Lasse Christiansen | Copenhagen University Hospital Hvidovre (original) (raw)

Papers by Lasse Christiansen

Scientific Reports

Motor skill acquisition depends on central nervous plasticity. However, behavioural determinants ... more Motor skill acquisition depends on central nervous plasticity. However, behavioural determinants leading to long lasting corticospinal plasticity and motor expertise remain unexplored. Here we investigate behavioural and electrophysiological effects of individually tailored progressive practice during long-term motor skill training. Two groups of participants practiced a visuomotor task requiring precise control of the right digiti minimi for 6 weeks. One group trained with constant task difficulty, while the other group trained with progressively increasing task difficulty, i.e. continuously adjusted to their individual skill level. Compared to constant practice, progressive practice resulted in a two-fold greater performance at an advanced task level and associated increases in corticospinal excitability. Differences were maintained 8 days later, whereas both groups demonstrated equal retention 14 months later. We demonstrate that progressive practice enhances motor skill learning...

Health and performance impairments provoked by thermal stress are societal challenges geographica... more Health and performance impairments provoked by thermal stress are societal challenges geographically spreading and intensifying with global warming. Yet, science may be underestimating the true impact, since no study has evaluated effects of sunlight exposure on human brain temperature and function. Accordingly, performance in cognitively dominated and combined motor-cognitive tasks and markers of rising brainstem temperature were evaluated during exposure to simulated sunlight (equal to ~1000 watt/m 2). Acute exposure did not affect any performance measures, whereas prolonged exposure of the head and neck provoked an elevation of the core temperature by 1 °C and significant impairments of cognitively dominated and motor task performances. importantly, impairments emerged at considerably lower hyperthermia levels compared to previous experiments and to the trials in the presents study without radiant heating of the head. These findings highlight the importance of including the effect of sunlight radiative heating of the head and neck in future scientific evaluations of environmental heat stress impacts and specific protection of the head to minimize detrimental effects. Approximately half of the global population live in regions where environmental heat stress is an issue that annually affects the ability to live healthy and productive lives 1,2. Negative effects range from thermal discomfort and impaired physical work capacity for healthy adults 3 to increased morbidity for workers regularly experiencing hyperthermia 1 and higher mortality for vulnerable citizens during heatwaves 4,5. While these issues are well-documented and exposure likely to be worsened by global warming, the effect of environmental heat stress on performance in cognitively dominated tasks is less clear. Intriguingly, in laboratory experiments, impairments in cognitively dominated task performance emerge only with profound hyperthermia 6-10 , whereas productivity losses in occupational settings are reported at considerably lower temperatures 1,11. The ability to maintain concentration and avoid attenuation of motor-cognitive performance is certainly of relevance for work and traffic safety as well as for minimizing the risks of making mistakes during other daily tasks. However, the lack of ecological test validity 1,12-14 as well as the low sensitivity of the stereotypical test protocols used in previous clinical or mechanistic studies in controlled indoor settings may have underestimated the impact of environmental heat stress in real-life scenarios 6-10. In particular, although laboratory-controlled environmental heat-stress studies commonly investigate or control for temperature, humidity and wind speed, solar radiation is often neglected, despite contributing a substantial heat load in outdoor settings, especially in the upright position with the human head directly exposed to solar radiation 15. Human brain function is highly dependent on a stable supply of blood glucose and oxygen, but the brain is also highly vulnerable to alterations in the ability to maintain cerebral heat balance 16,17. This vulnerability stems from the brain's increased metabolic heat production, being highly insulated due to its enclosure within the cranium , and relying primarily on heat removal via the cerebral perfusion for heat loss, thereby causing average brain temperature to be highly dependent on arterial blood temperature 16. During resting conditions, cerebral thermal homeostasis is maintained by removing ~1 kJ/min (the cerebral metabolic heat production) via the cerebral blood flow as the ~700 ml/min of blood entering the brain via the four feeding arteries leaves the brain with a 0.3 °C higher temperature 17. Consequently, cerebral heat loss is compromised in hyperthermic humans, as blood flow to the brain decreases while the temperature of incoming blood simultaneously increases 16. Indeed, the body

