Physical Therapy Commons^™

Sex Differences In Time To Task Failure And Blood Flow For An Intermittent Isometric Fatiguing Contraction, Sandra K. Hunter, Erin E. Griffith, Kristine M. Schlachter, Tim D. Kufahl

Exercise Science Faculty Research and Publications

The purpose of this study was to compare the time to task failure, postcontraction hyperemia, and vascular conductance of young men and women for a submaximal intermittent fatiguing contraction performed with the handgrip muscles. Twenty men and 20 women (mean SD: 22 4 years) performed an isometric contraction at 50% of maximal voluntary contraction (MVC) (6-s contraction, 4-s rest) until task failure. Forearm venous occlusion plethysmography was used to estimate the peak blood flow (after 10-min occlusion) and blood flow at rest after 6-s submaximal contractions of varying intensities, and during an intermittent fatiguing contraction at 1-min intervals and task …

Recovery From Supraspinal Fatigue Is Slowed In Old Adults After Fatiguing Maximal Isometric Contractions, Sandra K. Hunter, Gabrielle Todd, Jane E. Butler, Simon C. Gandevia, Janet L. Taylor

Exercise Science Faculty Research and Publications

This study compared the contribution of supraspinal fatigue to muscle fatigue in old and young adults. Transcranial magnetic stimulation (TMS) of motor cortex was used to assess voluntary activation during maximal voluntary contractions (MVCs) of elbow flexor muscles in 17 young adults (25.5 ± 3.6 yr; mean ± SD) and 7 old adults (73.0 ± 3.3 yr). Subjects performed a fatigue task involving six sustained MVCs (22-s duration, separated by 10 s). Young adults exhibited greater reductions in maximal voluntary torque (67 ± 15% of baseline) than the old (37 ± 6%; P < 0.001). Increments in torque (superimposed twitch) generated by TMS during sustained MVCs increased for the young and old(P < 0.001) but were larger for the old adults at the start of the sustained contractions and during recovery (P < 0.05). Voluntary activation was less for the old adults at the start of some sustained contractions and during recovery(P = 0.02). Motor-evoked potential …

Time To Task Failure And Muscle Activation Vary With Load Type For A Submaximal Fatiguing Contraction With The Lower Leg, Sandra K. Hunter, Tejin Yoon, Joseph Farinella, Erin E. Griffith, Alexander V. Ng

Exercise Science Faculty Research and Publications

The purpose was to compare the time to failure and muscle activation patterns for a sustained isometric submaximal contraction with the dorsiflexor muscles when the foot was restrained to a force transducer (force task) compared with supporting an equivalent inertial load and unrestrained (position task). Fifteen men and women (mean ± SD; 21.1 ± 1.4 yr) performed the force and position tasks at 20% maximal voluntary contraction force until task failure. Maximal voluntary contraction force performed before the force and position tasks was similar (333 ± 71 vs. 334 ± 65 N), but the time to task failure was briefer …

Mechanisms Of Fatigue Differ After Low- And High-Force Fatiguing Contractions In Men And Women, Tejin Yoon, Bonnie A. Schlinder-Delap, Erin E. Griffith, Sandra K. Hunter

Exercise Science Faculty Research and Publications

The magnitude of failure in voluntary drive after fatiguing contractions of different intensities in men and women is not known. The purpose of this study was to compare the time to task failure and voluntary activation of men and women for a sustained isometric contraction performed at a low and high intensity with the elbow flexor muscles. Nine men and nine women sustained an isometric contraction at 20% and 80% of maximal voluntary contraction (MVC) force until task failure during separate sessions. The men had a shorter time to failure than women for the 20% but not the 80% MVC …

Bactericidal And Cytotoxic Effects Of Chloramine-T On Wound Pathogens And Human Fibroblasts In Vitro, Luther C. Kloth, Joseph E. Berman, Linda Jean Laatsch-Lybeck, Phyllis A. Kirchner

Physical Therapy Faculty Research and Publications

OBJECTIVES: To evaluate cytotoxicity and bactericidal effects of chloramine-T.

