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Purpose: This study aimed to determine the effects of a 2-yr-long maintenance training (MT) exergaming and detraining (DT) on clinical-motor symptoms in subacute ischemic patients with stroke (PwST). The hypothesis was that MT motor rehabilitation program would further increase the effects of the initial rehabilitation., Methods: After high-intensity and high-frequency exergaming twice or once a day, 5 times per week for 5 wk (EX2: 50 sessions; EX1: 25 sessions, results reported previously), 558 PwST were randomized to EX2-MT, EX2-DT, EX1-MT, and EX1-DT. MT exergaming consisted of once a day, 3 times per week for 2 yr, and DT did not train. Outcomes were measured at 6, 12, 18, and 24 months. The data were analyzed using longitudinal linear mixed-effects models and general linear hypotheses testing., Results: Modified Rankin Score (primary outcome), body mass, Mini-Mental State Examination score, Beck Depression Inventory, measures of quality of life, Berg Balance Scale, 6-min walk test, and four measures of center of pressure path tended to retain the initial rehabilitation-induced gains in the MT patients in selected outcomes (especially walking capacity). The scores tended to mildly worsen after DT, partially supporting the hypothesis., Conclusions: MT successfully maintained, but only in selected variables did it further increase the initial exergaming rehabilitation-induced robust improvements. DT modestly reduced the initial exergaming rehabilitation-induced improvements. MT programs might be needed after initial stroke rehabilitation to reduce subsequent losses of quality of life and further improve clinical-motor symptoms., (Copyright © 2022 by the American College of Sports Medicine.)

Many adults older than 60 yr experience mobility limitations. Although physical exercise improves older adults' mobility, differences in baseline mobility produce large variations in individual responses to interventions, and these responses could further vary by the type and dose of exercise. Here, we propose an exercise prescription model for older adults based on their current mobility status.

Introduction: The ability to adapt dynamic balance to perturbations during gait deteriorates with age. To prevent age-related decline in adaptive control of dynamic balance, we must first understand how adaptive control of dynamic balance changes across the adult lifespan. We examined how adaptive control of the margin of stability (MoS) changes across the lifespan during perturbed and unperturbed walking on the split-belt treadmill., Methods: Seventy-five healthy adults (age range, 18-80 yr) walked on an instrumented split-belt treadmill with and without split-belts. Linear regression analyses were performed for the mediolateral (ML) and anteroposterior (AP) MoS, step length, single support time, step width, double support time, and cadence during unperturbed and perturbed walking (split-belt perturbation), with age as predictor., Results: Age did not significantly affect dynamic balance during unperturbed walking. However, during perturbed walking, the ML MoS of the leg on the slow belt increased across the lifespan due to a decrease in bilateral single support time. The AP MoS did not change with aging despite a decrease in step length. Double support time decreased and cadence increased across the lifespan when adapting to split-belt walking. Age did not affect step width., Conclusions: Aging affects the adaptive control of dynamic balance during perturbed but not unperturbed treadmill walking with controlled walking speed. The ML MoS increased across the lifespan, whereas bilateral single support times decreased. The lack of aging effects on unperturbed walking suggests that participants' balance should be challenged to assess aging effects during gait. The decrease in double support time and increase in cadence suggests that older adults use the increased cadence as a balance control strategy during challenging locomotor tasks.

Introduction: Different therapies can improve clinical and motor symptoms of multiple sclerosis (MS) similarly, but studies comparing the effects of different exercise therapies on clinical and motor outcomes are scant. We compared the effects of exergaming (EXE), balance (BAL), cycling (CYC), proprioceptive neuromuscular facilitation (PNF), and a standard care wait-listed control group (CON) on clinical and motor symptoms and quality of life (QoL) in people with MS (PwMS)., Methods: PwMS (n = 68, 90% female; age, 47.0 yr; Expanded Disability Status Scale score 5-6) were randomized into five groups. Before and after the interventions (five times a week for 5 wk), PwMS were tested for MS-related clinical and motor symptoms (Multiple Sclerosis Impact Scale-29 (MSIS-29), primary outcome), QoL (EuroQol Five Dimensions Questionnaire), symptoms of depression, gait and balance ability (Tinetti Assessment Tool), static and dynamic balance and fall risk (Berg Balance Scale), walking capacity (6-min walk test), and standing posturography on a force platform., Results: EXE, BAL, and CYC improved the MSIS-29 scores similarly. EXE and CYC improved QoL and walking capacity similarly but more than BAL. Only EXE improved gait and balance scores (Tinetti Assessment Tool). EXE and BAL improved fall risk and standing balance similarly but more than CYC. PNF and CON revealed no changes. The EuroQol Five Dimensions Questionnaire moderated the exercise effects on the MSIS-29 scores only in EXE. Changes in QoL and changes in the MSIS-29 scores correlated (R = 0.73) only in EXE., Conclusion: In conclusion, BAL and CYC but EXE in particular, but not PNF, can improve clinical and motor symptoms and QoL in PwMS (Expanded Disability Status Scale score 5 to 6), expanding the evidence-based exercise options to reduce mobility limitations in PwMS.