Acute cardiovascular exercise can promote motor memory consolidation following motor practice, an... more Acute cardiovascular exercise can promote motor memory consolidation following motor practice, and thus long-term retention, but the underlying mechanisms remain sparsely elucidated. Here we test the hypothesis that the positive behavioral effects of acute exercise involve the primary motor cortex and the corticospinal pathway by interfering with motor memory consolidation using non-invasive, low frequency, repetitive transcranial magnetic stimulation (rTMS). Forty-eight able-bodied, young adult male participants (mean age = 24.8 y/o) practiced a visuomotor accuracy task demanding precise and fast pinch force control. Following motor practice, participants either rested or exercised (20 min total: 3 Â 3 min at 90% VO 2peak) before receiving either sham rTMS or supra-threshold rTMS (115% RMT, 1 Hz) targeting the hand area of the contralateral primary motor cortex for 20 min. Retention was evaluated 24 h following motor practice, and motor memory consolidation was operational-ized as overnight changes in motor performance. Low-frequency rTMS resulted in off-line decrements in motor performance compared to sham rTMS, but these were counteracted by a preceding bout of intense exercise. These findings demonstrate that a single session of exercise promotes early motor memory stabilization and protects the primary motor cortex and the corticospinal system against interference. Ó 2020 IBRO. Published by Elsevier Ltd. All rights reserved.

Background: Within the context of the COVID-19 pandemic, the WHO endorses facemask use to limit a... more Background: Within the context of the COVID-19 pandemic, the WHO endorses facemask use to limit aerosol-spreading of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, concerns have been raised regarding facemask-associated dyspnea, thermal distress and self-reported impairment of cognition. Accordingly, we tested how facemask-use affects motor-cognitive performances of relevance for occupational safety. We hypothesized that mask use would affect cognitively dominated performances and thermal discomfort, but not alter whole-body thermal balance. Methods: Eight participants completed a facemask and a barefaced (control) trial, in a counterbalanced order, in 40°C and 20% humidity conditions. Motor-cognitive performance, physiological (rectal, mean skin and local facial temperatures) and perceptual (thermal comfort and dyspnea) measures were assessed at baseline and following 45 min of light work (100 W). Results: Perceived dyspnea was aggravated with prolonged facemask use (p = 0.04), resulting in 36% greater breathlessness compared to control. However, no other differences were observed in motor-cognitive performance, physiological strain, or thermal discomfort. Conclusions: Contradicting negative self-reported impacts of facemask-use, only dyspnea was aggravated in the present study, thereby reinforcing global recommendations of mask use, even in hot environments.

Background: The COVID-19 pandemic has broadly disrupted biomedical treatment and research includi... more Background: The COVID-19 pandemic has broadly disrupted biomedical treatment and research including non-invasive brain stimulation (NIBS). Moreover, the rapid onset of societal disruption and evolving regulatory restrictions may not have allowed for systematic planning of how clinical and research work may continue throughout the pandemic or be restarted as restrictions are abated. The urgency to provide and develop NIBS as an intervention for diverse neurological and mental health indications, and as a catalyst of fundamental brain research, is not dampened by the parallel efforts to address the most life-threatening aspects of COVID-19; rather in many cases the need for NIBS is heightened including the potential to mitigate mental health consequences related to COVID-19. Objective: To facilitate the re-establishment of access to NIBS clinical services and research operations during the current COVID-19 pandemic and possible future outbreaks, we develop and discuss a framework for balancing the importance of NIBS operations with safety considerations, while addressing the needs of all stakeholders. We focus on Transcranial Magnetic Stimulation (TMS) and low intensity transcranial Electrical Stimulation (tES) -including transcranial Direct Current Stimulation (tDCS) and transcranial Alternating Current Stimulation (tACS). Methods: The present consensus paper provides guidelines and good practices for managing and reopening NIBS clinics and laboratories through the immediate and ongoing stages of COVID-19. The document reflects the analysis of experts with domain-relevant expertise spanning NIBS technology, clinical services, and basic and clinical research e with an international perspective. We outline regulatory aspects, human resources, NIBS optimization, as well as accommodations for specific demographics. Results: A model based on three phases (early COVID-19 impact, current practices, and future preparation) with an 11-step checklist (spanning removing or streamlining in-person protocols, incorporating telemedicine, and addressing COVID-19-associated adverse events) is proposed. Recommendations on implementing social distancing and sterilization of NIBS related equipment, specific considerations of COVID-19 positive populations including mental health comorbidities, as well as considerations regarding regulatory and human resource in the era of COVID-19 are outlined. We discuss COVID-19 considerations specifically for clinical (sub-)populations including pediatric, stroke, addiction, and the elderly. Numerous case-examples across the world are described. Conclusion: There is an evident, and in cases urgent, need to maintain NIBS operations through the COVID-19 pandemic, including anticipating future pandemic waves and addressing effects of COVID-19 on brain and mind. The proposed robust and structured strategy aims to address the current and anticipated future challenges while maintaining scientific rigor and managing risk.

