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Stuart Binder-Macleod, PT, PhD, FAPTA, the 51st Mary McMillan lecturer, is the Edward L. Ratledge Professor of Physical Therapy and associate vice president for clinical and translation research at the University of Delaware (UD). He served as the chair of UD's department of physical therapy for 16 years, and his research laboratory had more than 25 years of continuous National Institutes of Health funding, including major funding for projects involving the development and testing of treatment interventions for individuals demonstrating poststroke hemiparesis. A recipient of multiple honors from the American Physical Therapy Association (APTA) and its components, Binder-Macleod also served on the task force that created the American Council of Academic Physical Therapy, and he currently serves on the Board of Trustees of the Foundation for Physical Therapy Research. Keywords: Education: Faculty, Education: Physical Therapist Assistant Students, Education: Physical Therapist Students, Leadership, Mentoring, Professional Issues, What a Long Strange Trip It Has Been What an honor this is for me to present this 51st Mary McMillan Lecture as part of APTA's [American Physical Therapy Association's] [...]

Background. Recent research demonstrated that the symmetry of corticomotor drive with the paretic and nonparetic plantarflexor muscles was related to the biomechanical ankle moment strategy that people with chronic stroke [...]

Hyperlipidemia, also known as high blood cholesterol, is a cardiovascular health risk that affects more than one third of adults in the United States. Statins are commonly prescribed and successful lipid-lowering medications that reduce the risks associated with cardiovascular disease. The side effects most commonly associated with statin use involve muscle cramping, soreness, fatigue, weakness, and, in rare cases, rapid muscle breakdown that can lead to death. Often, these side effects can become apparent during or after strenuous bouts of exercise. Although the mechanisms by which statins affect muscle performance are not entirely understood, recent research has identified some common causative factors. As musculoskeletal and exercise specialists, physical therapists have a unique opportunity to identify adverse effects related to statin use. The purposes of this perspective article are: (1) to review the metabolism and mechanisms of actions of statins, (2) to discuss the effects of statins on skeletal muscle function, (3) to detail the clinical presentation of statin-induced myopathies, (4) to outline the testing used to diagnose statin-induced myopathies, and (5) to introduce a role for the physical therapist for the screening and detection of suspected statin-induced skeletal muscle myopathy., High blood cholesterol, or hyperlipidemia, is a common cardiovascular system problem. In the United States, 35.6% of adults have been told that they have hyperlipidemia. (1) Coronary artery disease is [...]

Background. Foot drop is a common gait impairment after stroke. Functional electrical stimulation (FES) of the ankle dorsiflexor muscles during the swing phase of gait can help correct foot drop. Compared with constant-frequency trains (CFTs), which typically are used during FES, novel stimulation patterns called variable-frequency trains (VFTs) have been shown to enhance isometric and nonisometric muscle performance. However, VFTs have never been used for FES during gait. Objective. The purpose of this study was to compare knee and ankle kinematics during the swing phase of gait when FES was delivered to the ankle dorsiflexor muscles using VFTs versus CFTs. Design. A repeated-measures design was used in this study. Participants. Thirteen individuals with hemiparesis following stroke (9 men, 4 women; age=46-72 years) participated in the study. Methods. Participants completed 20- to 40-second bouts of walking at their self-selected walking speeds. Three walking conditions were compared: walking without FES, walking with dorsiflexor muscle FES using CFTs, and walking with dorsiflexor FES using VFTs. Results. Functional electrical stimulation using both CFTs and VFTs improved ankle dorsiflexion angles during the swing phase of gait compared with walking without FES ([bar.X]±SE=-2.9°±1.2°). Greater ankle dorsiflexion in the swing phase was generated during walking with FES using VFFs ([bar.X]±SE=2.1 °+1.5°) versus CFTs ([bar.X]±SE=0.3±1.3°). Surprisingly, dorsiflexor FES resulted in reduced knee flexion during the swing phase and reduced ankle plantar flexion at toe-off. Conclusions. The findings suggest that novel FES systems capable of delivering VFTs during gait can produce enhanced correction of foot drop compared with traditional FES systems that deliver CFTs. The results also suggest that the timing of delivery of FES during gait is critical and merits further investigation., Stroke is a leading cause of long-term adult disability. (1) Regaining walking function is one of the primary concerns for individuals who experience stroke. (2) Even after rehabilitation, residual gait [...]

Background and Purpose During functional electrical stimulation (FES), clinicians typically increase stimulation intensity to offset fatigue and maintain functional levels of force production. However, recent studies have suggested that increasing [...]

Muscle fatigue has been defined as a temporary loss in force or torque-generating ability due to recent muscle contraction. (1) The mechanisms underlying muscle fatigue are numerous and may have [...]

