Agonist Muscle Groups Research Articles

Rehabilitation technique of proprioceptive neuromuscular facilitation applied to volleyball vertical jump: A randomized double blinded cross-over clinical trial

Objectivecompare the acute effect of lower limb stretching exercises with proprioceptive neuromuscular facilitation (PNF) on the antagonist and agonist muscle groups in the execution of a vertical jump (VJ). Methoda randomized, double-blind, crossover clinical trial was conducted involving 30 male volleyball athletes. Group A engaged in PNF on the antagonist muscles, while Group B applied the same method to the agonist muscles. Following a 48-h washout period, the interventions were swapped between the respective groups. Both groups underwent assessments averaging three countermovement vertical jumps (CVJ) with hands on hips and three VJ with arms free. Measurement was taken using the Encoder – Ergonauta I, with over 1500 jumps recorded. The participants were evaluated for their level of flexibility and VJ performance using the Jump Sigma Index application. Resultsan acute decrease in average performance was identified, amounting to 3.86 % for the CMJ with hands on hips and 3.06% for the CVJ with free hands, following PNF in the agonists. Conclusionthere was no statistical difference between the means before and after the intervention when PNF was applied to the antagonistic hamstring muscles. The CVJ modalities with hands on hips and with free hands presented statistically similar indices. The study suggests that there is no impediment to the implementation of warm-up or training protocols that involve stretching in the antagonistic muscles. Further research will be relevant to better clarify the relationship between the effects of stretching on antagonistic muscle groups and to formalize future protocols.

Effects of Running Velocity on Vertical Stiffness and Muscle Co-activations

The purpose of this study was to investigate the vertical stiffness and agonist-antagonist muscle co-activation according to running velocity. Eighteen runners asked to perform running on an instrumented treadmill (HP Cosmos, Germany) with a capacitance-based pressure platform at 40, 50, 60, 70, 80% of maximum velocities, 19 infrared cameras and surface electromyography were used to measure kinematics and muscle activation. Vertical stiffness increased significantly as running speed increased. On the other hand, co-activation decreased significantly as the running speed increased. We conclude that antagonist muscle groups decrease with increasing running speed and depend on agonist muscle group activity.

Luxación Voluntaria de Hombro en el Niño. Reporte de Dos Casos

BackgroundVoluntary dislocation of the glenohumeral joint represents the ability to spontaneously dislocate a shoulder in one or more directions. The theoretical cause is the ability to contract agonist muscle groups, and inhibiting or relaxing antagonistic muscles, thus determining the direction of the dislocation. The diagnosis is usually made in childhood or adolescence when the patient demonstrates a voluntary shoulder dislocation. Historically, this condition has been linked to psychological disorders or illness and typically responds poorly to surgical interventions. Treatment typically consists of conservative management including cognitive behavioral therapy or physical therapy. Prior prospective studies have demonstrated no advantage to surgical interventions over nonoperative treatments, and in some cases with associated increased morbidity. Case ReportBeing a rare condition, two cases of voluntary shoulder dislocation are reported. The first patient is a boy, 12-year-old with 2 years of voluntary bilateral posterior shoulder dislocations, with 17-year follow-up, the patient did well. The second case is an 8-year-old girl with voluntary posterior dislocation of the right shoulder who after three year follow up responded well to conservative treatment. DiscussionThe risk of developing osteoarthritic changes or the appearance of chondral lesions are major long-term concerns with this disease. Currently there is no specific treatment consensus and little evidence regarding the prognosis of this condition.Voluntary shoulder dislocation is a rare entity of unknown etiology. Patients report no history of trauma but is often associated with psychiatric conditions. Prospective studies have reported favorable results of nonoperative treatment during childhood.Evidence Level: IV

The Effect Of Concentric Prime Movers Vs. Synergist Muscle Contraction On Coactivation Ratios

PURPOSE: The purpose of this study was to examine the coactivation ratio of agonist to antagonist muscle groups with varying pre-exhaustion protocols, and to see if postactivation potentiation is influenced by pre-exhaustion. METHODS: Eight college age males and females were recruited for the study. Each participant visited the Human Performance Laboratory four times over the duration of the study. Subjects were monitored via EMG and randomly performed 1 set of 50 repetitions maximal voluntary knee extension, knee flexion, and knee extension/flexion at 60°•s-1 using an isokinetic machine on the dominant leg. They performed 1 set of 10 repetitions of modified Peterson step-up testing at pre-exercise, immediately post-exercise, and seven (7) min following exercise. RESULTS: The 50 repetitions of isokinetic knee extension, flexion, extension/flexion at 60•s-1resulted in a significant drop in peak torque in all groups (P<0.01). Pre-exhausting the agonist muscle group prior to Pearson step-up improved agonist skeletal muscle motor unit recruitment (P<0.05). Pre-exhausting the antagonist muscle group with flexion and combination prior to Pearson step-up did not have any effect on agonist skeletal muscle motor unit recruitment. Pre-exhausting the agonist muscle group down-regulated antagonist muscle activity. Coactivation improved only by fatiguing the agonist muscle group. Postactivation potentiation was only affected by fatiguing the agonist muscle group (P<0.05). CONCLUSIONS: We conclude that pre-exhausting the agonist muscle group might be beneficial for improving muscle activity in functional rehabilitation exercises and during the period of recovery. Given the small number of subjects in this study, additional research using larger subject groups and different fatiguing and post-activation protocols is warranted to support the use of pre-exhaustion techniques to improve activity/recruitment of atrophied muscle in physical therapy settings.