Paired corticospinal-motoneuronal stimulation (PCMS) elicits spinal synaptic plasticity in humans... more Paired corticospinal-motoneuronal stimulation (PCMS) elicits spinal synaptic plasticity in humans with chronic incomplete cervical spinal cord injury (SCI). Here, we examined whether PCMS-induced plasticity could be potentiated by acute intermittent hypoxia (AIH), a treatment also known to induce spinal synaptic plasticity in humans with chronic incomplete cervical SCI. During PCMS, we used 180 pairs of stimuli where corticospinal volleys evoked by transcranial magnetic stimulation over the hand representation of the primary motor cortex were timed to arrive at corticospinal-motoneuronal synapses of the first dorsal interosseous (FDI) muscle ~1-2 ms before the arrival of antidromic potentials elicited in motoneurons by electrical stimulation of the ulnar nerve. During AIH, participants were exposed to brief alternating episodes of hypoxic inspired gas (1 min episodes of 9% O 2) and room air (1 min episodes of 20.9% O 2). We examined corticospinal function by measuring motor evoked potentials (MEPs) elicited by cortical and subcortical stimulation of corticospinal axons and voluntary motor output in the FDI muscle before and after 30 min of PCMS combined with AIH (PCMS+AIH) or sham AIH (PCMS+sham-AIH). The amplitude of MEPs evoked by magnetic and electrical stimulation increased after both protocols, but most after PCMS+AIH, consistent with the hypothesis that their combined effects arise from spinal plasticity. Both protocols increased electromyographic activity in the FDI muscle to a similar extent. Thus, PCMS effects on spinal synapses of hand motoneurons can be potentiated by AIH. The possibility of different thresholds for physiological vs behavioral gains needs to be considered during combinatorial treatments.

When aerobic exercise is performed following skilled motor practice, it can enhance motor memory ... more When aerobic exercise is performed following skilled motor practice, it can enhance motor memory consolidation. Previous studies have suggested that dopamine may play a role in motor memory consolidation, but whether it is involved in the exercise effects on consolidation is unknown. Hence, we aimed to investigate the influence of dopaminergic pathways on the exercise-induced modulation of motor memory consolidation. We compared the effect of acute exercise on motor memory consolidation between the genotypes that are known to affect dopaminergic transmission and learning. By combining cluster analyses and fitting linear models with and without included polymorphisms, we provide preliminary evidence that exercise benefits the carriers of alleles that are associated with low synaptic dopamine content. In line with previous reports, our findings implicate dopamine as a modulator of the exercise-induced effects on motor memory consolidation, and suggest exercise as a potential clinical tool to counteract low endogenous dopamine bioavailability. Further experiments are needed to establish causal relations.

