Joseph Weir | University of Kansas (original) (raw)

Papers by Joseph Weir

Research paper thumbnail of Recomendação de procedimentos da Sociedade Americana de Fisiologia do Exercício (ASEP) I: avaliação precisa da força e potência muscular; Procedures …

Rev. bras. ciênc. …, 2003

Base de dados : LILACS. Pesquisa : 524937 [Identificador único]. Referências encontradas : 1 [ref... more Base de dados : LILACS. Pesquisa : 524937 [Identificador único]. Referências encontradas : 1 [refinar]. Mostrando: 1 .. 1 no formato [Detalhado]. página 1 de 1, 1 / 1, LILACS, seleciona. para imprimir. Fotocópia. Texto completo. experimental, Documentos relacionados. Id: 524937 ...

Research paper thumbnail of Effects of Unilateral Concentric-Only Dynamic Constant External Resistance Training on Quadriceps Femoris Cross-Sectional Area

Journal of Strength and Conditioning Research, 1998

The purposes of this investigation were to examine the effects of unilateral concentric-only leg ... more The purposes of this investigation were to examine the effects of unilateral concentric-only leg extension dynamic constant external resistance (DCER) training on: (a) concentric DCER strength in the trained and contralateral (untrained) legs, (b) concentric isokinetic peak torque-velocity curves in the trained and contralateral legs, and (c) retention of concentric DCER strength and concentric isokinetic peak torque in the trained and contralateral legs following detraining. Sixteen adult male (mean age +/- SD = 24.0 +/- 4.0 yr) volunteers comprised training (TR, n = 8) and control (CTL, n = 8) groups. The TR group trained the nondominant limb with concentric-only leg extension DCER exercise (3-5 sets of 6 repetitions at 80% of one-repetition maximum load) for eight weeks followed by eight additional weeks of detraining. The CTL group did not train. All subjects were tested pretraining, posttraining and detraining for unilateral concentric-only leg extension DCER strength as well as concentric isokinetic peak torque at 1.05, 2.09, 3.14, 4.19, and 5.24 rad.s-1 in both legs. Mixed factorial ANOVAs, follow-up, and post-hoc analyses indicated that the training resulted in increased DCER strength in both the trained (42%) and contralateral (15%) legs as well as isokinetic peak torque in the trained leg (7-19%) at velocities ranging from 1.05 to 5.24 rad.s-1. There was no cross-training effect, however, for isokinetic peak torque. Furthermore, the training-induced increases in DCER strength and isokinetic peak torque were retained across eight weeks of detraining.

Research paper thumbnail of Isokinetic Dynamometry in Healthy Versus Sarcopenic and Malnourished Elderly: Beyond Simple Measurements of Muscle Strength

Journal of applied gerontology : the official journal of the Southern Gerontological Society, Jan 5, 2015

This study quantified systematic and intraindividual variability among three repetitions of conce... more This study quantified systematic and intraindividual variability among three repetitions of concentric isokinetic knee extension and flexion tests to determine velocity-related differences in peak torque (PT) and mean power (MP) in healthy elderly (HE) versus sarcopenic and malnourished elderly (SME). In total, 107 HE (n = 54 men, n = 53 women) and 261 SME (n = 101 men, n = 160 women) performed three maximal concentric isokinetic knee extension and flexion repetitions at 60°·s(-1) and 180°·s(-1). PT for Repetition 3 was lower than Repetitions 1 and 2, while MP for Repetition 1 was lower than Repetitions 2 and 3 in SME. Intraindividual variability among repetitions was correlated with strength, but not age, and was greater in SME, during knee flexion, and at 180°·s(-1). Velocity-related decreases in PT from 60°·s(-1) to 180°·s(-1) were more pronounced in SME. In summary, (a) the repetition with the highest PT value may be the best indicator of maximal strength, while the average may ...

Research paper thumbnail of Effects of the innervation zone on the time and frequency domain parameters of the surface electromyographic signal

Journal of Electromyography and Kinesiology, 2015

The purposes of the present study were to examine the effects of electrode placements over, proxi... more The purposes of the present study were to examine the effects of electrode placements over, proximal, and distal to the innervation zone (IZ) on electromyographic (EMG) amplitude (RMS) and frequency (MPF) responses during: (1) a maximal voluntary isometric contraction (MVIC), and; (2) a sustained, submaximal isometric muscle action. A linear array was used to record EMG signals from the vastus lateralis over the IZ, 30mm proximal, and 30mm distal to the IZ during an MVIC and a sustained isometric muscle action of the leg extensors at 50% MVIC. During the MVIC, lower EMG RMS (p>0.05) and greater EMG MPF (p<0.05) values were recorded over the IZ compared to away from the IZ, however, no differences in slope coefficients for the EMG RMS and MPF versus time relationships over, proximal, and distal to the IZ occurred. Thus, the results of the present study indicated that during an MVIC, EMG RMS and MPF values recorded over the IZ are not comparable to those away from the IZ. However, the rates of fatigue-induced changes in EMG RMS and MPF during sustained, submaximal isometric muscle actions of the leg extensors were the same regardless of the electrode placement locations relative to the IZ.

