hypothesized that the bones in SCI patients would be in relation to the loss of muscle forces. Six male patients with SCI 6.4 (SD 4.3) years earlier and 6 age-matched, able-bodied control subjects were investigated. Bone scans from the right knee were obtained by pQCT. The knee extensor muscles were electrically stimulated via the femoral nerve, isometric knee extension torque was measured and patellar tendon force was estimated. Tendon force upon electrical s...

Research paper thumbnail of Reproducibility of contractile properties of the human paralysed and non-paralysed quadriceps muscle

Clinical physiology (Oxford, England), 2001

This study assessed the reproducibility of electrically evoked, isometric quadriceps contractile ... more This study assessed the reproducibility of electrically evoked, isometric quadriceps contractile properties in eight people with spinal cord injury (SCI) and eight able-bodied (AB) individuals. Over all, the pooled coefficients of variation (CVps) in the SCI group were significantly lower (ranging from 0.03 to 0.15) than in the AB group (ranging from 0.08 to 0.21) (P<0.05). Furthermore, in all subjects, the variability of force production increased as stimulation frequency decreased (P<0.01). In subjects with SCI, variables of contractile speed are clearly less reproducible than tetanic tension or resistance to fatigue. Contractile properties of quadriceps muscles of SCI subjects were significantly different from that of AB subjects. Muscles of people with SCI were less fatigue resistant (P<0.05) and produced force-frequency relationships that were shifted to the left, compared with AB controls (P<.01). In addition, fusion of force responses resulting from 10 Hz stimulat...

Research paper thumbnail of Tendon Adaptive Response to Paralysis

Research paper thumbnail of Blunted hypertrophic response in old mouse muscle is associated with a lower satellite cell density and is not alleviated by resveratrol

Experimental Gerontology, 2015

Background: Sarcopenia contributes to the decreased quality of life in the older person. While re... more Background: Sarcopenia contributes to the decreased quality of life in the older person. While resistance exercise is an effective measure to increase muscle mass and strength, the hypertrophic response may be blunted in old age. Objectives: To determine 1) whether hypertrophy in the m. plantaris of old mice was blunted compared to adult and 2) whether this was related to a reduced satellite cell (SC) density and 3) how resveratrol affects hypertrophy in old mice. Methods: In adult (7.5 months, n = 11), old (23.5 months, n = 10) and old-resveratrol-treated (n = 10) male C57BL/6J mice, hypertrophy of the left m. plantaris was induced by denervation of its synergists. The contralateral leg served as control. Results: After six weeks, overload-induced myofiber hypertrophy and IIB-IIA shift in myofiber type composition were less pronounced in old than adult mice (P = 0.03), irrespective of resveratrol treatment. Muscles from old mice had a lower SC density than adult muscles (P = 0.002). Overload-induced SC proliferation (P b 0.05) resulted in an increased SC density in old, but not adult muscles (P = 0.02), while a decrease occurred after resveratrol supplementation (P = 0.044). Id2 and myogenin protein expression levels were higher in old than adult muscles (P b 0.05). Caspase-3 was expressed more in hypertrophied than control muscles and was reduced with resveratrol (P b 0.05). Conclusion: The blunted hypertrophic response in old mice was associated with a lower SC density, but there was no evidence for a lower capacity for proliferation. Resveratrol did not rescue the hypertrophic response and even reduced, rather than increased, the number of SCs in hypertrophied muscles.

Research paper thumbnail of CaMKII content affects contractile, but not mitochondrial, characteristics in regenerating skeletal muscle

BMC Physiology, 2014

Background: The multi-meric calcium/calmodulin-dependent protein kinase II (CaMKII) is the main C... more Background: The multi-meric calcium/calmodulin-dependent protein kinase II (CaMKII) is the main CaMK in skeletal muscle and its expression increases with endurance training. CaMK family members are implicated in contraction-induced regulation of calcium handling, fast myosin type IIA expression and mitochondrial biogenesis. The objective of this study was to investigate the role of an increased CaMKII content for the expression of the contractile and mitochondrial phenotype in vivo. Towards this end we attempted to co-express alpha-and beta-CaMKII isoforms in skeletal muscle and characterised the effect on the contractile and mitochondrial phenotype. Results: Fast-twitch muscle m. gastrocnemius (GM) and slow-twitch muscle m. soleus (SOL) of the right leg of 3-month old rats were transfected via electro-transfer of injected expression plasmids for native α/β CaMKII. Effects were identified from the comparison to control-transfected muscles of the contralateral leg and non-transfected muscles. α/β CaMKII content in muscle fibres was 4-5-fold increased 7 days after transfection. The transfection rate was more pronounced in SOL than GM muscle (i.e. 12.6 vs. 3.5%). The overexpressed α/β CaMKII was functional as shown through increased threonine 287 phosphorylation of β-CaMKII after isometric exercise and down-regulated transcripts COXI, COXIV, SDHB after high-intensity exercise in situ. α/β CaMKII overexpression under normal cage activity accelerated excitation-contraction coupling and relaxation in SOL muscle in association with increased SERCA2, ANXV and fast myosin type IIA/X content but did not affect mitochondrial protein content. These effects were observed on a background of regenerating muscle fibres.