METHODS: In vitro study of various concentrations and exposure times to preparations containing human fibroblasts or 1.5 x 10⁸ colony forming units per milliliter (CFU/mL) of 3 gram-positive bacteria-Staphylococcus aureus, methicillin-resistant S aureus, and vancomycin-resistant Enterococcus faecalis-and 2 gram-negative bacteria-Escherichia coli and Pseudomonas aeruginosa-with and without fetal bovine serum present.

MAIN OUTCOME MEASURES: Percentage reduction of bacterial growth and percentage of viable fibroblasts 48 hours after exposure.

RESULTS: All gram-positive growth was reduced by 95% to 100%, regardless of dose, with or without serum. …

Co-Localization Of P-Creb And P-Nr1 In Spinothalamic Neurons In A Chronic Muscle Pain Model, Marie K. Hoeger Bement, Kathleen A. Sluka

Physical Therapy Faculty Research and Publications

Activation of the cAMP pathway is an important mediator of chronic muscle pain. This study examined phosphorylation of the transcription factor cAMP-response-element-binding protein (p-CREB) and the NR1 subunit of the NMDA receptor (p-NR1) in the spinal cord. Bilateral mechanical hyperalgesia of the paw was induced by administering two injections of acidic saline, 5 days apart, into the gastrocnemius muscle of male Sprague–Dawley rats. The proportion of spinothalamic neurons that expressed p-NR1 or p-CREB did not change in the dorsal horn 24 h after the second intramuscular acid injection compared with animals that received pH 7.2 injections. This lack of change …

Antibacterial Activity Of Positive And Negative Polarity Low-Voltage Pulsed Current (Lvpc) On Six Typical Gram-Positive And Gram-Negative Bacterial Pathogens Of Chronic Wounds, Georg Daeschlein, Ojan Assadian, Luther C. Kloth, Christina Meinl, Frank Ney, Axel Kramer

Physical Therapy Faculty Research and Publications

The positive effect of electrical stimulation (ES) on wound healing has been shown in vitro and in vivo. On the basis of increased blood flow, protein denaturation, and stimulation of cellular defense, an antibacterial effect of ES is to be expected. Although the antibacterial effect of ES already has been demonstrated in vitro, little attention has been paid to the direct antibacterial effect of changing polarity of the applied current. The aim of this study was to investigate the antibacterial effect of positive and negative monophasic low-voltage pulsed current on typical Gram-positive and Gram-negative pathogens of chronic wounds. Using the …

Supraspinal Fatigue Does Not Explain The Sex Difference In Muscle Fatigue Of Maximal Contractions, Sandra K. Hunter, Jane E. Butler, Gabrielle Todd, Simon C. Gandevia, Janet L. Taylor

Exercise Science Faculty Research and Publications

Young women are less fatigable than young men for maximal and submaximal contractions, but the contribution of supraspinal fatigue to the sex difference is not known. This study used cortical stimulation to compare the magnitude of supraspinal fatigue during sustained isometric maximal voluntary contractions (MVCs) performed with the elbow flexor muscles of young men and women. Eight women (25.6 ± 3.6 yr, mean ± SD) and 9 men (25.4 ± 3.8 yr) performed six sustained MVCs (22-s duration each, separated by 10 s). Before the fatiguing contractions, the men were stronger than the women (75.9 ± 9.2 vs. 42.7 ± …

Active Hyperemia And Vascular Conductance Differ Between Men And Women For An Isometric Fatiguing Contraction, Sandra K. Hunter, Jennie M. Schletty, Kristine M. Schlachter, Erin E. Griffith, Aaron J. Polichnowski, Alexander V. Ng