Introduction/purpose: Little is known about the comparative effectiveness of exercise programs, especially when delivered at a high intensity, in mobility-limited older adults. We compared the effects of 25 sessions of high-intensity agility exergaming (EXE) and stationary cycling (CYC) at the same cardiovascular load on measured and perceived mobility limitations, balance, and health-related quality of life in mobility-limited older adults., Methods: Randomized to EXE (n = 28) and CYC (n = 27), mobility-impaired older adults (age 70 yr) exercised five times per week for 5 wk at 80% of age-predicted maximal heart rate. Waitlisted controls did not exercise (n = 28)., Results: Groups did not differ at baseline in any outcomes (P > 0.05). The primary outcomes (The Short Form-36-Health Survey: EXE, 6.9%; effect size, 2.2; CYC, 5.5%, 1.94; Western Ontario and McMaster Universities Osteoarthritis Index: EXE, -27.2%, -3.83; CYC, -17.2, -2.90) improved similarly (P > 0.05). Secondary outcomes, including body mass (-3.7%), depression (-18%), and walking capacity (13.5%) also improved (P < 0.05) similarly after the two interventions. Activities of daily living, Berg Balance Score, BestTest scores, and Dynamic Gait Index improved more (P < 0.05) after EXE than CYC. Center of pressure of standing sway path improved in one of six tests only after EXE (P < 0.05). Postexercise cardiovascular response improved in EXE (P = 0.019). CON did not change in any outcomes (P > 0.05)., Conclusions: When matched for cardiovascular and perceived effort, two diverse high-intensity exercise programs improved health-related quality of life, perceived mobility limitation, and walking capacity similarly and balance outcomes more in mobility-limited older adults, expanding these older adults' evidence-based exercise options to reduce mobility limitations.

Introduction: Advanced age brings a distal-to-proximal redistribution of positive joint work during walking that is relevant to walking performance and economy. It is unclear whether negative joint work is similarly redistributed in old age. Negative work can affect positive work through elastic energy return in gait. We determined the effects of age, walking speed, and grade on positive and negative joint work in young and older adults., Methods: Bilateral ground reaction force and marker data were collected from healthy young (age = 22.5 yr, n = 18) and older (age = 76.0 yr, n = 22) adults walking on a split-belt instrumented treadmill at 1.1, 1.4, and 1.7 m·s at each of three grades (0%, 10%, and -10%). Subjects also performed maximal voluntary eccentric, isometric, and concentric contractions for the knee extensors (120°·s, 90°·s, and 0°·s) and plantarflexors (90°·s, 30°·s, and 0°·s)., Results: Compared with young adults, older adults exhibited a distal-to-proximal redistribution of positive leg joint work during level (P < 0.001) and uphill (P < 0.001) walking, with larger differences at faster walking speeds. However, the distribution of negative joint work was unaffected by age during level (P = 0.150) and downhill (P = 0.350) walking. Finally, the age-related loss of maximal voluntary knee extensor (P < 0.001) and plantarflexor (P = 0.001) strength was smaller during an eccentric contraction versus concentric contraction for the knee extensors (P < 0.001) but not for the plantarflexors (P = 0.320)., Conclusion: The distal-to-proximal redistribution of positive joint work during level and uphill walking is absent for negative joint work during level and downhill walking. Exercise prescription should focus on improving ankle muscle function while preserving knee muscle function in older adults trying to maintain their independence.