Research paper thumbnail of Cytoarchitectural and metabolic adaptations in muscles with mitochondrial and cytosolic creatine kinase deficiencies

Bioenergetics of the Cell: Quantitative Aspects, 1998

Research paper thumbnail of Stimulus–response compatibility and affective computing: a review

Theoretical Issues in Ergonomics Science, 2007

Affective computing, a human-factors effort to investigate the merits of emotions while people ar... more Affective computing, a human-factors effort to investigate the merits of emotions while people are working with human-computer interfaces, is gaining momentum. Measures to quantify affect (or its influences) range from EEG, to measurements of autonomic nervous system responses (e.g., heart rate, blood pressure), to less objective self-reports. Here we claim that simple response-time measurements may be a viable alternative to measure (indirectly) the effects of affect on performance by providing a review of experimental paradigms and associated models of human information processing. In particular, we focus on stimulus-response compatibility paradigms that have provided important insights for human-factors research, for instance regarding the important role of the spatial layout of interface design on the efficiency of human task performance, to show that these paradigms can also be applied to investigate the role of affect in human-computer interaction.

Research paper thumbnail of Altered contractile properties of the quadriceps muscle in people with spinal cord injury following functional electrical stimulated cycle training

Spinal Cord, 2000

Objectives: To assess if contractile speed and fatigability of paralysed quadriceps muscles in in... more Objectives: To assess if contractile speed and fatigability of paralysed quadriceps muscles in individuals with spinal cord injury (SCI) can be altered by functional electrical stimulation leg cycle ergometry (FES-LCE) training. Settings: The Sint Maartenskliniek rehabilitation centre and the University of Nijmegen, Nijmegen, the Netherlands. Methods: Contractile properties of the quadriceps muscle were studied in seven people with motor-complete SCI who participated in a FES-LCE training program. Subjects trained for 30 min, three times per week for 6 weeks. Contractile speed and fatigue characteristics of electrically stimulated isometric contractions were compared before and after 6 weeks of FES-LCE. Results: Fatigue resistance improved following FES-LCE training as indicated by the higher forces maintained in response to repetitive electrical stimulation. In contrast with an improved fatigue resistance, the maximal rate of force rise was unaected, the speed of relaxation increased and the fusion of a 10 Hz force signal decreased. Furthermore, the force-frequency relationship shifted to the right at low stimulation frequencies, indicated by a decline in the ratio of 1 and 100 Hz force responses as well as the ratio of 10 and 100 Hz force responses. Conclusion: FES-LCE training can change the physiological properties of the quadriceps muscle in people with SCI. Even after a short period of training, the stimulated muscles become more resistant to fatigue. Furthermore, the increased speed of relaxation and associated decreased fusion and altered force-frequency relationship following training may be related to adaptations in the calcium handling processes, which re¯ect an early response of long-term disused muscles. Spinal Cord 38, 214 ± 223

Research paper thumbnail of Limitations of temperature measurement in the aural canal with an ear mould integrated sensor

Physiological Measurement, 2011

Aural canal temperature measurement using an ear mould integrated sensor (T ac ) might be a metho... more Aural canal temperature measurement using an ear mould integrated sensor (T ac ) might be a method suited for continuous non-invasive core temperature estimation in operational settings. We studied the effect of ambient temperature, wind and high intensity exercise on T ac and its ability to predict esophageal (T es ) and rectal temperatures (T re ). Seven subjects performed a protocol of rest at 21, 10 and 30 • C, followed by exercise and recovery at 30 • C. The subjects performed the protocol twice: with and without face-wind from halfway through the 30 • C rest period. Extra auricle insulation was applied at one side. Ambient temperature changes affected T ac significantly, while T es and T re remained stable. Insulating the auricle reduced but did not abolish this effect. Wind had an immediate cooling effect on T ac independent of auricle insulation. During exercise and recovery in 30 • C, T ac provided acceptable group predictions of T re in trials without wind (bias: −0.66 ± 0.21 • C covered, −1.20 ± 0.15 • C uncovered). Bias was considerably higher with wind, but variability was similar (−1.73 ± 0.11 • C covered, −2.49 ± 0.04 • C uncovered). Individual predictions of T es and T re showed more variation, especially with wind. We conclude that T ac may be used for core temperature assessment of groups in warm and stable conditions.

Research paper thumbnail of Non-invasive continuous core temperature measurement by zero heat flux

Physiological Measurement, 2011

Reliable continuous core temperature measurement is of major importance for monitoring patients. ... more Reliable continuous core temperature measurement is of major importance for monitoring patients. The zero heat flux method (ZHF) can potentially fulfil the requirements of non-invasiveness, reliability and short delay time that current measurement methods lack. The purpose of this study was to determine the performance of a new ZHF device on the forehead regarding these issues. Seven healthy subjects performed a protocol of 10 min rest, 30 min submaximal exercise (average temperature increase about 1.5 • C) and 10 min passive recovery in ambient conditions of 35 • C and 50% relative humidity. ZHF temperature (T zhf ) was compared to oesophageal (T es ) and rectal (T re ) temperature. T zhf -T es had an average bias ± standard deviation of 0.17 ± 0.19 • C in rest, −0.05 ± 0.18 • C during exercise and −0.01 ± 0.20 • C during recovery, the latter two being not significant. The 95% limits of agreement ranged from −0.40 to 0.40 • C and T zhf had hardly any delay compared to T es . T re showed a substantial delay and deviation from T es when core temperature changed rapidly. Results indicate that the studied ZHF sensor tracks T es very well in hot and stable ambient conditions and may be a promising alternative for reliable non-invasive continuous core temperature measurement in hospital.