Background and Purpose. Following spinal cord injury (SCI), paralyzed muscles undergo physiological changes that alter their force responses to electrical stimulation. The purpose of this study was to investigate the effects of SCI on the contractile properties and force-frequency relationship (FFR) of the paralyzed human quadriceps femoris muscle of adolescents and young adults. Subjects. Thirteen subjects (11 male, 2 female; age range=11-24 years) with motor complete SCIs and 13 matched control subjects (11 male, 2 female; age range=9-23 years) without SCI participated in the study. Methods. Both groups of subjects underwent the same testing protocol using similar equipment. Results. The paralyzed muscles of the subjects with SCI produced 62% of the peak twitch force and had a fatigue ratio that was 65% of that of the control subjects. The paralyzed muscles contracted 14% and 25% faster and relaxed 38% and 46% faster than the nonparalyzed muscles in nonfatigued and fatigued conditions, respectively. Compared with the control subjects, the subjects with SCI had twitch-to-tetanus ratios that were 84% and 127% greater in nonfatigued and fatigued conditions, respectively. Relative to the control subjects, the FFR of the subjects with SCI was shifted to the left in the fatigued condition. Relative to their respective nonfatigued conditions, the FFR of both groups of subjects shifted to the right with fatigue. Discussion and Conclusion. These findings may have important implications for designing stimulation strategies to reduce the rapid fatigue that limits the clinical efficacy of functional electrical stimulation. [Scott WB, Lee SCK, Johnston TE, et al. Contractile properties and the force-frequency relationship of the paralyzed human quadriceps femoris muscle. Phys Ther. 2006;86:788-799.] Key Words: Electrical stimulation, Muscle fatigue, Muscle performance, Muscle weakness, Muscular atrophy, Paralysis, Spinal cord injuries., Electrical stimulation of paralyzed skeletal muscle can be used to assist people with spinal cord injury (SCI) in performance of functional movements. (1) This therapeutic intervention is called functional electrical [...]

Key Words: Angiotensin-converting enzyme (ACE), Genetics, Rehabilitation. In the last 30 years, the field of genetics has proven to be a highly influential component of nearly all aspects of research [...]

Muscle fatigue is frequently defined as a temporary loss in force- or torque-generating ability because of recent, repetitive muscle contraction. (1) The development of this temporary loss of force is [...]

Human skeletal muscle is composed of a heterogenous collection of muscle fiber types. (1-3) This range of muscle fiber types allows for the wide variety of capabilities that human muscles [...]

Muscle fatigue can be defined as a decrease in the force-generating ability of a muscle that resulted from recent activity. Recent studies of muscle fatigue are reviewed that are relevant to two areas of interest to physical therapists clinical assessment of muscle fatigue and neuromuscular electrical stimulation, Volitional and electrical tests have been used to quantify muscle fatigue. Several variations on each type of test are discussed, as are the possible sites in which fatigue might occur The rate of fatigue during the therapeutic application of electrical stimulation of skeletal muscle is much greater than that seen during volitional contractions Factors contributing to this phenomenon are examined The unique requirements affecting bow stimulus variables can be manipulated to minimize muscle fatigue in three specific therapeutic uses of neuromuscular electrical stimulation are addressed. [Binder-Macleod SA, Snyder-Mackler L Muscle fatigue: clinical implications for fatigue assessment and neuromuscular electrical stimulation. Phys Ther. 1993;73.-902-910.] Key Words: Electrotherapy, electrical stimulation; Fatigue; Musculoskeletal system; Skeletal muscle., Fatigue has been described as a "failure to maintain the required or expected force" from a muscle following repeated activity of the muscle.[1] This is a functional definition of fatigue; [...]

The purpose of this study was to identify the changes in the force-frequency relationship (FFR) of the human quadriceps femoris muscle following electrically and voluntarily induced fatigue. Tweny nondisabled subjects each participated in one experimental session to test the effects of electrically induced fatigue on the FFR; 10 of these subjects participated in a second session in which voluntarily induced fatigue was produced. Fatigue was induced by having subjects perform repeated, 8-second, isometric contractions followed by 12-second rests until 50% of the initial force was produced. Markedly decreased forces were seen at all frequencies tested following fatigue. Low frequency fatigue was observed following both fatiguing protocols. The frequencies needed to produce near-maximum forces did not shift with fatigue. These results suggest that the most appropriate stimulation frequency to use when activating skeletal muscle depends on both the percentage of tetanic force desired and the fatigue state of the muscle. This study also provides the clinician with data on the FFR of healthy human quadriceps femoris muscle prior to fatigue. [Binder-Macleod SA, McDermond LR. Changes in the force-frequency relationship of the human quadriceps femoris muscle following electrically and voluntarily induced fatigue. Phys Ther. 1992;72:95-104.] Key Words: Electrotherapy, electrical stimulation; Fatigue; Force-frequency relationship; Low-frequency fatigue., Neuromuscular electrical stimulatioin (NMES) is used for a variety of purposes, including the transcutaneous stimulation of skeletal muscle to produce muscle strengthening (ie, increases in peak torque output). [1-7] The [...]