Introduction: Parkinson's disease (PD) is a progressive neurodegenerative condition and it is unclear if long-term nonpharmaceutical interventions can slow the progression of motor and nonmotor symptoms and lower drug dose., Methods: In a randomized trial, after an initial 3-wk-long, 15-session supervised high-intensity sensorimotor agility exercise (E) program designed to improve postural instability, the exercise+maintenance (E + M, n = 19) group continued to exercise three times per week for 2 yr, whereas E (n = 16), and the no exercise and no maintenance control (C, n = 20) continued habitual living. Eight outcomes were measured before and after the 3-wk initial exercise program and then at 3, 6, 9, 12, 18, and 24 months in all patients., Results: The group-time interactions (all P < 0.005) revealed robust and favorable effects of the initial 3-wk agility program on all six nonmotor (e.g., primary outcome Movement Disorder Society Unified Parkinson Disease Rating Scale, Motor Experiences of Daily Living, ~7 points; EuroQoL, ~9 points) and on each of the two motor outcomes (timed up and go test: ~6 s; posturography: up to 7 mm improvements in center of pressure path). E + M maintained but did not further improve the benefits produced by the initial 3-wk program. In E, the favorable effects of the 3-wk agility program lasted for 3 to 12 months. In C, patients declined steadily in all outcomes over 2 yr. By year 2, Leva-dopa equivalents increased by 99.4 mg·d (time main effect, P = 0.008)., Conclusions: A high-intensity sensorimotor agility program with but not without a 2-yr maintenance program slowed the progression of parkinsonian symptoms.

Introduction: Task difficulty affects the amount of interpretable information from a task, which is thought to interfere with motor learning. However, it is unclear whether task difficulty in itself is a stimulus for motor learning because the experimental evidence is mixed in support of the optimal challenge point framework that predicts one specific level of task difficulty to produce the greatest magnitude of motor learning., Purpose: We determined the effects of functional task difficulty on motor skill acquisition, retention, and transfer., Methods: Healthy young participants (N = 36) learned a mirror star-tracing task at a low, medium, or hard difficulty level defined by the bandwidth of the star. We measured skill acquisition, retention, and transfer to untrained difficulty levels, as well as the perceived mental workload during the task., Results: Task difficulty affected motor performance, but did not affect motor learning and transfer. For the groups that practiced the task at the medium and hard but not at the low difficulty level, initial skill level correlated with the magnitude of learning., Conclusions: The optimal challenge point framework does not capture the complex relationship between task difficulty and motor learning. Previously reported effects of task difficulty on the magnitude of motor learning are probably mediated by perceived mental workload. Task difficulty did not affect the magnitude of visuomotor skill learning but it affected how learning occurred. The data have implications on how athletes learn new motor skills and patients relearn injury-impaired motor skills during rehabilitation.

Introduction/purpose: Aging modifies neuromuscular activation of agonist and antagonist muscles during walking. Power training can evoke adaptations in neuromuscular activation that underlie gains in muscle strength and power but it is unknown if these adaptations transfer to dynamic tasks such as walking. We examined the effects of lower-extremity power training on neuromuscular activation during level gait in old adults., Methods: Twelve community-dwelling old adults (age ≥ 65 yr) completed a 10-wk lower-extremity power training program and 13 old adults completed a 10-wk control period. Before and after the interventions, we measured maximal isometric muscle strength and electromyographic (EMG) activation of the right knee flexor, knee extensor, and plantarflexor muscles on a dynamometer and we measured EMG amplitudes, activation onsets and offsets, and activation duration of the knee flexors, knee extensors, and plantarflexors during gait at habitual, fast, and standardized (1.25 ± 0.6 m·s) speeds., Results: Power training-induced increases in EMG amplitude (~41%; 0.47 ≤ d ≤ 1.47; P ≤ 0.05) explained 33% (P = 0.049) of increases in isometric muscle strength (~43%; 0.34 ≤ d ≤ 0.80; P ≤ 0.05). Power training-induced gains in plantarflexor activation during push-off (+11%; d = 0.38; P = 0.045) explained 57% (P = 0.004) of the gains in fast gait velocity (+4%; d = 0.31; P = 0.059). Furthermore, power training increased knee extensor activation (~18%; 0.26 ≤ d ≤ 0.29; P ≤ 0.05) and knee extensor coactivation during the main knee flexor burst (~24%, 0.26 ≤ d ≤ 0.44; P ≤ 0.05) at habitual and fast speed but these adaptations did not correlate with changes in gait velocity., Conclusions: Power training increased neuromuscular activation during isometric contractions and level gait in old adults. The power training-induced neuromuscular adaptations were associated with increases in isometric muscle strength and partly with increases in fast gait velocity.