Research paper thumbnail of Normalization of supine blood pressure after nitric oxide synthase inhibition in persons with tetraplegia

The journal of spinal cord medicine, 2007

Orthostatic hypotension is a well-defined clinical consequence of spinal cord injury (SCI), parti... more Orthostatic hypotension is a well-defined clinical consequence of spinal cord injury (SCI), particularly in those with tetraplegia. The etiology of orthostatic hypotension is thought to be loss of sympathetic vasomotor control, although other factors may play a role. There is evidence of up-regulation of nitric oxide synthase (NOS) activity after hind-limb suspension in rats, a condition of antigravity that may have similar vascular effects as shown in persons with tetraplegia caused by paralysis. The study objective was to determine the effect of a NOS inhibitor (nitro-L-arginine methyl ester [L-NAME]) on supine mean arterial pressure in persons with chronic tetraplegia compared with non-SCI controls. Fourteen individuals participated (7 with tetraplegia and 7 controls). Subjects visited the laboratory twice for placebo on day 1 and L-NAME (1 mg/kg) on day 2; both were infused intravenously over 60 minutes. Blood pressure was monitored for 3 hours after infusion at the brachial art...

Research paper thumbnail of The effect of pedaling cadence and power output on mechanomyographic amplitude and mean power frequency during submaximal cycle ergometry

Electromyography and clinical neurophysiology

The purpose of this study was to examine the effects of power output and pedaling cadence on the ... more The purpose of this study was to examine the effects of power output and pedaling cadence on the amplitude and mean power frequency (MPF) of the mechanomyographic (MMG) signal during submaximal cycle ergometry. Nine adults (mean age +/- SD = 22.7 +/- 2.1 yrs) performed an incremental (25 W increase every min) test to exhaustion on an electronically braked cycle ergometer to determine VO2Peak and Wpeak. The subjects also performed three, 8 min continuous, constant power output rides (randomly ordered) at 35%, 50%, and 65% Wpeak. The continuous 8 min workbouts were divided into 4 min epochs. The subjects pedaled at either 50 or 70 rev x min(-1) (randomized) during the first 4 min epoch, then changed to the alternate cadence during the second 4 min epoch. The MMG signal was recorded from the vastus lateralis during the final 10 s of each minute. Two separate two-way [cadence (50 and 70 rev x min(-1)) x %Wpeak (35, 50, and 65)] repeated measures ANOVAs indicated that MMG amplitude follo...

Research paper thumbnail of Gender comparisons of mechanomyographic amplitude and mean power frequency versus isometric torque relationships

Journal of applied biomechanics, 2005

This study compared the patterns of mechanomyographic (MMG) amplitude and mean power frequency vs... more This study compared the patterns of mechanomyographic (MMG) amplitude and mean power frequency vs. torque relationships in men and women during isometric muscle actions of the biceps brachii. Seven men (mean age 23.9 +/- 3.5 yrs) and 8 women (mean 21.0 +/- 1.3 yrs) performed submaximal to maximal isometric muscle actions of the dominant forearm flexors. Following determination of the isometric maximum voluntary contraction (MVC), they randomly performed submaximal step muscle actions in 10% increments from 10% to 90% MVC. Polynomial regression analyses indicated that the MMG amplitude vs. isometric torque relationship for the men was best fit with a cubic model (R(2) = 0.983),,where MMG amplitude increased slightly from 10% to 20% MVC, increased rapidly from 20% to 80% MVC, and plateaued from 80% to 100% MVC. For the women, MMG amplitude increased linearly (r(2) = 0.949) from 10% to 100% MVC. Linear models also provided the best fit for the MMG mean power frequency vs. isometric tor...

Research paper thumbnail of Arterial stiffness in persons with paraplegia

The journal of spinal cord medicine, 2004

Arterial stiffness recently has been identified as an independent risk factor for cardiovascular ... more Arterial stiffness recently has been identified as an independent risk factor for cardiovascular disease. An accurate and noninvasive estimate of arterial stiffness can be made through close examination of the pulse wave contour, and is expressed as the augmentation index (AI). Increased stiffness is associated with increased systolic blood pressure (SBP), pulse pressure, and reduced baroreceptor sensitivity. The purpose of this study was to compare the common carotid AI in participants with paraplegia vs able-bodied controls as well as compare group differences for blood pressure while supine and in response to gravitational stress. Study participants were 19 healthy individuals with paraplegia (below T6) and 9 able-bodied controls matched for age, height, and weight. An electronic tilt table was used for testing responses to gravitational stress at 4 angles (-10 degrees, 10 degrees, 35 degrees, and 75 degrees). AI was assessed at each angle of tilt using an externally applied high...

Research paper thumbnail of Mechanomyographic time and frequency domain responses of the vastus medialis muscle during submaximal to maximal isometric and isokinetic muscle actions

Electromyography and clinical neurophysiology, 2004

The purpose of this study was to examine the patterns for the mechanomyographic (MMG) amplitude a... more The purpose of this study was to examine the patterns for the mechanomyographic (MMG) amplitude and mean power frequency (MPF) versus torque relationships during isometric and isokinetic muscle actions. Ten adults (mean age +/- SD = 22 +/- 1 y) volunteered to perform isometric and isokinetic leg extension muscle actions at 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100% of peak torque on a Cybex II dynamometer. A piezoelectric crystal contact sensor was placed on the vastus medialis to detect the MMG signal. Regression analyses indicated that for the isometric muscle actions, the relationships for MMG amplitude (R2 = 0.998) and MPF (R2 = 0.987) versus torque were cubic. For the isokinetic muscle actions, the relationships for MMG amplitude (r2 = 0.927) and MPF (r2 = 0.769) versus torque were linear. The different patterns for MMG amplitude and frequency may reflect differences in the motor control strategies that modulate torque production for isometric versus dynamic muscle actions.