Research paper thumbnail of Telemetry pill versus rectal and esophageal temperature during extreme rates of exercise-induced core temperature change

Physiological Measurement, 2012

Core temperature measurement with an ingestible telemetry pill has been scarcely investigated dur... more Core temperature measurement with an ingestible telemetry pill has been scarcely investigated during extreme rates of temperature change, induced by short high-intensity exercise in the heat. Therefore, nine participants performed a protocol of rest, (sub)maximal cycling and recovery at 30 °C. The pill temperature (T(pill)) was compared with the rectal temperature (T(re)) and esophageal temperature (T(es)). T(pill) corresponded well to T(re) during the entire trial, but deviated considerably from T(es) during the exercise and recovery periods. During maximal exercise, the average ΔT(pill)-T(re) and ΔT(pill)-T(es) were 0.13 ± 0.26 and -0.57 ± 0.53 °C, respectively. The response time from the start of exercise, the rate of change during exercise and the peak temperature were similar for T(pill) and T(re.) T(es) responded 5 min earlier, increased more than twice as fast and its peak value was 0.42 ± 0.46 °C higher than T(pill). In conclusion, also during considerable temperature changes at a very high rate, T(pill) is still a representative of T(re). The extent of the deviation in the pattern and peak values between T(pill) and T(es) (up to &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;1 °C) strengthens the assumption that T(pill) is unsuited to evaluate central blood temperature when body temperatures change rapidly.

Research paper thumbnail of Partial hexokinase II knockout results in acute ischemia–reperfusion damage in skeletal muscle of male, but not female, mice

Pflügers Archiv - European Journal of Physiology, 2010

Cellular studies have demonstrated a protective role of mitochondrial hexokinase against oxidativ... more Cellular studies have demonstrated a protective role of mitochondrial hexokinase against oxidative insults. It is unknown whether HK protective effects translate to the in vivo condition. In the present study, we hypothesize that HK affects acute ischemia-reperfusion injury in skeletal muscle of the intact animal. Male and female heterozygote knockout HKII (HK +/-), heterozygote overexpressed HKII (HK tg ), and their wild-type (WT) C57Bl/6 littermates mice were examined. In anesthetized animals, the left gastrocnemius medialis (GM) muscle was connected to a force transducer and continuously stimulated (1-Hz twitches) during 60 min ischemia and 90 min reperfusion. Cell survival (%LDH) was defined by the amount of cytosolic lactate dehydrogenase (LDH) activity still present in the reperfused GM relative to the contralateral (non-ischemic) GM. Mitochondrial HK activity was 72.6± 7.5, 15.7±1.7, and 8.8±0.9 mU/mg protein in male mice, and 72.7±3.7, 11.2±1.4, and 5.9±1.1 mU/mg in female mice for HK tg , WT, and HK +/-, respectively. Tetanic force recovery amounted to 33±7% for male and 17±4% for female mice and was similar for HK tg , WT, and HK +/-. However, cell survival was decreased (p=0.014) in male HK +/-(82±4% LDH) as compared with WT (98±5%LDH) and HK tg (97± 4%LDH). No effects of HKII on cell survival was observed in female mice (92±2% LDH). In conclusion, in this mild model of acute in vivo ischemia-reperfusion injury, a partial knockout of HKII was associated with increased cell death in male mice. The data suggest for the first time that HKII mediates skeletal muscle ischemia-reperfusion injury in the intact male animal.

Research paper thumbnail of Effect of antagonist muscle fatigue on knee extension torque

Pfl�gers Archiv European Journal of Physiology, 2003

The effect of hamstring fatigue on knee extension torque was examined at different knee angles fo... more The effect of hamstring fatigue on knee extension torque was examined at different knee angles for seven male subjects. Before and after a dynamic flexion fatigue protocol (180 s 1 , until dynamic torque had declined by 50%), maximal voluntary contraction extension torque was measured at four knee flexion angles (90, 70, 50 and 30). Maximal torque generating capacity and voluntary activation of the quadriceps muscle were determined using electrical stimulation. Average rectified EMG of the biceps femoris was determined. Mean dynamic flexion torque declined by 48€11%. Extensor maximal voluntary contraction torque, maximal torque generating capacity, voluntary activation and average rectified EMG at the four knee angles were unaffected by the hamstring fatigue protocol. Only at 50 knee angle was voluntary activation significantly lower (15.7%) after fatigue (P<0.05). In addition, average rectified EMG before fatigue was not significantly influenced by knee angle. It was concluded that a fatigued hamstring muscle did not increase the maximal voluntary contraction extension torque and knee angle did not change coactivation. Three possible mechanisms may explain the results: a potential difference in recruited fibre populations in antagonist activity compared with the fibres which were fatigued in the protocol, a smaller loss in isometric torque generating capacity of the hamstring muscle than was expected from the dynamic measurements and/or a reduction in voluntary activation.

Research paper thumbnail of Clinical and molecular overlap between myopathies and inherited connective tissue diseases

Neuromuscular Disorders, 2008

This review presents an overview of myopathies and inherited connective tissue disorders that are... more This review presents an overview of myopathies and inherited connective tissue disorders that are caused by defects in or deficiencies of molecules within the extracellular matrix (ECM). We will cover the myopathies caused by defects in transmembrane protein complexes (dystroglycan, sarcoglycan, and integrins), laminin, and collagens (collagens VI, XIII, and XV). Clinical characteristics of several of these myopathies imply skin and joint features. We subsequently describe the inherited connective tissue disorders that are characterized by mild to moderate muscle involvement in addition to the dermal, vascular, or articular symptoms. These disorders are caused by defects of matrixembedded ECM molecules that are also present within muscle (collagens I, III, V, IX, lysylhydroxylase, tenascin, fibrillin, fibulin, elastin, and perlecan). By focussing on the structure and function of these ECM molecules, we aim to point out the clinical and molecular overlap between the groups of disorders. We argue that clinicians and researchers dealing with myopathies and inherited connective tissue disorders should be aware of this overlap. Only a multi-disciplinary approach will allow full recognition of the wide variety of symptoms present in the spectrum of ECM defects, which has important implications for scientific research, diagnosis, and for the treatment of these disorders.