Exercise Science Faculty Research and Publications

To understand the role of muscle perfusion in the sex differences of muscle fatigue, we compared the time to task failure, postcontraction (active) hyperemia, and vascular conductance for an isometric fatiguing contraction performed by young men and women with the handgrip muscles at 20% of maximal voluntary contraction (MVC) force. In study 1, the men (n = 16) were stronger than the women (n = 18), and study 2, the men (n = 7) and women (n = 7) were matched for strength. Isometric contractions were sustained during two sessions: 1) until the target …

Effects Of Sprint Training On Extrarenal Potassium Regulation With Intense Exercise In Type 1 Diabetes, Alison R. Harmer, Patricia A. Ruell, Michael J. Mckenna, Donald J. Chisholm, Sandra K. Hunter, Jeanette M. Thom, Norman R. Morris, Jeff R. Flack

Exercise Science Faculty Research and Publications

Effects of sprint training on plasma K⁺ concentration ([K⁺]) regulation during intense exercise and on muscle Na⁺-K⁺-ATPase were investigated in subjects with Type 1 diabetes mellitus (T1D) under real-life conditions and in nondiabetic subjects(CON). Eight subjects with T1D and seven CON undertook 7 wk of sprint cycling training. Before training, subjects cycled to exhaustion at 130% peak O₂ uptake. After training, identical work was performed. Arterialized venous blood was drawn at rest, during exercise, and at recovery and analyzed for plasma glucose, [K⁺], Na⁺ concentration ([Na⁺]), catecholamines, …

Effect Of Keyswitch Design Of Desktop And Notebook Keyboards Related To Key Stiffness And Typing Force, Marcia J. Bufton, Richard W. Marklin, Mark L. Nagurka, Guy G. Simoneau

Mechanical Engineering Faculty Research and Publications

This study aimed to compare and analyse rubber-dome desktop, spring column desktop and notebook keyboards in terms of key stiffness and fingertip typing force. The spring-column keyboard resulted in the highest mean peak contact force (0.86N), followed by the rubber dome desktop (0.68N) and the notebook (0.59N). All these differences were statistically significant. Likewise, the spring-column keyboard registered the highest fingertip typing force and the notebook keyboard the lowest. A comparison of forces showed the notebook (rubber dome) keyboard had the highest fingertip-to-peak contact force ratio (overstrike force), and the spring-column generated the least excess force (as a ratio of …

Wound Debridement With 25 Khz Ultrasound, Margaret Mccarty Stanisic, Barbara Provo, David L. Larson, Luther C. Kloth

Physical Therapy Faculty Research and Publications

Several methods of wound debridement are described in the literature and are available to health care providers who specialize in wound management. Methods include the use of sharp surgical instruments; mechanical methods, such as whirlpool and pulsed lavage with suction; proteolytic and collagenolytic enzymes; autolysis; and sterile fly larvae (maggots). The use of surgical debridement is generally considered the most efficient method when performed by a skilled physician, who may in one session use his or her discretion to excise some viable tissue along with necrotic tissue in the wound. Sharp debridement performed in a clinical setting is a less …

Variability Of Motor Unit Discharge And Force Fluctuations Across A Range Of Muscle Forces In Older Adults, Brian L. Tracy, Katrina S. Maluf, Jennifer L. Stephenson, Sandra K. Hunter

Exercise Science Faculty Research and Publications

Variability of motor unit discharge is a likely contributor to the greater force fluctuations observed in old adults at low muscle forces. We sought to determine whether the variability of motor unit discharge rate underlies the fluctuations in force during steady contractions across a range of forces in young (n = 11) and old (n = 14) adults. The coefficient of variation (CV) for discharge rate and force were measured during a force-matching task as the first dorsal interosseous muscle performed isometric contractions. The recruitment thresholds of the 78 motor units ranged from 0.04% to 34% of maximal …

Muscle Endurance Is Greater For Old Men Compared With Strength-Matched Young Men, Sandra K. Hunter, Ashley Critchlow, Roger M. Enoka