Introduction: Slow gait predicts many adverse clinical outcomes in old adults, but the mechanisms of how power training can minimize the age-related loss of gait velocity is unclear. We examined the effects of 10 wk of lower extremity power training and detraining on healthy old adults' lower extremity muscle power and gait kinematics., Methods: As part of the Potsdam Gait Study, participants started with 10 wk of power training followed by 10 wk of detraining (n = 16), and participants started with a 10-wk control period followed by 10 wk of power training (n = 16). We measured gait kinematics (stride characteristic and joint kinematics) and isokinetic power of the ankle plantarflexor (20°·s, 40°·s, and 60°·s) and knee extensor and flexor (60°·s, 120°·s, and 180°·s) muscles at weeks 0, 10, and 20., Results: Power training improved isokinetic muscle power by ~30% (P ≤ 0.001) and fast (5.9%, P < 0.05) but not habitual gait velocity. Ankle plantarflexor velocity measured during gait at fast pace decreased by 7.9% (P < 0.05). The changes isokinetic muscle power and joint kinematics did not correlate with increases in fast gait velocity. The mechanisms that increased fast gait velocity involved higher cadence (r = 0.86, P ≤ 0.001) rather than longer strides (r = 0.49, P = 0.066). Detraining did not reverse the training-induced increases in muscle power and fast gait velocity., Conclusion: Because increases in muscle power and modifications in joint kinematics did not correlate with increases in fast gait velocity, kinematic mechanisms seem to play a minor role in improving healthy old adults' fast gait velocity after power training.

Purpose: Unilateral strength training strengthens not only the muscles on the trained side but also the homologous muscles on the untrained side; however, the magnitude of this interlimb cross-education is modest. We tested the hypothesis that heightened sensory feedback by mirror viewing the exercising hand would augment cross education by modulating neuronal excitability., Methods: Healthy adults were randomized into a mirror training group (MG, N = 11) and a no-mirror training group (NMG, N = 12) and performed 640 shortening muscle contractions of the right wrist flexors at 80% maximum voluntary contraction (MVC) during 15 sessions for 3 wk. Maximal strength and specific transcranial magnetic stimulation metrics of neuronal excitability, measured in the mirror and no-mirror setup at rest and during unilateral contractions at 60% MVC, were assessed before and after the strength intervention., Results: Trained wrist flexor MVC increased 72% across groups, whereas cross-education was higher for the MG (61%) than NMG (34%, P = 0.047). The MG showed a reduction (15%-16%) in the contralateral silent period duration measured from the contracting left-untrained flexor carpi radialis, whereas the NMG showed an increase (12%, P ≤ 0.030). Interhemispheric inhibition, measured from the trained to the untrained primary motor cortex, increased in the MG (11%) but decreased in the NMG (15%) when measured in the mirror setup at rest (P = 0.048). Other transcranial magnetic stimulation measures did not change., Conclusion: Viewing the exercising hand in a mirror can augment the cross-education effect. The use of a mirror in future studies can potentially accelerate functional recovery from unilateral impairment due to stroke or upper limb fracture.

Introduction: Chronic unimanual motor practice increases the motor output not only in the trained but also in the nonexercised homologous muscle in the opposite limb. We examined the hypothesis that adaptations in motor cortical excitability of the nontrained primary motor cortex (iM1) and in interhemispheric inhibition from the trained to the nontrained M1 mediate this interlimb cross education., Methods: Healthy, young volunteers (n=12) performed 1000 submaximal voluntary contractions (MVC) of the right first dorsal interosseus (FDI) at 80% MVC during 20 sessions., Results: Trained FDI's MVC increased 49.9%, and the untrained FDI's MVC increased 28.1%. Although corticospinal excitability in iM1, measured with transcranial magnetic stimulation (TMS) before and after every fifth session, increased 6% at rest, these changes, as those in intracortical inhibition and facilitation, did not correlate with cross education. When weak and strong TMS of iM1 were delivered on a background of a weak and strong muscle contraction, respectively, of the right FDI, excitability of iM1 increased dramatically after 20 sessions. Interhemispheric inhibition decreased 8.9% acutely within sessions and 30.9% chronically during 20 sessions and these chronic reductions progressively became more strongly associated with cross education. There were no changes in force or TMS measures in the trained group's left abductor minimi digiti and there were no changes in the nonexercising control group (n=8)., Conclusions: The findings provide the first evidence for plasticity of interhemispheric connections to mediate cross education produced by a simple motor task.