Research paper thumbnail of Influence of knee joint angle on muscle properties of paralyzed and nonparalyzed human knee extensors

Muscle & Nerve, 2005

Muscles of individuals with a spinal cord injury (SCI) exhibit an unexpected leftward shift in th... more Muscles of individuals with a spinal cord injury (SCI) exhibit an unexpected leftward shift in the force (torque)-frequency relationship. We investigated whether differences in torque-angle relationships between SCI and able-bodied control muscles could explain this shift. Electrically stimulated knee-extensor contractions were obtained at knee flexion angles of between 30°and 90°. Torque-frequency relationships were obtained at 30°, 90°, and optimum angle. Optimum angle was not different between groups but SCI-normalized torques were lower at the extreme angles. At all angles, SCI muscles produced higher relative torques at low stimulation frequencies. Thus, there was no evidence of a consistent change in the length of paralyzed SCI muscles, and the anomalous leftward shift in the torquefrequency relationship was not the result of testing the muscle at a relatively long length. The results provide valuable information about muscle changes occurring in various neurological disorders.

Research paper thumbnail of Knee extensor fatigability after bedrest for 8 weeks with and without countermeasure

Muscle & Nerve, 2007

We analyzed the effects of gravitational unloading on muscular fatigability and the effectiveness... more We analyzed the effects of gravitational unloading on muscular fatigability and the effectiveness of resistive vibration exercise to counteract these changes. Changes in knee extensor fatigability as a consequence of 8 weeks of horizontal bedrest with or without daily resistive vibration exercise were evaluated in 17 healthy male volunteers. Bedrest increased fatigability (% decrease in maximal voluntary isometric torque per minute exercise) from -7.2 +/- 0.5 to -10.2 +/- 1.0%/min (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05), which was accompanied by a decline (of 52.0 +/- 3.7%, P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) in muscle blood flow. Daily resistive vibration exercise training during bedrest prevented increases in fatigability (from -10.8 +/- 1.8 to -8.4 +/- 1.6%/min, P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05), and mitigated the reduction in blood flow (decline of 26.1 +/- 5.1%, P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). Daily resistive exercise may thus be suggested as an effective countermeasure during spaceflight and illness-related prolonged bedrest to combat the detrimental changes in muscle endurance that result from gravitational unloading.

Research paper thumbnail of Effect of warm-up and precooling on pacing during a 15-km cycling time trial in the heat

International journal of sports physiology and performance, 2013

The best way to apply precooling for endurance exercise in the heat is still unclear. The authors... more The best way to apply precooling for endurance exercise in the heat is still unclear. The authors analyzed the effect of different preparation regimens on pacing during a 15-km cycling time trial in the heat. Ten male subjects completed four 15-km time trials (30°C), preceded by different preparation regimes: 10 min cycling (WARM-UP), 30 min scalp cooling of which 10 min was cycling (SC+WARM-UP), ice-slurry ingestion (ICE), and ice slurry ingestion + 30 min scalp cooling (SC+ICE). No differences were observed in finish time and mean power output, although power output was lower for WARM-UP than for SC+ICE during km 13-14 (17 ± 16 and 19 ± 14 W, respectively) and for ICE during km 13 (16 ± 16 W). Rectal temperature at the start of the time trial was lower for both ICE conditions (~36.7°C) than both WARMUP conditions (~37.1°C) and remained lower during the first part of the trial. Skin temperature and thermal sensation were lower at the start for SC+ICE. The preparation regimen provid...

Research paper thumbnail of Effect of stimulation intensity on assessment of voluntary activation

Muscle & nerve, 2012

The interpolated twitch technique is often used to assess voluntary activation (VA) of skeletal m... more The interpolated twitch technique is often used to assess voluntary activation (VA) of skeletal muscles. We investigated VA and the voluntary torque-superimposed torque relationship using either supramaximal nerve stimulation or better tolerated submaximal muscle stimulation, which is often used with patients. Thirteen healthy subjects performed maximal and submaximal isometric knee extensions with superimposed maximal or submaximal doublets (100 Hz). Superimposed torque relative to potentiated resting doublets was smaller with maximal nerve than with submaximal muscle stimulation. Maximal VA was 87 ± 7% and 93 ± 5% for submaximal muscle and maximal nerve stimulation, respectively. The individual voluntary torque-superimposed torque relationships were more linear for submaximal muscle stimulation, possibly leading to less overestimation of VA. Submaximal muscle stimulation can be used to estimate VA in the knee extensors. It is less painful, and overestimation of VA may be less comp...