Electrical stimulation has been used for a long time as a way of increasing the force of muscle contraction in humans. Recent studies have addressed optimization of this technique. Muscle contraction force increases in proportion to increases in the frequency of electrical pulses. However, the higher the stimulation frequency, the faster the muscle fatigues. Therefore, adjustments in the pulse frequency are needed to maximize muscle force, while minimizing fatigue. Some studies have shown that rapid fatigue can be lessen by progressively reducing the pulse frequency over the treatment time; these studies generally have used continuous stimulation of muscles. In medical situations, intermittent, rather than continuous stimulation, is used to strengthen muscles. The effect of progressively reducing pulse frequency during intermittent stimulation of the quadriceps femoris muscle (muscle on the front of the thigh) was evaluated in 12 healthy young subjects aged 19 to 37 years; six subjects were men and six were women. After an initial similar decline, muscles stimulated by variable frequency fatigued less rapidly than those stimulated with constant frequency. This resulted in a greater total force output for the muscles stimulated with variable frequency. Further research is needed to optimize electrical stimulation protocols. Clinicians are encouraged to attempt to find the best protocol for each patient treated with this technique. (Consumer Summary produced by Reliance Medical Information, Inc.), The purpose of this study was to determine the effects of a reduction in the pulse frequency on the fatigue rate of human quadriceps femoris muscle during intermittent (8-second) contractions. Twelve healthy subjects each participated in two experimental sessions. Thirty cycles (cycle time: 8 seconds "on"/12 seconds "off") were applied during each session. During one session, a frequency of 60 pulses per second (pps) was used for all trains. During the other session, the subjects were stimulated with 60 pps for the first train. The stimulating frequency of each train was then progressively reduced, in 5-pps steps, for contractions 2, 3, 5, 8, 12, and 20. By the fifth contraction, the differences in average force produced by the 60-pps trains and the reduced-frequency trains were significant. The difference between the two conditions increased, with the variable-frequency protocol producing 46% more force than the constant-frequency protocol during the last contraction. These results showed that, compared with a constant pulse frequency, reducing the pulse frequency during a fatiguing contraction can markedly decrease the rate of force fatigue of skeletal muscle. This finding suggests that a variable-frequency protocol, similar to the one used in this study, may prove to be a more effective pattern of stimulation for activation of skeletal muscle than the traditionally used constant-frequency protocol. (Binder-Macleod SA, Guerin T. Preservation of force output through progressive reduction of stimulation frequency in human quadriceps femoris muscle. Phys Ther. 1990;70:619-625.] Key Words: Electrotherapy, electrical stimulation; Fatigue; Muscle performance, measurement; Musculoskeletal system., Neuromuscular electrical stimulation (NMES) has long been used by physical therapists to maintain or increase the force-generating capacity of human skeletal muscle. Recently, numerous studies [1-13] have been undertaken to [...]

Background and Purpose. Researchers studying central activation of muscles in elderly subjects ([is greater than or equal to] 65 years of age) have investigated activation in only the nonfatigued state. This study examined the ability of young and elderly people to activate their quadriceps femoris muscles voluntarily under both fatigued and nonfatigued conditions to determine the effect of central activation failure on age-related loss of force. Subjects and Methods. Twenty young subjects (11 men, 9 women; mean age=22.67 years, SD=4.14, range=18-32 years) and 17 elderly subjects (8 men, 9 women; mean age=71.5 years, SD=5.85, range=65-84 years) participated in this study. Subjects were seated on a dynamometer and stabilized. Central activation was quantified, based on the change in force produced by a 100-Hz, 12-pulse electrical train that was delivered during a 3- to 5-second isometric maximum voluntary contraction (MVC) of the quadriceps femoris muscle. Next, subjects performed 25 MVCs (a 5-second contraction with 2 seconds of rest) to fatigue the muscle. During the last MVC, central activation was measured again. Results. In the nonfatigued state, elderly subjects had lower central activation than younger subjects. In the fatigued state, this difference became larger. Discussion and Conclusion. Central activation of the quadriceps femoris muscle in elderly subjects was reduced in both the fatigued and nonfatigued states when compared with young subjects. Some part of age-related weakness, therefore, may be attributed to failure of central activation in both the fatigued and nonfatigued states. [Stackhouse SK, Stevens JE, Lee SCK, et al. Maximum voluntary activation in nonfatigued and fatigued muscle of young and elderly individuals. Phys Ther. 2001;81:1102-1109.] Key Words: Aging, Central activation, Maximum voluntary contraction, Skeletal muscle., Volitional activation of skeletal muscle requires proper functioning of both the central nervous system and peripheral neuromuscular pathways. The central nervous system processes involve the activation of the motor portions [...]