Attention Deficit Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder with a complex s... more Attention Deficit Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder with a complex symptomatology, and core symptoms as well as functional impairment often persist into adulthood. Recent investigations estimate the worldwide prevalence of ADHD in children and adolescents to be~7%, which is a substantial increase compared to a decade ago. Conventional treatment most often includes pharmacotherapy with central nervous stimulants, but the number of non-responders and adverse effects call for treatment alternatives. Exercise has been suggested as a safe and low-cost adjunctive therapy for ADHD and is reported to be accompanied by positive effects on several aspects of cognitive functions in the general child population. Here we review existing evidence that exercise affects cognitive functions in children with and without ADHD and present likely neurophysiological mechanisms of action. We find well-described associations between physical activity and ADHD, as well as causal evidence in the form of small to moderate beneficial effects following acute aerobic exercise on executive functions in children with ADHD. Despite large heterogeneity, meta-analyses find small positive effects of exercise in population-based control (PBC) children, and our extracted effect sizes from long-term interventions suggest consistent positive effects in children and adolescents with ADHD. Paucity of studies probing the effect of different exercise parameters impedes finite conclusions in this regard. Large-scale clinical trials with appropriately timed exercise are needed. In summary, the existing preliminary evidence suggests that exercise can improve cognitive performance intimately linked to ADHD presentations in children with and without an ADHD diagnosis. Based on the findings from both PBC and ADHD children, we cautiously provide recommendations for parameters of exercise. Preface ADHD is a neurodevelopmental disorder characterized by inattention and/or hyperactivity and impulsivity diagnosed in children before the age of 12 [1]. Worldwide prevalence of ADHD in children and adolescents is estimated to be between 5% and 10% [2-4] and recent surveys estimate that 57% of diagnosed cases persist into adulthood [5], with well-documented detrimental impact on social and academic skills [6]. The gravity of this diagnosis is underlined by the decreased life expectancy [7], comorbidity with other psychiatric diagnoses [8] and substance abuse [9], along with reduced quality of life for the affected children and their families [10]. Present treatment approaches most often

Acute intermittent hypoxia (AIH) enhances voluntary motor output in humans with central nervous s... more Acute intermittent hypoxia (AIH) enhances voluntary motor output in humans with central nervous system damage. The neural mechanisms contributing to these beneficial effects are unknown. We examined corticospinal function by evaluating motor evoked potentials (MEPs) elicited by cortical and subcortical stimulation of corticospinal axons and the activity in intracortical circuits in a finger muscle before and after 30 min of AIH or sham AIH. We found that the amplitude of cortically and subcortically elicited MEPs increased for 75 min after AIH but not sham AIH while intracortical activity remained unchanged. To examine further these subcortical effects, we assessed spike-timing dependent plasticity (STDP) targeting spinal synapses and the excitability of spinal motoneurons. Notably, AIH increased STDP outcomes while spinal motoneuron excitability remained unchanged. Our results provide the first evidence that AIH changes corticospinal function in humans, likely by altering corticospinal-motoneuronal synaptic transmission. AIH may represent a novel noninvasive approach for inducing spinal plasticity in humans.

To evaluate the prevalence of dehydration in occupational settings and contextualize findings to ... more To evaluate the prevalence of dehydration in occupational settings and contextualize findings to effects on performance in cognitively dominated tasks, simple and complex motor tasks during moderate and high heat stress.

Spinal cord injury (SCI) often results in impaired or absent sensorimotor function below the leve... more Spinal cord injury (SCI) often results in impaired or absent sensorimotor function below the level of the lesion. Recent electro-physiological studies in humans with chronic incomplete SCI demonstrate that voluntary motor output can be to some extent potentiated by noninvasive stimulation that targets the corticospinal tract. We discuss emerging approaches that use transcranial magnetic stimulation (TMS) over the primary motor cortex and electrical stimulation over a peripheral nerve as tools to induce plasticity in residual corticospinal projections. A single TMS pulse over the primary motor cortex has been paired with peripheral nerve electrical stimulation at precise interstimulus intervals to reinforce corticospinal synaptic transmission using principles of spike-timing dependent plasticity. Pairs of TMS pulses have also been used at interstimulus intervals that mimic the periodicity of descending indirect (I) waves volleys in the corticospinal tract. This data, along with information about the extent of the injury, provides a new framework for exploring the contribution of the corticospinal tract to recovery of function following SCI.