Age alters the control of voluntary movement. A frequently observed adaptation is the increased agonist and antagonist muscle coactivation. Here we examine the evidence for spinal circuits mediating this change in motor behavior and propose the hypothesis that cortical mechanisms also contribute to this age-associated change in muscle coactivation.

Excitotoxic lesions in the magnocellular nucleus basalis (MBN) lead to a significant damage of cholinergic neurons concomitant with increased amyloid precursor protein (APP) expression in the cerebral cortex. However, the sensitivity of non-cholinergic neurons to excitotoxicity, and changes of APP expression in the damaged MBN are still elusive. Hence, we performed multiple-labeling immunocytochemistry for choline-acetyltransferase (ChAT), neuron-specific nuclear protein (NeuN) and APP 4, 24, and 48 h after NMDA infusion in the MBN. Whereas all cholinergic neurons were immunoreactive for NeuN, this neuronal marker also labeled a population of ChAT-immunonegative non-cholinergic neurons. Both neuron populations exhibited a similar degree of sensitivity to NMDA excitotoxicity that became evident as early as 4 h post-lesion. Cholinergic MBN neurons showed abundant APP immunoreactivity (approximately 90%), while only a fraction (approximately 20-30%) of non-cholinergic neurons expressed the protein. Remarkably, cholinergic but not non-cholinergic neurons retained their APP immunoreactivity after NMDA infusion. In conclusion, cholinergic MBN neurons are not preferentially sensitive to short-term excitotoxicity, but are one of the major sources of APP in the basal forebrain.

Purpose: Sprinting, bouncing, and spontaneous landings are associated with a forefoot contact whereas walking, running, and jumping are associated with heel-toe foot placement. Because such foot placement strategies influence landing mechanics or the ensuing performance, the purpose of this work was to compare lower extremity kinematics and kinetics and muscle activation patterns between drop vertical jumps performed with heel-toe (HTL) and forefoot (FFL) landings., Methods: Ten healthy male university students performed two types of drop jump from a 0.4-m high box placed 1.0-m from the center of the force plate. They were instructed to either land first on the ball of the feet without the heels touching the ground during the subsequent vertical jump, i.e., forefoot landing jump (FFL), or to land on the heels followed by depression of the metatarsals, i.e., heel-toe landing jump (HTL). Three successfully performed trials per jump type were included in the analysis. The criteria for selection of the correct jumps was proper foot position at contact as judged from video records and the shape of force-time curve., Results: The first peak and second peak determined from the vertical force-time curves were 3.4 times greater and 1.4 times lower for HTL compared with those with FFL (P<0.05). In the flexion phase of HTL, the hip and knee joints contributed 40% and 45% to the total torque, whereas during FFL the greatest torque contributions were 37% for both the knee and ankle joints. During the extension phase, the greatest torque contributions to the total torque were 41% and 45% by the knee and ankle joints during HTL and 34% and 55% during FFL. During the flexion phase, power production was 20% greater (P<0.05) in HTL than in FFL, whereas during the extension phase power production was 40% greater in FFL than in HTL. In the flexion phase of HTL the hip and knee joints produced the greatest power, and during the extension phase the knee and ankle joints produced the greatest power. In contrast, during both the flexion and extension phases of FFL, the knee and ankle joints produced the greatest power. The EMG activity of gluteus, vastus lateralis, and plantar flexor muscles was similar between HTL and FFL in most cases except for the greater vastus lateralis EMG activity during precontact phase in HTL than in FFL and the greater gastrocnemius activity in FFL than in HTL., Conclusion: Foot placement strategy modifies the individual joint contributions to the total power during drop jumping.