Research paper thumbnail of Cardiac autonomic responses to progressive head-up tilt in individuals with paraplegia

Clinical autonomic research : official journal of the Clinical Autonomic Research Society, 2003

Beat-to-beat fluctuations in heart rate are partially controlled by the autonomic nervous system ... more Beat-to-beat fluctuations in heart rate are partially controlled by the autonomic nervous system and may be altered by a spinal cord injury. The purpose of the present investigation was to examine the role of the autonomic nervous system in modulating the heart rate response to head-up tilt (HUT) in subjects with low lesion paraplegia. Nineteen subjects with paraplegia and nine age-, height-, and weight-matched control subjects consented to participate. A three lead ECG was used to acquire heart rate (HR), cardiac sympathetic [low frequency component of R-R interval variability (LFRRI)], vagal [high frequency component of R-R interval variability (HFRRI)] and sympatho-vagal balance (LF/HF). A finger photoplethysmograph was used to assess beat-to-beat blood pressure for the estimation of sympathetic vasomotor tone [low frequency component of peak systolic blood pressure variability (LFSBP)]. The results showed a significant main effect for tilt angle for the HR response to HUT, which...

Research paper thumbnail of Cardiac homeostasis is independent of calf venous compliance in subjects with paraplegia

American journal of physiology. Heart and circulatory physiology, 2003

The purpose of this study was to examine cardiac hemodynamics during acute head-up tilt (HUT) and... more The purpose of this study was to examine cardiac hemodynamics during acute head-up tilt (HUT) and calf venous function during acute head-down tilt (HDT) in subjects with paraplegia compared with sedentary nondisabled controls. Nineteen paraplegic males (below T6) and nine age-, height-, and weight-matched control subjects participated. Heart rate, stroke volume, and cardiac output were assessed using the noninvasive acetylene uptake method. Venous vascular function of the calf was assessed using venous occlusion plethysmography. After supine measurements were collected, the table was moved to 10 degrees HDT followed by the three levels of HUT (10, 35, and 75 degrees ) in random order. Cardiac hemodynamics were similar between the groups at all positions. Calf circumference was significantly reduced in the paraplegic group compared with the control group (P < 0.001). Venous capacitance and compliance were significantly reduced in the paraplegic compared with control group at supin...

Research paper thumbnail of The influence of electromyographic recording methods and the innervation zone on the mean power frequency-torque relationships

Journal of Electromyography and Kinesiology, 2015

This study examined the effects of electromyographic (EMG) recording methods and innervation zone... more This study examined the effects of electromyographic (EMG) recording methods and innervation zone (IZ) on the mean power frequency (MPF)-torque relationships. Nine subjects performed isometric ramp muscle actions of the leg extensors from 5% to 100% of maximal voluntary contraction with an eight channel linear electrode array over the IZ of the vastus lateralis. The slopes were calculated from the log-transformed monopolar and bipolar EMG MPF-torque relationships for each channel and subject and 95% confidence intervals (CI) were constructed around the slopes for each relationship and the composite of the slopes. Twenty-two to 55% of the subjects exhibited 95% CIs that did not include a slope of zero for the monopolar EMG MPF-torque relationships while 25-75% of the subjects exhibited 95% CIs that did not include a slope of zero for the bipolar EMG MPF-torque relationships. The composite of the slopes from the EMG MPF-torque relationships were not significantly different from zero for any method or channel, however, the method and IZ location slightly influenced the number of significant slopes on a subject-by-subject basis. The log-transform model indicated that EMG MPF-torque patterns were nonlinear regardless of recording method or distance from the IZ.

Research paper thumbnail of Estrogen replacement, vascular distensibility, and blood pressures in postmenopausal women

The American journal of physiology, 1998

The pathogenesis of blood pressure (BP) rise in aging women remains unexplained, and one of the m... more The pathogenesis of blood pressure (BP) rise in aging women remains unexplained, and one of the many incriminating factors may include abnormalities in arteriolar resistance vessels. The aim of this study was to determine the effects of unopposed estrogen on arteriolar distensibility, baroreceptor sensitivity (BRS), BP changes, and rate-pressure product (RPP). We tested the hypotheses that estrogen replacement therapy (ERT) enhances arteriolar distensibility and ameliorates BRS, which leads to decreases in BP and RPP. Postmenopausal women participated in a single-blind crossover study; the participants of this study, after baseline measurements, were randomly assigned to receive estrogen (ERT) or a drug-free treatment with a 6-wk washout period between treatments. The single-blind design was instituted because subjects become unblinded due to physiological changes (i.e., fluid shifts, weight gain, and secretory changes) associated with estrogen intake. However, investigators and tec...

Research paper thumbnail of Effects of unilateral concentric-only dynamic constant external resistance training

International journal of sports medicine, 1996

The purposes of this investigation were to examine the effects of unilateral concentric-only leg ... more The purposes of this investigation were to examine the effects of unilateral concentric-only leg extension dynamic constant external resistance (DCER) training on: (a) concentric DCER strength in the trained and contralateral (untrained) legs, (b) concentric isokinetic peak torque-velocity curves in the trained and contralateral legs, and (c) retention of concentric DCER strength and concentric isokinetic peak torque in the trained and contralateral legs following detraining. Sixteen adult male (mean age +/- SD = 24.0 +/- 4.0 yr) volunteers comprised training (TR, n = 8) and control (CTL, n = 8) groups. The TR group trained the nondominant limb with concentric-only leg extension DCER exercise (3-5 sets of 6 repetitions at 80% of one-repetition maximum load) for eight weeks followed by eight additional weeks of detraining. The CTL group did not train. All subjects were tested pretraining, posttraining and detraining for unilateral concentric-only leg extension DCER strength as well a...