Research paper thumbnail of Feasibility and validity of a graded one-legged cycle exercise test to determine peak aerobic capacity in older people with a lower-limb amputation

Physical therapy, 2012

Information concerning exercise tolerance and aerobic capacity is imperative for generating effec... more Information concerning exercise tolerance and aerobic capacity is imperative for generating effective and safe exercise programs. However, for older people with a lower-limb amputation, a standard exercise test is not available. The primary aim of the present study was to determine whether a graded 1-legged peak exercise test is feasible and provides a valid assessment of peak aerobic capacity in older people walking with a lower-limb prosthesis. This was a quasi-experimental case-control study. A total of 36 older people with a lower-limb prosthesis and 21 people who were able-bodied (controls) (overall mean age=61.7 years, SD=6.1) performed a discontinuous graded 1-legged exercise test. The peak respiratory exchange ratio was used as an indicator of maximal effort. The controls performed an additional 2-legged exercise test to provide insight into differences between the testing modes. All participants were able to perform the exercise test. Electrocardiographic tracings and blood...

Research paper thumbnail of Effects of alfacalcidol on the contractile properties of the gastrocnemius medialis muscle in adult and old rats

Journal of physiology and pharmacology : an official journal of the Polish Physiological Society, 2011

Vitamin D deficiency is associated with muscle weakness. It is unknown, however, how supra-physio... more Vitamin D deficiency is associated with muscle weakness. It is unknown, however, how supra-physiological levels of vitamin D affect skeletal muscle. To investigate the effects of increased serum vitamin D (1,25 (OH)₂D₃ or 1,25D) levels on the contractile properties of the medial gastrocnemius muscle, adult and old female Fischer₃₄₄ x Brown Norway F1 rats were orally treated with vehicle or the vitamin D analogue alfacalcidol for 1 or 6 weeks. Alfacalcidol treatment resulted in elevated 1,25D serum levels. This was accompanied by hypercalcaemia and a reduction in body mass, the latter largely attributable to a reduced food intake. However, kidney function, as reflected by normal creatinine serum levels, as well as heart mass were unaffected. The 17% reduction in maximal isometric force and power was explicable by a similar loss of muscle mass. The force-frequency relationship of the 6-week-treated old rats was shifted to the left, but neither the shape of the force-velocity relations...

Research paper thumbnail of Bone adaptation to altered loading after spinal cord injury: a study of bone and muscle strength

Journal of musculoskeletal & neuronal interactions

Bone loss from the paralysed limbs after spinal cord injury (SCI) is well documented. Under physi... more Bone loss from the paralysed limbs after spinal cord injury (SCI) is well documented. Under physiological conditions, bones are adapted to forces which mainly emerge from muscle pull. After spinal cord injury (SCI), muscles can no longer contract voluntarily and are merely activated during spasms. Based on the Ashworth scale, previous research has suggested that these spasms may mitigate bone losses. We therefore wished to assess muscle forces after SCI with a more direct measure and compare it to measures of bone strength. We hypothesized that the bones in SCI patients would be in relation to the loss of muscle forces. Six male patients with SCI 6.4 (SD 4.3) years earlier and 6 age-matched, able-bodied control subjects were investigated. Bone scans from the right knee were obtained by pQCT. The knee extensor muscles were electrically stimulated via the femoral nerve, isometric knee extension torque was measured and patellar tendon force was estimated. Tendon force upon electrical s...

Research paper thumbnail of Reproducibility of contractile properties of the human paralysed and non-paralysed quadriceps muscle

Clinical physiology (Oxford, England), 2001

This study assessed the reproducibility of electrically evoked, isometric quadriceps contractile ... more This study assessed the reproducibility of electrically evoked, isometric quadriceps contractile properties in eight people with spinal cord injury (SCI) and eight able-bodied (AB) individuals. Over all, the pooled coefficients of variation (CVps) in the SCI group were significantly lower (ranging from 0.03 to 0.15) than in the AB group (ranging from 0.08 to 0.21) (P<0.05). Furthermore, in all subjects, the variability of force production increased as stimulation frequency decreased (P<0.01). In subjects with SCI, variables of contractile speed are clearly less reproducible than tetanic tension or resistance to fatigue. Contractile properties of quadriceps muscles of SCI subjects were significantly different from that of AB subjects. Muscles of people with SCI were less fatigue resistant (P<0.05) and produced force-frequency relationships that were shifted to the left, compared with AB controls (P<.01). In addition, fusion of force responses resulting from 10 Hz stimulat...

Research paper thumbnail of Tendon Adaptive Response to Paralysis

Research paper thumbnail of Blunted hypertrophic response in old mouse muscle is associated with a lower satellite cell density and is not alleviated by resveratrol

Experimental Gerontology, 2015

Background: Sarcopenia contributes to the decreased quality of life in the older person. While re... more Background: Sarcopenia contributes to the decreased quality of life in the older person. While resistance exercise is an effective measure to increase muscle mass and strength, the hypertrophic response may be blunted in old age. Objectives: To determine 1) whether hypertrophy in the m. plantaris of old mice was blunted compared to adult and 2) whether this was related to a reduced satellite cell (SC) density and 3) how resveratrol affects hypertrophy in old mice. Methods: In adult (7.5 months, n = 11), old (23.5 months, n = 10) and old-resveratrol-treated (n = 10) male C57BL/6J mice, hypertrophy of the left m. plantaris was induced by denervation of its synergists. The contralateral leg served as control. Results: After six weeks, overload-induced myofiber hypertrophy and IIB-IIA shift in myofiber type composition were less pronounced in old than adult mice (P = 0.03), irrespective of resveratrol treatment. Muscles from old mice had a lower SC density than adult muscles (P = 0.002). Overload-induced SC proliferation (P b 0.05) resulted in an increased SC density in old, but not adult muscles (P = 0.02), while a decrease occurred after resveratrol supplementation (P = 0.044). Id2 and myogenin protein expression levels were higher in old than adult muscles (P b 0.05). Caspase-3 was expressed more in hypertrophied than control muscles and was reduced with resveratrol (P b 0.05). Conclusion: The blunted hypertrophic response in old mice was associated with a lower SC density, but there was no evidence for a lower capacity for proliferation. Resveratrol did not rescue the hypertrophic response and even reduced, rather than increased, the number of SCs in hypertrophied muscles.