Exercise Science Faculty Research and Publications

The purpose was to compare the time to task failure for a sustained isometric contraction performed at a submaximal intensity with the elbow flexor muscles by young and old men who were matched for strength. Eight young men (18–31 yr) and eight old men (67–76 yr) sustained an isometric contraction at 20% of maximal voluntary contraction (MVC) torque until the target torque could no longer be achieved for at least 5 s. The maximal torque exerted at the wrist was similar for the young and old men before the fatiguing task (65.9 ± 8.0 vs. 65.4 ± 8.7 N·m; P …

Time To Task Failure Differs With Load Type When Old Adults Perform A Submaximal Fatiguing Contraction, Sandra K. Hunter, Ludovic Rochette, Ashley Critchlow, Roger M. Enoka

Exercise Science Faculty Research and Publications

Young adults exhibit a longer time to task failure when performing a submaximal isometric contraction by pushing against a force transducer (force task) than when supporting an equivalent inertial load (position task). The purpose of this study was to compare the time to failure for old adults when they performed a force task and a position task with the elbow flexor muscles. Eighteen old adults (72 ± 4 years) performed the force and position tasks at 20% maximal voluntary contraction (MVC) force until task failure. The time to task failure was briefer for the position task (10.6 ± 6.1 min) …

Influence Of Aging On Sex Differences In Muscle Fatigability, Sandra K. Hunter, Ashley Critchlow, Roger M. Enoka

Exercise Science Faculty Research and Publications

The purpose of this study was to compare time to task failure for a sustained isometric contraction performed at a submaximal intensity with elbow flexor muscles by young and old men and women. Twenty-seven young (14 men and 13 women, 18–35 yr) and 18 old (10 men and 8 women, 65–80 yr) adults sustained an isometric contraction at 20% of maximal voluntary contraction torque until target torque could no longer be achieved for ≥5 s. Young adults were stronger than old adults (66.8 ± 17.9 vs. 47.7 ± 18.1 N·m, P < 0.05), and men were stronger than women (69.8 ± 17.9 vs. 47.1 ± 15.3 N·m, P < 0.05), with no interaction between age and sex (P > 0.05). Time to task failure was longer …

Men Are More Fatigable Than Strength-Matched Women When Performing Intermittent Submaximal Contractions, Sandra K. Hunter, Ashley Critchlow, In-Sik Shin, Roger M. Enoka

Exercise Science Faculty Research and Publications

The purpose of this study was to compare the time to task failure for a series of intermittent submaximal contractions performed with the elbow flexor muscles by men and women who were matched for strength (n = 20, 18–34 yr). The fatigue task comprised isometric contractions at 50% of maximal voluntary contraction (MVC) torque (6-s contraction, 4-s rest). The MVC torque was similar for the men and women [64.8 ± 9.2 (SD) vs. 62.2 ± 7.9 N·m; P > 0.05]. However, the time to task failure was longer for the women (1,408 ± 1,133 vs. 513 ± 194 s; P …

Management Of Postsurgical Hyperhidrosis With Direct Current And Tap Water, Bernadette T. Gillick, Luther C. Kloth, Andrew John Starsky, Laura Cincinelli-Walker

Physical Therapy Faculty Research and Publications

Background and Purpose. Excessive sweating, known as hyperhidrosis, involves the eccrine sweat glands of the axillae, soles, palms, and/or forehead. The use of iontophoresis to reduce or eliminate excessive sweating has been described since 1952. The purpose of this case report is to describe the use of tap water galvanism (TWG) using direct current (DC) with a patient who had postsurgical hyperhidrosis. Case Description. The patient was a 36-year-old male electrician with traumatic phalangeal amputation and postsurgical development of hyperhidrosis. Tap water galvanism was administered using a DC generator, 2 to 3 times per week for 10 treatments. The patient's …

Fatigability Of The Elbow Flexor Muscles For A Sustained Submaximal Contraction Is Similar In Men And Women Matched For Strength, Sandra K. Hunter, Ashley Critchlow, In-Sik Shin, Roger M. Enoka