Background: A session of motor skill learning is accompanied by transient increases in corticospi... more Background: A session of motor skill learning is accompanied by transient increases in corticospinal excitability(CSE), which are thought to reflect acute changes in neuronal connectivity associated with improvements in sensorimotor performance. Factors influencing changes in excitability and motor skill with continued practice remain however to be elucidated. Objective/Hypothesis: Here we investigate the hypothesis that progressive motor practice during consecutive days can induce repeated transient increases in corticospinal excitability and promote motor skill learning. Methods: Changes in motor performance and CSE were assessed during 4 consecutive days of skill learning and 8 days after the last practice session. CSE was assessed as area under recruitment curves(RC) using transcranial magnetic stimulation(TMS). Two groups of participants(n ¼ 12) practiced a visuo-motor tracking-task with task difficulty progressively increased with individual proficiency(PPG) or with the same task level throughout all 4 days(NPPG). Results: Progressive practice resulted in superior motor learning compared to NPPG(p < 0.001). Whereas NPPG displayed increased CSE following only the first day of practice(p < 0.001), progressive motor practice was accompanied by increases in CSE on both the first and the final session of motor practice(p ¼ 0.006). Eight days after ended practice, the groups showed similar CSE, but PPG maintained superior performance at a skilled task level and transfer task performance(p < 0.005,p ¼ 0.029). Conclusion: The results demonstrate that progressive practice promotes both motor learning and repeated increases in CSE across multiple days. While changes in CSE did not relate to learning our results suggest that they signify successful training. Progressive practice is thus important for optimizing neurorehabilitation and motor practice protocols in general.

Sudden limb displacement evokes a complex sequence of compensatory muscle activity. Following the... more Sudden limb displacement evokes a complex sequence of compensatory muscle activity. Following the short-latency reflex and preceding voluntary reactions is an epoch termed the medium-latency reflex (MLR) that could reflect spinal processing of group II muscle afferents. One way to test this possibility is oral ingestion of tizanidine, an alpha-2 adrenergic agonist that inhibits the interneurons transmitting group II signals onto spinal motor neurons. We examined whether group II afferents contribute to MLR activity throughout the major muscles that span the elbow and shoulder. MLRs of ankle muscles were also tested during walking on the same day, in the same participants as well as during sitting in a different group of subjects. In contrast to previous reports, the ingestion of tizanidine had minimal impact on MLRs of arm or leg muscles during motor actions. A significant decrease in magnitude was observed for 2/16 contrasts in arm muscles and 0/4 contrasts in leg muscles. This discrepancy with previous studies could indicate that tizanidine's efficacy is altered by subtle changes in protocol or that group II afferents do not substantially contribute to MLRs.

It is well established that unilateral motor practice can lead to increased performance in the op... more It is well established that unilateral motor practice can lead to increased performance in the opposite non-trained hand. Here, we test the hypothesis that progressively increasing task difficulty during long-term skill training with the dominant right hand increase performance and corticomotor excitability of the left non-trained hand. Subjects practiced a visuomotor tracking task engaging right digit V for 6 weeks with either progressively increasing task difficulty (PT) or no progression (NPT). Corticospinal excitability (CSE) was evaluated from the resting motor threshold (rMT) and recruitment curve parameters following application of transcranial magnetic stimulation (TMS) to the ipsilateral primary motor cortex (iM1) hotspot of the left abductor digiti minimi muscle (ADM). PT led to significant improvements in left-hand motor performance immediately after 6 weeks of training (63 AE 18%, P < 0.001) and 8 days later (76 AE 14%, P < 0.001). In addition, PT led to better task performance compared to NPT (19 AE 15%, P = 0.024 and 27 AE 15%, P = 0.016). Following the initial training session, CSE increased across all subjects. After 6 weeks of training and 8 days later, only PT was accompanied by increased CSE demonstrated by a left and upwards shift in the recruitment curves, e.g. indicated by increased MEP max (P = 0.012). Eight days after training similar effects were observed, but 14 months later motor performance and CSE were similar between groups. We suggest that progressively adjusting demands for timing and accuracy to individual proficiency promotes motor skill learning and drives the iM1-CSE resulting in enhanced performance of the non-trained hand. The results underline the importance of increasing task difficulty progressively and individually in skill learning and rehabilitation training.