Research paper thumbnail of CaMKII content affects contractile, but not mitochondrial, characteristics in regenerating skeletal muscle

BMC Physiology, 2014

Background: The multi-meric calcium/calmodulin-dependent protein kinase II (CaMKII) is the main C... more Background: The multi-meric calcium/calmodulin-dependent protein kinase II (CaMKII) is the main CaMK in skeletal muscle and its expression increases with endurance training. CaMK family members are implicated in contraction-induced regulation of calcium handling, fast myosin type IIA expression and mitochondrial biogenesis. The objective of this study was to investigate the role of an increased CaMKII content for the expression of the contractile and mitochondrial phenotype in vivo. Towards this end we attempted to co-express alpha-and beta-CaMKII isoforms in skeletal muscle and characterised the effect on the contractile and mitochondrial phenotype. Results: Fast-twitch muscle m. gastrocnemius (GM) and slow-twitch muscle m. soleus (SOL) of the right leg of 3-month old rats were transfected via electro-transfer of injected expression plasmids for native α/β CaMKII. Effects were identified from the comparison to control-transfected muscles of the contralateral leg and non-transfected muscles. α/β CaMKII content in muscle fibres was 4-5-fold increased 7 days after transfection. The transfection rate was more pronounced in SOL than GM muscle (i.e. 12.6 vs. 3.5%). The overexpressed α/β CaMKII was functional as shown through increased threonine 287 phosphorylation of β-CaMKII after isometric exercise and down-regulated transcripts COXI, COXIV, SDHB after high-intensity exercise in situ. α/β CaMKII overexpression under normal cage activity accelerated excitation-contraction coupling and relaxation in SOL muscle in association with increased SERCA2, ANXV and fast myosin type IIA/X content but did not affect mitochondrial protein content. These effects were observed on a background of regenerating muscle fibres.

Research paper thumbnail of Cytoarchitectural and metabolic adaptations in muscles with mitochondrial and cytosolic creatine kinase deficiencies

Bioenergetics of the Cell: Quantitative Aspects, 1998

Research paper thumbnail of Stimulus–response compatibility and affective computing: a review

Theoretical Issues in Ergonomics Science, 2007

Affective computing, a human-factors effort to investigate the merits of emotions while people ar... more Affective computing, a human-factors effort to investigate the merits of emotions while people are working with human-computer interfaces, is gaining momentum. Measures to quantify affect (or its influences) range from EEG, to measurements of autonomic nervous system responses (e.g., heart rate, blood pressure), to less objective self-reports. Here we claim that simple response-time measurements may be a viable alternative to measure (indirectly) the effects of affect on performance by providing a review of experimental paradigms and associated models of human information processing. In particular, we focus on stimulus-response compatibility paradigms that have provided important insights for human-factors research, for instance regarding the important role of the spatial layout of interface design on the efficiency of human task performance, to show that these paradigms can also be applied to investigate the role of affect in human-computer interaction.

Research paper thumbnail of Altered contractile properties of the quadriceps muscle in people with spinal cord injury following functional electrical stimulated cycle training

Spinal Cord, 2000

Objectives: To assess if contractile speed and fatigability of paralysed quadriceps muscles in in... more Objectives: To assess if contractile speed and fatigability of paralysed quadriceps muscles in individuals with spinal cord injury (SCI) can be altered by functional electrical stimulation leg cycle ergometry (FES-LCE) training. Settings: The Sint Maartenskliniek rehabilitation centre and the University of Nijmegen, Nijmegen, the Netherlands. Methods: Contractile properties of the quadriceps muscle were studied in seven people with motor-complete SCI who participated in a FES-LCE training program. Subjects trained for 30 min, three times per week for 6 weeks. Contractile speed and fatigue characteristics of electrically stimulated isometric contractions were compared before and after 6 weeks of FES-LCE. Results: Fatigue resistance improved following FES-LCE training as indicated by the higher forces maintained in response to repetitive electrical stimulation. In contrast with an improved fatigue resistance, the maximal rate of force rise was unaected, the speed of relaxation increased and the fusion of a 10 Hz force signal decreased. Furthermore, the force-frequency relationship shifted to the right at low stimulation frequencies, indicated by a decline in the ratio of 1 and 100 Hz force responses as well as the ratio of 10 and 100 Hz force responses. Conclusion: FES-LCE training can change the physiological properties of the quadriceps muscle in people with SCI. Even after a short period of training, the stimulated muscles become more resistant to fatigue. Furthermore, the increased speed of relaxation and associated decreased fusion and altered force-frequency relationship following training may be related to adaptations in the calcium handling processes, which re¯ect an early response of long-term disused muscles. Spinal Cord 38, 214 ± 223

Research paper thumbnail of Limitations of temperature measurement in the aural canal with an ear mould integrated sensor