Research paper thumbnail of Effects of eccentric-only resistance training and detraining

International journal of sports medicine, 1996

The purposes of this investigation were to examine the effects of unilateral eccentric-only dynam... more The purposes of this investigation were to examine the effects of unilateral eccentric-only dynamic constant external resistance (DCER) training of the leg extensor muscles on: (a) eccentric DCER strength in the trained and untrained limbs, (b) concentric isokinetic leg extension peak torque-velocity curves in the trained and untrained limbs, and (c) retention of eccentric DCER strength and concentric isokinetic peak torque in the trained and untrained limbs following detraining. Seventeen adult male (X age +/- SD = 24 +/- 3 yr) volunteers comprised training (TR, n = 9) and control (CTL, n = 8) groups. The TR group trained the leg extensor muscles of the nondominant limb with eccentric-only DCER exercise (3 - 5 sets of 6 repetitions at 80% of the eccentric one-repetition maximum [1-RM] load) for eight weeks followed by eight additional weeks of detraining. The CTL group did not train. All subjects were tested pretraining, posttraining, and after detraining for 1-RM unilateral eccent...

Research paper thumbnail of Electromyographic evaluation of joint angle specificity and cross-training after isometric training

Journal of applied physiology (Bethesda, Md. : 1985), 1994

The purpose of this study was to examine the effects of unilateral strength training on the stren... more The purpose of this study was to examine the effects of unilateral strength training on the strength and integrated electromyogram (IEMG) of the trained and untrained limbs at several joint angles. A training group [TRN; 4 females and 3 males, age 22 +/- 4 yr (SD)] exercised for 6 wk with isometric leg extensions at 80% of maximal isometric torque. A control group (3 females and 3 males, age 24 +/- 4 yr) did not exercise. The training was performed three times per week at 0.79 rad below the horizontal plane. The subjects were tested at joint angles of 0.00, 0.26, 0.79, 1.31, and 1.57 rad. Bipolar surface electrodes were used to record the IEMG of the vastus lateralis. The results indicated a cross-training effect and joint angle specificity for isometric torque in TRN only, with significant (P < 0.0005) increases in torque (collapsed across limb) at 0.26 (23.3%) and 0.79 (22.3%) rad. There was a dissociation, however, between changes in torque and IEMG with an increase (P < 0....

Research paper thumbnail of Motor unit control strategies of endurance versus resistance trained individuals

Muscle & Nerve, 2015

Introduction: We examined motor unit (MU) control properties of resistance- (RT) and endurance-tr... more Introduction: We examined motor unit (MU) control properties of resistance- (RT) and endurance-trained (ET) individuals. Methods: Five RT (age=25±4 yrs) and 5 ET (age=19±1 yrs) participated. Surface electromyographic (EMG) was recorded from the vastus lateralis during isometric trapezoid muscle actions at 40% and 70% of maximal voluntary contraction. Decomposition and wavelet transform techniques were applied to the EMG signals to extract the firing events of single MUs and EMG intensity across the frequency spectrum. Results: There were significant differences between RT and ET for the mean MU firing rate and derecruitment threshold versus recruitment threshold relationships and EMG intensity at various wavelet bands during the linearly increasing, steady force, and linearly decreasing segments of the trapezoid contraction. Discussion: MU behavior is altered as a function of training status and likely is the result of differences in the physical properties of the MU. This article is protected by copyright. All rights reserved.

Research paper thumbnail of Relationships of Age and Muscle Mass to Peak Torque in High School Wrestlers

Research Quarterly for Exercise and Sport, 1995

Research paper thumbnail of A prospective report on the prevalence of heart rate and blood pressure abnormalities in veterans with spinal cord injuries

The Journal of Spinal Cord Medicine, 2013

Decentralized autonomic cardiovascular regulation may lead to increased prevalence of heart rate ... more Decentralized autonomic cardiovascular regulation may lead to increased prevalence of heart rate (HR) and blood pressure (BP) abnormalities in veterans with SCI. In addition, comorbid medical conditions and prescription medication use may increase HR and BP abnormalities. These abnormalities include bradycardia, and tachycardia, hypotension, hypertension as well as autonomic dysreflexia and orthostatic hypotension; the prevalence of which is unknown. HR and BP data were measured during a routine annual physical examination in 64 veterans with SCI. Measurements of HR and BP were recorded in the seated and supine positions to document the influence of body position and to document intra-subject variability in these assessments. All subjects were chronically injured (20 ± 14 years), 33 subjects were tetraplegic (T: C3-C8), nine had high paraplegia (HP: T1-T6), and 22 had low paraplegia (LP: T7-L2). Regardless of position, the prevalence of bradycardia was increased in the T group, whereas prevalence of tachycardia was increased in the HP and LP groups. Systolic hypotension was more common in the T and HP groups than the LP group and positional effects were most evident in the T group. Systolic hypertension was comparable in the T and HP groups but was twice as prevalent in the LP group. Increased prevalence of individuals with three or more medical conditions and prescribed three or more medications which might influence HR and BP was observed. Decentralized autonomic regulation, comorbid medical conditions, and prescription medication use in veterans with SCI result in HR and BP abnormalities; our data suggest that these abnormalities vary depending on the level of injury and orthostatic positioning.

Research paper thumbnail of ASEP Procedures Recommendation ASEP PROCEDURES RECOMMENDATION I: ACCURATE ASSESSMENT OF MUSCULAR STRENGTH AND POWER

... Procedures During testing, the subject is asked to pedal against a pre-selected opposing resi... more ... Procedures During testing, the subject is asked to pedal against a pre-selected opposing resistance ... For example, shoulder motion from zero to 90 degrees and from 90 to 180 degrees of ... from 60 through 360 °/s, which may be explained through decreased activation of primarily ...