Human and animal studies have documented that neural circuitries in the spinal cord show adaptive... more Human and animal studies have documented that neural circuitries in the spinal cord show adaptive changes caused by altered supraspinal and/or afferent input to the spinal circuitry in relation to learning, immobilization, injury and neurorehabilitation. Reversible adaptations following, e.g. the acquisition or refinement of a motor skill rely heavily on the functional integration between supraspinal and sensory inputs to the spinal cord networks. Accordingly, what is frequently conceived as a change in the spinal circuitry may be a change in either descending or afferent input or in the relative integration of these, i.e. a change in the neuronal weighting. This is evident from findings documenting only task-specific functional changes after periods of altered inputs whereas resting responses remain unaffected. In fact, the proximity of the spinal circuitry to the outer world may demand a more rigid organization compared to the highly flexible cortical circuits. The understanding of all of this is important for the planning and execution of neurorehabilitation.

A single bout of high-intensity exercise can augment off-line gains in skills acquired during mot... more A single bout of high-intensity exercise can augment off-line gains in skills acquired during motor practice. It is currently unknown if the type of physical exercise influences the effect on motor skill consolidation. This study investigated the effect of three types of high-intensity exercise following visuomotor skill acquisition on the retention of motor memory in 40 young (25.3 AE 3.6 years), able-bodied male participants randomly assigned to one of four groups either performing strength training (STR), circuit training (CT), indoor hockey (HOC) or rest (CON). Retention tests of the motor skill were performed 1 (R1h) and 24 h (R1d) post acquisition. For all exercise groups, mean motor performance scores decreased at R1h compared to post acquisition (POST) level; STR (P = 0.018), CT (P = 0.02), HOC (P = 0.014) and performance scores decreased for CT compared to CON (P = 0.049). Mean performance scores increased from POST to R1d for all exercise groups; STR (P = 0.010), CT (P = 0.020), HOC (P = 0.007) while performance scores for CON decreased (P = 0.043). Changes in motor performance were thus greater for STR (P = 0.006), CT (P < 0.001) and HOC (P < 0.001) compared to CON from POST to R1d. The results demonstrate that high-intensity, acute exercise can lead to a decrease in motor performance assessed shortly after motor skill practice (R1h), but enhances offline effects promoting long-term retention (R1d). Given that different exercise modalities produced similar positive off-line effects on motor memory, we conclude that exerciseinduced effects beneficial to consolidation appear to depend primarily on the physiological stimulus rather than type of exercise and movements employed.

A single bout of high intensity aerobic exercise (~90% VO 2peak) was previously demonstrated to a... more A single bout of high intensity aerobic exercise (~90% VO 2peak) was previously demonstrated to amplify off-line gains in skill level during the consolidation phase of procedural memory. High intensity exercise is not always a viable option for many patient groups or in a rehabilitation setting where low to moderate intensities may be more suitable. The aim of this study was to investigate the role of intensity in mediating the effects of acute cardiovas-cular exercise on motor skill learning. We investigated the effects of different exercise intensities on the retention (performance score) of a visuomotor accuracy tracking task. Thirty six healthy male subjects were randomly assigned to one of three groups that performed either a single bout of aerobic exercise at 20 min post motor skill learning at 45% (EX45), 90% (EX90) maximal power output (W max) or rested (CON). Randomization was stratified to ensure that the groups were matched for relative peak oxygen consumption (ml O 2 /min/kg) and baseline score in the tracking task. Retention tests were carried out at 1 (R1) and 7 days (R7) post motor skill learning. At R1, changes in performance scores were greater for EX90 compared to CON (p<0.001) and EX45 (p = 0.011). The EX45 and EX90 groups demonstrated a greater change in performance score at R7 compared to the CON group (p = 0.003 and p<0.001, respectively). The change in performance score for EX90 at R7 was also greater than EX45 (p = 0.049). We suggest that exercise intensity plays an important role in modulating the effects that a single bout of cardiovascular exercise has on the consolidation phase following motor skill learning. There appears to be a dose-response relationship in favour of higher intensity exercise in order to augment off-line effects and strengthen procedural memory.