Physiological Measurement, 2011

Aural canal temperature measurement using an ear mould integrated sensor (T ac ) might be a metho... more Aural canal temperature measurement using an ear mould integrated sensor (T ac ) might be a method suited for continuous non-invasive core temperature estimation in operational settings. We studied the effect of ambient temperature, wind and high intensity exercise on T ac and its ability to predict esophageal (T es ) and rectal temperatures (T re ). Seven subjects performed a protocol of rest at 21, 10 and 30 • C, followed by exercise and recovery at 30 • C. The subjects performed the protocol twice: with and without face-wind from halfway through the 30 • C rest period. Extra auricle insulation was applied at one side. Ambient temperature changes affected T ac significantly, while T es and T re remained stable. Insulating the auricle reduced but did not abolish this effect. Wind had an immediate cooling effect on T ac independent of auricle insulation. During exercise and recovery in 30 • C, T ac provided acceptable group predictions of T re in trials without wind (bias: −0.66 ± 0.21 • C covered, −1.20 ± 0.15 • C uncovered). Bias was considerably higher with wind, but variability was similar (−1.73 ± 0.11 • C covered, −2.49 ± 0.04 • C uncovered). Individual predictions of T es and T re showed more variation, especially with wind. We conclude that T ac may be used for core temperature assessment of groups in warm and stable conditions.

Research paper thumbnail of Non-invasive continuous core temperature measurement by zero heat flux

Physiological Measurement, 2011

Reliable continuous core temperature measurement is of major importance for monitoring patients. ... more Reliable continuous core temperature measurement is of major importance for monitoring patients. The zero heat flux method (ZHF) can potentially fulfil the requirements of non-invasiveness, reliability and short delay time that current measurement methods lack. The purpose of this study was to determine the performance of a new ZHF device on the forehead regarding these issues. Seven healthy subjects performed a protocol of 10 min rest, 30 min submaximal exercise (average temperature increase about 1.5 • C) and 10 min passive recovery in ambient conditions of 35 • C and 50% relative humidity. ZHF temperature (T zhf ) was compared to oesophageal (T es ) and rectal (T re ) temperature. T zhf -T es had an average bias ± standard deviation of 0.17 ± 0.19 • C in rest, −0.05 ± 0.18 • C during exercise and −0.01 ± 0.20 • C during recovery, the latter two being not significant. The 95% limits of agreement ranged from −0.40 to 0.40 • C and T zhf had hardly any delay compared to T es . T re showed a substantial delay and deviation from T es when core temperature changed rapidly. Results indicate that the studied ZHF sensor tracks T es very well in hot and stable ambient conditions and may be a promising alternative for reliable non-invasive continuous core temperature measurement in hospital.

Research paper thumbnail of Telemetry pill versus rectal and esophageal temperature during extreme rates of exercise-induced core temperature change

Physiological Measurement, 2012

Core temperature measurement with an ingestible telemetry pill has been scarcely investigated dur... more Core temperature measurement with an ingestible telemetry pill has been scarcely investigated during extreme rates of temperature change, induced by short high-intensity exercise in the heat. Therefore, nine participants performed a protocol of rest, (sub)maximal cycling and recovery at 30 °C. The pill temperature (T(pill)) was compared with the rectal temperature (T(re)) and esophageal temperature (T(es)). T(pill) corresponded well to T(re) during the entire trial, but deviated considerably from T(es) during the exercise and recovery periods. During maximal exercise, the average ΔT(pill)-T(re) and ΔT(pill)-T(es) were 0.13 ± 0.26 and -0.57 ± 0.53 °C, respectively. The response time from the start of exercise, the rate of change during exercise and the peak temperature were similar for T(pill) and T(re.) T(es) responded 5 min earlier, increased more than twice as fast and its peak value was 0.42 ± 0.46 °C higher than T(pill). In conclusion, also during considerable temperature changes at a very high rate, T(pill) is still a representative of T(re). The extent of the deviation in the pattern and peak values between T(pill) and T(es) (up to &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;1 °C) strengthens the assumption that T(pill) is unsuited to evaluate central blood temperature when body temperatures change rapidly.

Research paper thumbnail of Partial hexokinase II knockout results in acute ischemia–reperfusion damage in skeletal muscle of male, but not female, mice

Pflügers Archiv - European Journal of Physiology, 2010

Cellular studies have demonstrated a protective role of mitochondrial hexokinase against oxidativ... more Cellular studies have demonstrated a protective role of mitochondrial hexokinase against oxidative insults. It is unknown whether HK protective effects translate to the in vivo condition. In the present study, we hypothesize that HK affects acute ischemia-reperfusion injury in skeletal muscle of the intact animal. Male and female heterozygote knockout HKII (HK +/-), heterozygote overexpressed HKII (HK tg ), and their wild-type (WT) C57Bl/6 littermates mice were examined. In anesthetized animals, the left gastrocnemius medialis (GM) muscle was connected to a force transducer and continuously stimulated (1-Hz twitches) during 60 min ischemia and 90 min reperfusion. Cell survival (%LDH) was defined by the amount of cytosolic lactate dehydrogenase (LDH) activity still present in the reperfused GM relative to the contralateral (non-ischemic) GM. Mitochondrial HK activity was 72.6± 7.5, 15.7±1.7, and 8.8±0.9 mU/mg protein in male mice, and 72.7±3.7, 11.2±1.4, and 5.9±1.1 mU/mg in female mice for HK tg , WT, and HK +/-, respectively. Tetanic force recovery amounted to 33±7% for male and 17±4% for female mice and was similar for HK tg , WT, and HK +/-. However, cell survival was decreased (p=0.014) in male HK +/-(82±4% LDH) as compared with WT (98±5%LDH) and HK tg (97± 4%LDH). No effects of HKII on cell survival was observed in female mice (92±2% LDH). In conclusion, in this mild model of acute in vivo ischemia-reperfusion injury, a partial knockout of HKII was associated with increased cell death in male mice. The data suggest for the first time that HKII mediates skeletal muscle ischemia-reperfusion injury in the intact male animal.