The hypothesis was tested that the magnitude of cross education is greater following training with muscle lengthening than shortening. Changes in contralateral concentric, eccentric, and isometric strength and vastus lateralis and biceps femoris surface electromyographic (EMG) activity were analyzed in groups of young men who exercised the ipsilateral quadriceps with either eccentric (N = 7) or concentric (N = 8) contractions for 36 sessions over 12 wk. Control subjects (N = 6) did not train. Concentric training increased concentric strength 30% and isometric strength 22%, and eccentric training increased eccentric strength 77% and isometric strength 39% (all P < 0.05). Eccentric training improved eccentric strength three times more than the concentric training improved concentric strength (P < 0.05), and eccentric compared with concentric training improved isometric strength about 2 times more (P < 0.05). The eccentric group improved significantly from pre- to mid-training in eccentric and isometric strength (P < 0.05). The control group showed no significant changes (P < 0.05). Surface EMG activity of the vastus lateralis increased 2.2 times (pre- to mid-training), 2.8 (mid- to post-training) and 2.6 more (pre- to post-training) (P < 0.05) in the eccentric than concentric group. No significant changes in EMG activity occurred in the control group (P > 0.05). It was concluded that the greater cross education following training with muscle lengthening is most likely being mediated by both afferent and efferent mechanisms that allow previously sedentary subjects to achieve a greater activation of the untrained limb musculature.

We investigated the effects of 14 d of resistive exercise detraining on 12 power athletes. In comparing performances pre- to post-detraining, there were no significant (P > 0.05) changes in free weight bench press (-1.7%), parallel squat (-0.9%), isometric (-7%) and isokinetic concentric knee extension force (-2.3%), and vertical jumping (1.2%). In contrast, isokinetic eccentric knee extension force decreased in every subject (-12%, P < 0.05). Post-detraining, the changes in surface EMG activity of the vastus lateralis during isometric, and isokinetic eccentric and concentric knee extension were -8.4%, -10.1%, and -12.7%, respectively (all P > 0.05). No significant changes occurred in knee flexion forces or EMGs (P > 0.05). Percentages of muscle fiber types and the Type I fiber area remained unchanged, but Type II fiber area decreased significantly by -6.4% (P < 0.05). Levels of plasma growth hormone (58.3%), testosterone (19.2%), and the testosterone to cortisol ratio (67.6%) increased, whereas plasma cortisol (-21.5%) and creatine kinase enzyme levels (-82.3%) decreased (all P < 0.05). Short-term resistive exercise detraining may thus specifically affect eccentric strength or the size of the Type II muscle fibers, leaving other aspects of neuromuscular performance uninfluenced. Changes in the hormonal milieu during detraining may be conducive to an enhanced anabolic process, but such changes may not materialize at the tissue level in the absence of the overload training stimulus.

Competitive swimmers progressively reduce training volume or "taper" prior to an important competition in an effort to improve performance capabilities. The purpose of the current study was to determine the effects of taper upon factors associated with swim performance. Twelve intercollegiate swimmers were tested before and after taper in preparation for their season-ending meet. Power during a tethered sprint swim increased significantly (P < 0.05) by approximately 5% with taper. No significant changes occurred in distance per stroke, oxygen consumption, and post-exercise blood lactate level during a 182.9-m submaximal swim with taper. Five swimmers were additionally tested after shaving exposed body hair upon completion of taper. Swim power did not increase further with hair removal. In contrast, shaving significantly increased distance per stroke (P < 0.05) by approximately 5%. These data indicate that reduced training specifically improves swim power; however, removing exposed body hair after taper may additionally enhance performance capabilities by increasing distance per stroke.

Electromyostimulation (EMS) evoked responses of lower extremity muscles of sedentary or disabled subjects have been extensively studied to improve muscular strength and delay atrophy. However, it is not apparent whether EMS can serve a similar function in upper extremity muscles and in athletes. We compared the forces of maximal voluntary isometric contraction (MVC), percutaneous EMS-evoked tetanus, and EMS superimposed on MVC of the elbow flexors in six strength-trained and six untrained healthy men. Stimulation consisted of a 2.5-kHz alternating current sine wave modulated at 50 bursts.s-1 with a 50% duty cycle. Reliability of the criterion measures was assessed over 4 d and ranged from R = 0.746 to R = 0.948. Strength-trained men had 29% higher MVC than untrained controls (P less than 0.001). Untrained men tolerated 21.9 mA and trained men 31.3 mA of EMS current (P less than 0.021), yet tetanic forces were similar: 92.5 N vs 96.0 N (P greater than 0.196). These tetanic forces corresponded to 32% (untrained) and 24% (trained) of MVC (P less than 0.047). When EMS was superimposed on MVC, compared with MVC alone, force was significantly (P less than 0.048) lower by 10% (31 N, untrained) and 13% (55 N, trained). These data suggest that, independent of training status, percutaneous EMS reduces maximal voluntary elbow flexion forces and that tetanic forces may not be sufficiently high for purposes of muscular strength development or prevention of atrophy.