Research paper thumbnail of Recomendação de procedimentos da Sociedade Americana de Fisiologia do Exercício (ASEP) I: avaliação precisa da força e potência muscular; Procedures …

Rev. bras. ciênc. …, 2003

Base de dados : LILACS. Pesquisa : 524937 [Identificador único]. Referências encontradas : 1 [ref... more Base de dados : LILACS. Pesquisa : 524937 [Identificador único]. Referências encontradas : 1 [refinar]. Mostrando: 1 .. 1 no formato [Detalhado]. página 1 de 1, 1 / 1, LILACS, seleciona. para imprimir. Fotocópia. Texto completo. experimental, Documentos relacionados. Id: 524937 ...

Research paper thumbnail of Effects of Unilateral Concentric-Only Dynamic Constant External Resistance Training on Quadriceps Femoris Cross-Sectional Area

Journal of Strength and Conditioning Research, 1998

The purposes of this investigation were to examine the effects of unilateral concentric-only leg ... more The purposes of this investigation were to examine the effects of unilateral concentric-only leg extension dynamic constant external resistance (DCER) training on: (a) concentric DCER strength in the trained and contralateral (untrained) legs, (b) concentric isokinetic peak torque-velocity curves in the trained and contralateral legs, and (c) retention of concentric DCER strength and concentric isokinetic peak torque in the trained and contralateral legs following detraining. Sixteen adult male (mean age +/- SD = 24.0 +/- 4.0 yr) volunteers comprised training (TR, n = 8) and control (CTL, n = 8) groups. The TR group trained the nondominant limb with concentric-only leg extension DCER exercise (3-5 sets of 6 repetitions at 80% of one-repetition maximum load) for eight weeks followed by eight additional weeks of detraining. The CTL group did not train. All subjects were tested pretraining, posttraining and detraining for unilateral concentric-only leg extension DCER strength as well as concentric isokinetic peak torque at 1.05, 2.09, 3.14, 4.19, and 5.24 rad.s-1 in both legs. Mixed factorial ANOVAs, follow-up, and post-hoc analyses indicated that the training resulted in increased DCER strength in both the trained (42%) and contralateral (15%) legs as well as isokinetic peak torque in the trained leg (7-19%) at velocities ranging from 1.05 to 5.24 rad.s-1. There was no cross-training effect, however, for isokinetic peak torque. Furthermore, the training-induced increases in DCER strength and isokinetic peak torque were retained across eight weeks of detraining.

Research paper thumbnail of Isokinetic Dynamometry in Healthy Versus Sarcopenic and Malnourished Elderly: Beyond Simple Measurements of Muscle Strength

Journal of applied gerontology : the official journal of the Southern Gerontological Society, Jan 5, 2015

This study quantified systematic and intraindividual variability among three repetitions of conce... more This study quantified systematic and intraindividual variability among three repetitions of concentric isokinetic knee extension and flexion tests to determine velocity-related differences in peak torque (PT) and mean power (MP) in healthy elderly (HE) versus sarcopenic and malnourished elderly (SME). In total, 107 HE (n = 54 men, n = 53 women) and 261 SME (n = 101 men, n = 160 women) performed three maximal concentric isokinetic knee extension and flexion repetitions at 60°·s(-1) and 180°·s(-1). PT for Repetition 3 was lower than Repetitions 1 and 2, while MP for Repetition 1 was lower than Repetitions 2 and 3 in SME. Intraindividual variability among repetitions was correlated with strength, but not age, and was greater in SME, during knee flexion, and at 180°·s(-1). Velocity-related decreases in PT from 60°·s(-1) to 180°·s(-1) were more pronounced in SME. In summary, (a) the repetition with the highest PT value may be the best indicator of maximal strength, while the average may ...

Research paper thumbnail of Effects of the innervation zone on the time and frequency domain parameters of the surface electromyographic signal

Journal of Electromyography and Kinesiology, 2015

The purposes of the present study were to examine the effects of electrode placements over, proxi... more The purposes of the present study were to examine the effects of electrode placements over, proximal, and distal to the innervation zone (IZ) on electromyographic (EMG) amplitude (RMS) and frequency (MPF) responses during: (1) a maximal voluntary isometric contraction (MVIC), and; (2) a sustained, submaximal isometric muscle action. A linear array was used to record EMG signals from the vastus lateralis over the IZ, 30mm proximal, and 30mm distal to the IZ during an MVIC and a sustained isometric muscle action of the leg extensors at 50% MVIC. During the MVIC, lower EMG RMS (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;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;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;0.05) and greater EMG MPF (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;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;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) values were recorded over the IZ compared to away from the IZ, however, no differences in slope coefficients for the EMG RMS and MPF versus time relationships over, proximal, and distal to the IZ occurred. Thus, the results of the present study indicated that during an MVIC, EMG RMS and MPF values recorded over the IZ are not comparable to those away from the IZ. However, the rates of fatigue-induced changes in EMG RMS and MPF during sustained, submaximal isometric muscle actions of the leg extensors were the same regardless of the electrode placement locations relative to the IZ.