Research paper thumbnail of Effect of antagonist muscle fatigue on knee extension torque

Pfl�gers Archiv European Journal of Physiology, 2003

The effect of hamstring fatigue on knee extension torque was examined at different knee angles fo... more The effect of hamstring fatigue on knee extension torque was examined at different knee angles for seven male subjects. Before and after a dynamic flexion fatigue protocol (180 s 1 , until dynamic torque had declined by 50%), maximal voluntary contraction extension torque was measured at four knee flexion angles (90, 70, 50 and 30). Maximal torque generating capacity and voluntary activation of the quadriceps muscle were determined using electrical stimulation. Average rectified EMG of the biceps femoris was determined. Mean dynamic flexion torque declined by 48€11%. Extensor maximal voluntary contraction torque, maximal torque generating capacity, voluntary activation and average rectified EMG at the four knee angles were unaffected by the hamstring fatigue protocol. Only at 50 knee angle was voluntary activation significantly lower (15.7%) after fatigue (P<0.05). In addition, average rectified EMG before fatigue was not significantly influenced by knee angle. It was concluded that a fatigued hamstring muscle did not increase the maximal voluntary contraction extension torque and knee angle did not change coactivation. Three possible mechanisms may explain the results: a potential difference in recruited fibre populations in antagonist activity compared with the fibres which were fatigued in the protocol, a smaller loss in isometric torque generating capacity of the hamstring muscle than was expected from the dynamic measurements and/or a reduction in voluntary activation.

Research paper thumbnail of Clinical and molecular overlap between myopathies and inherited connective tissue diseases

Neuromuscular Disorders, 2008

This review presents an overview of myopathies and inherited connective tissue disorders that are... more This review presents an overview of myopathies and inherited connective tissue disorders that are caused by defects in or deficiencies of molecules within the extracellular matrix (ECM). We will cover the myopathies caused by defects in transmembrane protein complexes (dystroglycan, sarcoglycan, and integrins), laminin, and collagens (collagens VI, XIII, and XV). Clinical characteristics of several of these myopathies imply skin and joint features. We subsequently describe the inherited connective tissue disorders that are characterized by mild to moderate muscle involvement in addition to the dermal, vascular, or articular symptoms. These disorders are caused by defects of matrixembedded ECM molecules that are also present within muscle (collagens I, III, V, IX, lysylhydroxylase, tenascin, fibrillin, fibulin, elastin, and perlecan). By focussing on the structure and function of these ECM molecules, we aim to point out the clinical and molecular overlap between the groups of disorders. We argue that clinicians and researchers dealing with myopathies and inherited connective tissue disorders should be aware of this overlap. Only a multi-disciplinary approach will allow full recognition of the wide variety of symptoms present in the spectrum of ECM defects, which has important implications for scientific research, diagnosis, and for the treatment of these disorders.

Research paper thumbnail of Influence of knee joint angle on muscle properties of paralyzed and nonparalyzed human knee extensors

Muscle & Nerve, 2005

Muscles of individuals with a spinal cord injury (SCI) exhibit an unexpected leftward shift in th... more Muscles of individuals with a spinal cord injury (SCI) exhibit an unexpected leftward shift in the force (torque)-frequency relationship. We investigated whether differences in torque-angle relationships between SCI and able-bodied control muscles could explain this shift. Electrically stimulated knee-extensor contractions were obtained at knee flexion angles of between 30°and 90°. Torque-frequency relationships were obtained at 30°, 90°, and optimum angle. Optimum angle was not different between groups but SCI-normalized torques were lower at the extreme angles. At all angles, SCI muscles produced higher relative torques at low stimulation frequencies. Thus, there was no evidence of a consistent change in the length of paralyzed SCI muscles, and the anomalous leftward shift in the torquefrequency relationship was not the result of testing the muscle at a relatively long length. The results provide valuable information about muscle changes occurring in various neurological disorders.

Research paper thumbnail of Knee extensor fatigability after bedrest for 8 weeks with and without countermeasure

Muscle & Nerve, 2007

We analyzed the effects of gravitational unloading on muscular fatigability and the effectiveness... more We analyzed the effects of gravitational unloading on muscular fatigability and the effectiveness of resistive vibration exercise to counteract these changes. Changes in knee extensor fatigability as a consequence of 8 weeks of horizontal bedrest with or without daily resistive vibration exercise were evaluated in 17 healthy male volunteers. Bedrest increased fatigability (% decrease in maximal voluntary isometric torque per minute exercise) from -7.2 +/- 0.5 to -10.2 +/- 1.0%/min (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05), which was accompanied by a decline (of 52.0 +/- 3.7%, P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) in muscle blood flow. Daily resistive vibration exercise training during bedrest prevented increases in fatigability (from -10.8 +/- 1.8 to -8.4 +/- 1.6%/min, P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05), and mitigated the reduction in blood flow (decline of 26.1 +/- 5.1%, P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). Daily resistive exercise may thus be suggested as an effective countermeasure during spaceflight and illness-related prolonged bedrest to combat the detrimental changes in muscle endurance that result from gravitational unloading.