Exercise Science Faculty Research and Publications

The purpose of this study was to compare the time to task failure for a submaximal fatiguing contraction sustained with the elbow flexor muscles by men and women who were matched for strength (n = 20, 18-35 yr). The maximal torque exerted at the wrist was similar for the men and women [64.5 ± 8.7 (SD) vs. 64.5 ± 8.3 N·m; P > 0.05], which meant that the average torque exerted during the fatiguing contraction [20% of maximum voluntary contraction (MVC)] was similar for the two sexes. The time to task failure was similar for these strength-matched men and women …

Muscle Fatigue And The Mechanisms For Task Failure, Sandra K. Hunter, Jacques Duchateau, Roger M. Enoka

Exercise Science Faculty Research and Publications

An alternative approach in the study of muscle fatigue is to address the question, “What causes task failure during a fatiguing contraction?” This approach is described by considering how variation in the type of load supported and contraction intensity influence both the time to task failure and the centrally mediated adjustments in reflex activity and motor unit behavior

Effect Of Computer Keyboard Slope On Wrist Position And Forearm Electromyography Of Typists Without Musculoskeletal Disorders, Guy G. Simoneau, Richard W. Marklin, Joseph E. Berman

Physical Therapy Faculty Research and Publications

Positioning a computer keyboard with a downward slope reduces wrist extension needed to use the keyboard and has been shown to decrease pressure in the carpal tunnel. However, whether a downward slope of the keyboard reduces electromyographic (EMG) activity of the forearm muscles, in particular the wrist extensors, is not known. Subjects and Methods. Sixteen experienced typists participated in this study and typed on a conventional keyboard that was placed on slopes. Electromyographic activity of the extensor carpi ulnaris (ECU), flexor carpi ulnaris (FCU), and flexor carpi radialis (FCR) muscles was measured with surface electrodes, while the extension and ulnar …

A Randomized Controlled Clinical Trial To Evaluate The Effects Of Noncontact Normothermic Wound Therapy On Chronic Full-Thickness Pressure Ulcers, Luther C. Kloth, Joseph E. Berman, Marilyn Nett, Paula E. Papanek, Sonia Dumit-Minkel

Physical Therapy Faculty Research and Publications

OBJECTIVE: To determine the effect of noncontact normothermic wound therapy (NNWT) versus standard wound care on chronic full-thickness pressure ulcers.

DESIGN: Prospective, randomized, controlled trial

SETTING: Veterans administration medical center and 7 long-term-care facilities

PATIENTS: 40 inpatients with 43 Stage III and IV pressure ulcers

INTERVENTIONS: A sterile noncontact wound dressing was applied to 21 wounds for 24 hours per day, 7 days per week. Each day after the wound was irrigated and the noncontact dressing was changed, a heating element in the dressing was activated for 3 1-hour periods for 12 weeks or until wound closure. Twenty-two control wounds …

Ventilatory Phenotypes Among Four Strains Of Adult Rats., Matthew Hodges, Hubert Forster, Paula E. Papanek, Melinda R. Dwinell, Genevieve E. Hogan

Exercise Science Faculty Research and Publications

Our purpose in this study was to identify different ventilatory phenotypes among four different strains of rats. We examined 114 rats from three in-house, inbred strains and one outbred strain: Brown Norway (BN;n = 26), Dahl salt-sensitive (n = 24), Fawn-hooded Hypertensive (FHH: n = 27), and outbred Sprague-Dawley rats (SD; n = 37). We measured eupneic (room air) breathing and the ventilatory responses to hypoxia (12% O₂-88% N₂), hypercapnia (7% CO₂), and two levels of submaximal exercise. Primary strain differences were between BN and the other strains. BN rats had a …

5 Questions–And Answers–About Negative Pressure Wound Therapy, Luther C. Kloth

Physical Therapy Faculty Research and Publications

No abstract provided.