Research paper thumbnail of Normalization of supine blood pressure after nitric oxide synthase inhibition in persons with tetraplegia

The journal of spinal cord medicine, 2007

Orthostatic hypotension is a well-defined clinical consequence of spinal cord injury (SCI), parti... more Orthostatic hypotension is a well-defined clinical consequence of spinal cord injury (SCI), particularly in those with tetraplegia. The etiology of orthostatic hypotension is thought to be loss of sympathetic vasomotor control, although other factors may play a role. There is evidence of up-regulation of nitric oxide synthase (NOS) activity after hind-limb suspension in rats, a condition of antigravity that may have similar vascular effects as shown in persons with tetraplegia caused by paralysis. The study objective was to determine the effect of a NOS inhibitor (nitro-L-arginine methyl ester [L-NAME]) on supine mean arterial pressure in persons with chronic tetraplegia compared with non-SCI controls. Fourteen individuals participated (7 with tetraplegia and 7 controls). Subjects visited the laboratory twice for placebo on day 1 and L-NAME (1 mg/kg) on day 2; both were infused intravenously over 60 minutes. Blood pressure was monitored for 3 hours after infusion at the brachial art...

Research paper thumbnail of The effect of pedaling cadence and power output on mechanomyographic amplitude and mean power frequency during submaximal cycle ergometry

Electromyography and clinical neurophysiology

The purpose of this study was to examine the effects of power output and pedaling cadence on the ... more The purpose of this study was to examine the effects of power output and pedaling cadence on the amplitude and mean power frequency (MPF) of the mechanomyographic (MMG) signal during submaximal cycle ergometry. Nine adults (mean age +/- SD = 22.7 +/- 2.1 yrs) performed an incremental (25 W increase every min) test to exhaustion on an electronically braked cycle ergometer to determine VO2Peak and Wpeak. The subjects also performed three, 8 min continuous, constant power output rides (randomly ordered) at 35%, 50%, and 65% Wpeak. The continuous 8 min workbouts were divided into 4 min epochs. The subjects pedaled at either 50 or 70 rev x min(-1) (randomized) during the first 4 min epoch, then changed to the alternate cadence during the second 4 min epoch. The MMG signal was recorded from the vastus lateralis during the final 10 s of each minute. Two separate two-way [cadence (50 and 70 rev x min(-1)) x %Wpeak (35, 50, and 65)] repeated measures ANOVAs indicated that MMG amplitude follo...

Research paper thumbnail of Gender comparisons of mechanomyographic amplitude and mean power frequency versus isometric torque relationships

Journal of applied biomechanics, 2005

This study compared the patterns of mechanomyographic (MMG) amplitude and mean power frequency vs... more This study compared the patterns of mechanomyographic (MMG) amplitude and mean power frequency vs. torque relationships in men and women during isometric muscle actions of the biceps brachii. Seven men (mean age 23.9 +/- 3.5 yrs) and 8 women (mean 21.0 +/- 1.3 yrs) performed submaximal to maximal isometric muscle actions of the dominant forearm flexors. Following determination of the isometric maximum voluntary contraction (MVC), they randomly performed submaximal step muscle actions in 10% increments from 10% to 90% MVC. Polynomial regression analyses indicated that the MMG amplitude vs. isometric torque relationship for the men was best fit with a cubic model (R(2) = 0.983),,where MMG amplitude increased slightly from 10% to 20% MVC, increased rapidly from 20% to 80% MVC, and plateaued from 80% to 100% MVC. For the women, MMG amplitude increased linearly (r(2) = 0.949) from 10% to 100% MVC. Linear models also provided the best fit for the MMG mean power frequency vs. isometric tor...

Research paper thumbnail of Arterial stiffness in persons with paraplegia

The journal of spinal cord medicine, 2004

Arterial stiffness recently has been identified as an independent risk factor for cardiovascular ... more Arterial stiffness recently has been identified as an independent risk factor for cardiovascular disease. An accurate and noninvasive estimate of arterial stiffness can be made through close examination of the pulse wave contour, and is expressed as the augmentation index (AI). Increased stiffness is associated with increased systolic blood pressure (SBP), pulse pressure, and reduced baroreceptor sensitivity. The purpose of this study was to compare the common carotid AI in participants with paraplegia vs able-bodied controls as well as compare group differences for blood pressure while supine and in response to gravitational stress. Study participants were 19 healthy individuals with paraplegia (below T6) and 9 able-bodied controls matched for age, height, and weight. An electronic tilt table was used for testing responses to gravitational stress at 4 angles (-10 degrees, 10 degrees, 35 degrees, and 75 degrees). AI was assessed at each angle of tilt using an externally applied high...

Research paper thumbnail of Mechanomyographic time and frequency domain responses of the vastus medialis muscle during submaximal to maximal isometric and isokinetic muscle actions

Electromyography and clinical neurophysiology, 2004

The purpose of this study was to examine the patterns for the mechanomyographic (MMG) amplitude a... more The purpose of this study was to examine the patterns for the mechanomyographic (MMG) amplitude and mean power frequency (MPF) versus torque relationships during isometric and isokinetic muscle actions. Ten adults (mean age +/- SD = 22 +/- 1 y) volunteered to perform isometric and isokinetic leg extension muscle actions at 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100% of peak torque on a Cybex II dynamometer. A piezoelectric crystal contact sensor was placed on the vastus medialis to detect the MMG signal. Regression analyses indicated that for the isometric muscle actions, the relationships for MMG amplitude (R2 = 0.998) and MPF (R2 = 0.987) versus torque were cubic. For the isokinetic muscle actions, the relationships for MMG amplitude (r2 = 0.927) and MPF (r2 = 0.769) versus torque were linear. The different patterns for MMG amplitude and frequency may reflect differences in the motor control strategies that modulate torque production for isometric versus dynamic muscle actions.