High intensity aerobic exercise amplifies offline gains in procedural memory acquired during moto... more High intensity aerobic exercise amplifies offline gains in procedural memory acquired during motor practice. This effect seems to be evident when exercise is placed immediately after acquisition, during the first stages of memory consolidation, but the importance of temporal proximity of the exercise bout used to stimulate improvements in procedural memory is unknown. The effects of three different temporal placements of high intensity exercise were investigated following visuomotor skill acquisition on the retention of motor memory in 48 young (24.0 ± 2.5 yrs), healthy male subjects randomly assigned to one of four groups either performing a high intensity (90% Maximal Power Output) exercise bout at 20 min (EX90), 1 h (EX90+1), 2 h (EX90+2) after acquisition or rested (CON). Retention tests were performed at 1 d (R1) and 7 d (R7). At R1 changes in performance scores after acquisition were greater for EX90 than CON (< 0.001) and EX90+2 (= 0.001). At R7 changes in performance scores for EX90, EX90+1, and EX90+2 were higher than CON (< 0.001, = 0.008, and = 0.008, resp.). Changes for EX90 at R7 were greater than EX90+2 (= 0.049). Exercise-induced improvements in procedural memory diminish as the temporal proximity of exercise from acquisition is increased. Timing of exercise following motor practice is important for motor memory consolidation.

The present study examined the activity profile, heart rate and metabolic response of small-sided... more The present study examined the activity profile, heart rate and metabolic response of small-sided football games for untrained males (UM, n 5 26) and females (UF, n 5 21) and investigated the influence of the number of players (UM: 1v1, 3v3, 7v7; UF: 2v2, 4v4 and 7v7). Moreover, heart rate response to small-sided games was studied for children aged 9 and 12 years (C91C12, n 5 75), as well as homeless (HM, n 5 15), middle-aged (MM, n 5 9) and elderly (EM, n 5 11) men. During 7v7, muscle glycogen decreased more for UM than UF (28 AE 6 vs 11 AE 5%; Po0.05) and lactate increased more (18.4 AE 3.6 vs 10.8 AE 2.1 mmol kg À 1 d.w.; Po0.05). For UM, glycogen decreased in all fiber types and blood lactate, glucose and plasma FFA was elevated (Po0.05). The mean heart rate (HR mean) and time 490% of HR max ranged from 147 AE 4 (EM) to 162 AE 2 (UM) b.p.m. and 10.8 AE 1.5 (UF) to 47.8 AE 5.8% (EM). Time 490% of HR max (UM: 16-17%; UF: 8-13%) and time spent with high speed running (4.1-5.1%) was similar for training with 2-14 players, but more high-intensity runs were performed with few players (UM 1v1: 140 AE 17; UM 7v7: 97 AE 5; Po0.05): Small-sided games were shown to elucidate high heart rates for all player groups, independently of age, sex, social background and number of players, and a high number of intense actions both for men and women. Thus, small-sided football games appear to have the potential to create physiological adaptations and improve performance with regular training for a variety of study groups.

We examined long-term musculoskeletal and cardiac adaptations elicited by recreational football (... more We examined long-term musculoskeletal and cardiac adaptations elicited by recreational football (FG, n 5 9) and running (RG, n 5 10) in untrained premenopausal women in comparison with a control group (CG, n 5 9). Training was performed for 16 months ($ 2 weekly 1-h sessions). For FG, right and left ventricular end-diastolic diameters were increased by 24% and 5% (Po0.05), respectively, after 16 months. Right ventricular systolic function measured by tricuspid annular plane systolic excursion (TAPSE) increased (Po0.05) in FG after 4 months and further (Po0.05) after 16 months (15% and 32%, respectively). In RG and CG, cardiac structure, E/ A and TAPSE remained unchanged. For FG, whole-body bone mineral density (BMD) was 2.3% and 1.3% higher Scand J Med Sci Sports 2010: 20 (Suppl. 1): 58-71

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