Angiotensin Ii And Vegf Are Involved In Angiogenesis Induced By Short-Term Exercise Training, Sandra L. Amaral, Paula E. Papanek, Andrew S. Greene

Exercise Science Faculty Research and Publications

Results from our laboratory have suggested a pathway involving angiotensin II type 1 (AT₁) receptors and vascular endothelial growth factor (VEGF) in angiogenesis induced by electrical stimulation. The present study investigated if similar mechanisms underlie the angiogenesis induced by short-term exercise training. Seven days before training and throughout the training period, male Sprague-Dawley rats received either captopril or losartan in their drinking water. Rats underwent a 3-day treadmill training protocol. The tibialis anterior and gastrocnemius muscles were harvested under anesthesia and lightly fixed in formalin (vessel density) or frozen in liquid nitrogen (VEGF expression). In controls, treadmill training …

5 Questions–And Answers–About Electrical Stimulation, Luther C. Kloth

Physical Therapy Faculty Research and Publications

No abstract provided.

Effect Of Setup Configurations Of Split Computer Keyboards On Wrist Angle, Richard W. Marklin, Guy G. Simoneau

Physical Therapy Faculty Research and Publications

Alternative computer keyboards whose halves can be slanted toward each other can reduce a risk factor (ulnar deviation) for work-related musculoskeletal disorders (WMSDs) affecting the upper limbs. Two questions that computer keyboard operators face when using keyboards that can be separated into halves (split keyboards) are: (1) At what angle should the keyboard halves be opened? and (2) At what distance apart should the keyboard halves be placed? The objective of this study was to investigate the effects of the opening angle and separation distance between halves of a split keyboard on wrist ulnar deviation and typing efficiency. Methods. Eleven …

Walker-Assisted Gait In Rehabilitation: A Study Of Biomechanics And Instrumentation, Rebecca Ann Bachschmidt, Gerald F. Harris, Guy G. Simoneau

Physical Therapy Faculty Research and Publications

While walkers are commonly prescribed to improve patient stability and ambulatory ability, quantitative study of the biomechanical and functional requirements for effective walker use is limited. To date no one has addressed the changes in upper extremity kinetics that occur with the use of a standard walker, which was the objective of this study. A strain gauge-based walker instrumentation system was developed for the six degree-of-freedom measurement of resultant subject hand loads. The walker dynamometer was integrated with an upper extremity biomechanical model. Preliminary system data were collected for seven healthy, right-handed young adults following informed consent. Bilateral upper extremity …

Whole Body Momentum During Gait: A Preliminary Study Of Non-Fallers And Frequent Fallers, Guy G. Simoneau, David E. Krebs

Physical Therapy Faculty Research and Publications

The importance of momentum in compensating for elderly individua ls ' strength deficits to achieve activities of daily living. such as rising from a chair ha.!o been demonstrated in earlier studies. Here we present a case control study of three healthy "non-fallers" and two "frequent fallers," All 5 elders were community-living and were tested in the gai l laboratory. A four-camera Selspot system was used to obtain whole-body momentum from an 11-segment kinematic model. Ground reaction forces and kinematics were used 10 calculate lower extremity join! moments. With the exception of the whole-body's angular momentum about the vertical axis, linear …

Effects Of Electrical Stimulation On Wound Closure In Mice With Experimental Diabetes Mellitus, Habiba A. Thawer, Pamela E. Houghton, Luther Kloth, Anna Butryn

Physical Therapy Faculty Research and Publications

The purpose of the present study was to examine the effect of electrical stimulation (ES) on the closure of full-thickness excisional wounds in mice with type-1 experimental diabetes mellitus (DM). Alloxon monohydrate (100mg/kg) was used to induce experimental DM in mole CD-1 mice (n = 88). Full-thickness skin excisions (1cm²) in diabetic (urine glucose > 0) and non-diabetic (urine glucose = 0) mice were administered 1, 3, or 5 treatments of ES (200μs, 200 Hz) for 15 minutes, at 0 (sham), 5, 10, or 12.5 volts. Alloxon injection resulted in a positive urine glucose test in 48 mice yielding …