Research paper thumbnail of Cardiac autonomic responses to progressive head-up tilt in individuals with paraplegia

Clinical autonomic research : official journal of the Clinical Autonomic Research Society, 2003

Beat-to-beat fluctuations in heart rate are partially controlled by the autonomic nervous system ... more Beat-to-beat fluctuations in heart rate are partially controlled by the autonomic nervous system and may be altered by a spinal cord injury. The purpose of the present investigation was to examine the role of the autonomic nervous system in modulating the heart rate response to head-up tilt (HUT) in subjects with low lesion paraplegia. Nineteen subjects with paraplegia and nine age-, height-, and weight-matched control subjects consented to participate. A three lead ECG was used to acquire heart rate (HR), cardiac sympathetic [low frequency component of R-R interval variability (LFRRI)], vagal [high frequency component of R-R interval variability (HFRRI)] and sympatho-vagal balance (LF/HF). A finger photoplethysmograph was used to assess beat-to-beat blood pressure for the estimation of sympathetic vasomotor tone [low frequency component of peak systolic blood pressure variability (LFSBP)]. The results showed a significant main effect for tilt angle for the HR response to HUT, which...

Research paper thumbnail of Cardiac homeostasis is independent of calf venous compliance in subjects with paraplegia

American journal of physiology. Heart and circulatory physiology, 2003

The purpose of this study was to examine cardiac hemodynamics during acute head-up tilt (HUT) and... more The purpose of this study was to examine cardiac hemodynamics during acute head-up tilt (HUT) and calf venous function during acute head-down tilt (HDT) in subjects with paraplegia compared with sedentary nondisabled controls. Nineteen paraplegic males (below T6) and nine age-, height-, and weight-matched control subjects participated. Heart rate, stroke volume, and cardiac output were assessed using the noninvasive acetylene uptake method. Venous vascular function of the calf was assessed using venous occlusion plethysmography. After supine measurements were collected, the table was moved to 10 degrees HDT followed by the three levels of HUT (10, 35, and 75 degrees ) in random order. Cardiac hemodynamics were similar between the groups at all positions. Calf circumference was significantly reduced in the paraplegic group compared with the control group (P < 0.001). Venous capacitance and compliance were significantly reduced in the paraplegic compared with control group at supin...

Research paper thumbnail of The influence of electromyographic recording methods and the innervation zone on the mean power frequency-torque relationships

Journal of Electromyography and Kinesiology, 2015

This study examined the effects of electromyographic (EMG) recording methods and innervation zone... more This study examined the effects of electromyographic (EMG) recording methods and innervation zone (IZ) on the mean power frequency (MPF)-torque relationships. Nine subjects performed isometric ramp muscle actions of the leg extensors from 5% to 100% of maximal voluntary contraction with an eight channel linear electrode array over the IZ of the vastus lateralis. The slopes were calculated from the log-transformed monopolar and bipolar EMG MPF-torque relationships for each channel and subject and 95% confidence intervals (CI) were constructed around the slopes for each relationship and the composite of the slopes. Twenty-two to 55% of the subjects exhibited 95% CIs that did not include a slope of zero for the monopolar EMG MPF-torque relationships while 25-75% of the subjects exhibited 95% CIs that did not include a slope of zero for the bipolar EMG MPF-torque relationships. The composite of the slopes from the EMG MPF-torque relationships were not significantly different from zero for any method or channel, however, the method and IZ location slightly influenced the number of significant slopes on a subject-by-subject basis. The log-transform model indicated that EMG MPF-torque patterns were nonlinear regardless of recording method or distance from the IZ.

Research paper thumbnail of Estrogen replacement, vascular distensibility, and blood pressures in postmenopausal women

The American journal of physiology, 1998

The pathogenesis of blood pressure (BP) rise in aging women remains unexplained, and one of the m... more The pathogenesis of blood pressure (BP) rise in aging women remains unexplained, and one of the many incriminating factors may include abnormalities in arteriolar resistance vessels. The aim of this study was to determine the effects of unopposed estrogen on arteriolar distensibility, baroreceptor sensitivity (BRS), BP changes, and rate-pressure product (RPP). We tested the hypotheses that estrogen replacement therapy (ERT) enhances arteriolar distensibility and ameliorates BRS, which leads to decreases in BP and RPP. Postmenopausal women participated in a single-blind crossover study; the participants of this study, after baseline measurements, were randomly assigned to receive estrogen (ERT) or a drug-free treatment with a 6-wk washout period between treatments. The single-blind design was instituted because subjects become unblinded due to physiological changes (i.e., fluid shifts, weight gain, and secretory changes) associated with estrogen intake. However, investigators and tec...

Research paper thumbnail of Effects of unilateral concentric-only dynamic constant external resistance training

International journal of sports medicine, 1996

The purposes of this investigation were to examine the effects of unilateral concentric-only leg ... more The purposes of this investigation were to examine the effects of unilateral concentric-only leg extension dynamic constant external resistance (DCER) training on: (a) concentric DCER strength in the trained and contralateral (untrained) legs, (b) concentric isokinetic peak torque-velocity curves in the trained and contralateral legs, and (c) retention of concentric DCER strength and concentric isokinetic peak torque in the trained and contralateral legs following detraining. Sixteen adult male (mean age +/- SD = 24.0 +/- 4.0 yr) volunteers comprised training (TR, n = 8) and control (CTL, n = 8) groups. The TR group trained the nondominant limb with concentric-only leg extension DCER exercise (3-5 sets of 6 repetitions at 80% of one-repetition maximum load) for eight weeks followed by eight additional weeks of detraining. The CTL group did not train. All subjects were tested pretraining, posttraining and detraining for unilateral concentric-only leg extension DCER strength as well a...

Research paper thumbnail of Effects of eccentric-only resistance training and detraining

International journal of sports medicine, 1996

The purposes of this investigation were to examine the effects of unilateral eccentric-only dynam... more The purposes of this investigation were to examine the effects of unilateral eccentric-only dynamic constant external resistance (DCER) training of the leg extensor muscles on: (a) eccentric DCER strength in the trained and untrained limbs, (b) concentric isokinetic leg extension peak torque-velocity curves in the trained and untrained limbs, and (c) retention of eccentric DCER strength and concentric isokinetic peak torque in the trained and untrained limbs following detraining. Seventeen adult male (X age +/- SD = 24 +/- 3 yr) volunteers comprised training (TR, n = 9) and control (CTL, n = 8) groups. The TR group trained the leg extensor muscles of the nondominant limb with eccentric-only DCER exercise (3 - 5 sets of 6 repetitions at 80% of the eccentric one-repetition maximum [1-RM] load) for eight weeks followed by eight additional weeks of detraining. The CTL group did not train. All subjects were tested pretraining, posttraining, and after detraining for 1-RM unilateral eccent...

Research paper thumbnail of Electromyographic evaluation of joint angle specificity and cross-training after isometric training

Journal of applied physiology (Bethesda, Md. : 1985), 1994

The purpose of this study was to examine the effects of unilateral strength training on the stren... more The purpose of this study was to examine the effects of unilateral strength training on the strength and integrated electromyogram (IEMG) of the trained and untrained limbs at several joint angles. A training group [TRN; 4 females and 3 males, age 22 +/- 4 yr (SD)] exercised for 6 wk with isometric leg extensions at 80% of maximal isometric torque. A control group (3 females and 3 males, age 24 +/- 4 yr) did not exercise. The training was performed three times per week at 0.79 rad below the horizontal plane. The subjects were tested at joint angles of 0.00, 0.26, 0.79, 1.31, and 1.57 rad. Bipolar surface electrodes were used to record the IEMG of the vastus lateralis. The results indicated a cross-training effect and joint angle specificity for isometric torque in TRN only, with significant (P < 0.0005) increases in torque (collapsed across limb) at 0.26 (23.3%) and 0.79 (22.3%) rad. There was a dissociation, however, between changes in torque and IEMG with an increase (P < 0....

Research paper thumbnail of Motor unit control strategies of endurance versus resistance trained individuals

Muscle & Nerve, 2015

Introduction: We examined motor unit (MU) control properties of resistance- (RT) and endurance-tr... more Introduction: We examined motor unit (MU) control properties of resistance- (RT) and endurance-trained (ET) individuals. Methods: Five RT (age=25±4 yrs) and 5 ET (age=19±1 yrs) participated. Surface electromyographic (EMG) was recorded from the vastus lateralis during isometric trapezoid muscle actions at 40% and 70% of maximal voluntary contraction. Decomposition and wavelet transform techniques were applied to the EMG signals to extract the firing events of single MUs and EMG intensity across the frequency spectrum. Results: There were significant differences between RT and ET for the mean MU firing rate and derecruitment threshold versus recruitment threshold relationships and EMG intensity at various wavelet bands during the linearly increasing, steady force, and linearly decreasing segments of the trapezoid contraction. Discussion: MU behavior is altered as a function of training status and likely is the result of differences in the physical properties of the MU. This article is protected by copyright. All rights reserved.

Research paper thumbnail of Relationships of Age and Muscle Mass to Peak Torque in High School Wrestlers

Research Quarterly for Exercise and Sport, 1995

Research paper thumbnail of A prospective report on the prevalence of heart rate and blood pressure abnormalities in veterans with spinal cord injuries

The Journal of Spinal Cord Medicine, 2013

Decentralized autonomic cardiovascular regulation may lead to increased prevalence of heart rate ... more Decentralized autonomic cardiovascular regulation may lead to increased prevalence of heart rate (HR) and blood pressure (BP) abnormalities in veterans with SCI. In addition, comorbid medical conditions and prescription medication use may increase HR and BP abnormalities. These abnormalities include bradycardia, and tachycardia, hypotension, hypertension as well as autonomic dysreflexia and orthostatic hypotension; the prevalence of which is unknown. HR and BP data were measured during a routine annual physical examination in 64 veterans with SCI. Measurements of HR and BP were recorded in the seated and supine positions to document the influence of body position and to document intra-subject variability in these assessments. All subjects were chronically injured (20 ± 14 years), 33 subjects were tetraplegic (T: C3-C8), nine had high paraplegia (HP: T1-T6), and 22 had low paraplegia (LP: T7-L2). Regardless of position, the prevalence of bradycardia was increased in the T group, whereas prevalence of tachycardia was increased in the HP and LP groups. Systolic hypotension was more common in the T and HP groups than the LP group and positional effects were most evident in the T group. Systolic hypertension was comparable in the T and HP groups but was twice as prevalent in the LP group. Increased prevalence of individuals with three or more medical conditions and prescribed three or more medications which might influence HR and BP was observed. Decentralized autonomic regulation, comorbid medical conditions, and prescription medication use in veterans with SCI result in HR and BP abnormalities; our data suggest that these abnormalities vary depending on the level of injury and orthostatic positioning.

Research paper thumbnail of ASEP Procedures Recommendation ASEP PROCEDURES RECOMMENDATION I: ACCURATE ASSESSMENT OF MUSCULAR STRENGTH AND POWER

... Procedures During testing, the subject is asked to pedal against a pre-selected opposing resi... more ... Procedures During testing, the subject is asked to pedal against a pre-selected opposing resistance ... For example, shoulder motion from zero to 90 degrees and from 90 to 180 degrees of ... from 60 through 360 °/s, which may be explained through decreased activation of primarily ...