Central contributions to torque depression: an antagonist perspective.

Torque depression (TD) is the reduction in steady-state isometric torque following active muscle shortening when compared to an isometric reference contraction at the same muscle length and activation level. Central nervous system excitability differs in the TD state. While torque production about a joint is influenced by both agonist and antagonist muscle activation, investigations of corticospinal excitability have focused on agonist muscle groups. Hence, it is unknown how the TD state affects spinal and supraspinal excitability of an antagonist muscle. Eight participants (~ 24y, three female) performed 14 submaximal dorsiflexion contractions at the intensity needed to maintain a level of integrated electromyographic activity in the soleus equivalent to 15% of that recorded during a maximum plantar flexion contraction. The seven contractions of the TD protocol included a 2s isometric phase at an ankle angle of 140°, a 1s shortening phase at 40°/s, and a 7s isometric phase at an angle of 100°. The seven isometric reference contractions were performed at an ankle angle of 100° for 10s. Motor evoked potentials (MEPs), cervicomedullary motor evoked potentials (CMEPs), and maximal M-waves (Mmax) were recorded from the soleus in both conditions. In the TD compared to isometric reference state, a 13% reduction in dorsiflexor torque was accompanied by 10% lower spinal excitability (normalized CMEP amplitude; CMEP/Mmax), and 17% greater supraspinal excitability (normalized MEP amplitude; MEP/CMEP) for the soleus muscle. These findings demonstrate a neuromechanical coupling following active muscle shortening and indicate that the underlying mechanisms of TD influence antagonist activation during voluntary force production.

Non-uniformity in pre-insertional Achilles tendon is not influenced by changing knee angle during isometric contractions.

Achilles tendinopathy remains a prevalent condition among recreational and high-level athletes. Mechanical loading has become the gold standard in managing these injuries, but exercises are often generic and prescribed in a "one-size-fits-all" principle. The aim of this study was to evaluate the impact of knee angle changes and different levels of force production on the non-uniform behavior in the Achilles tendon during isometric contractions. It was hypothesized that a flexed knee position would lead to a more distinct non-uniform behavior, due to greater differential loading of soleus vs gastrocnemius, and that this effect would be attenuated by higher levels of force production. Contrary to the hypotheses, it was found that the non-uniform deformation, that is, superficial-to-deep variation in displacement with highest displacement in the deep layer, is consistently present, irrespective of the level of force production and knee angle (n=19; mean normalized displacement ratio 6.32%, 4.88%, and 4.09% with extended knee vs 5.47%, 2.56%, and 6.01% with flexed knee, at 25%, 50%, and 75% MVC, respectively; P>.05). From tendon perspective, aside from the influence on muscle behavior, this might question the mechanical rationale for a change in knee angle during eccentric heel drops. Additionally, despite reaching high levels of plantar flexion force, the relative contribution of the AT sometimes appears to be decreased, potentially due to compensatory actions by agonist muscle groups. These results are relevant for optimizing AT rehabilitation as the goal is to reach specific local tendon loading.

1. Impact of Surface Stability and Hand Separation on Activation of Agonist and Stabilizing Muscles During Push-Up Exercise

Stability is an important factor to consider when designing an exercise program as recent studies have suggested that there can be benefits to performing exercises on unstable surfaces compared to rigid ones. Furthermore, to increase strength of the agonist muscles, pectoralis major and triceps brachii, various hand positions can also be implemented to increase stress on these muscles during an exercise. Thus, our goal was to test the impact that surface stability and hand position can have on muscle activity of stabilizing and agonist muscles during a push-up exercise. Surface electrodes were attached to specific stabilizing and agonist muscles and electromyography (EMG) data was used to measure muscle activity. When compared to a rigid surface, a push up exercise performed on an unstable surface of a BOSU ball resulted in higher muscle activity for all the stabilizing muscles, while only the pectoralis major had an increase in activity for the agonist muscle group. In regards to hand position, a narrow hand spacing resulted in greater activation of all the stabilizing muscles and was able to specifically target the triceps brachii, while the use of wide hand spacing only isolated the pectoralis major. Hence an exercise program consisting of push-ups can target the stabilizing muscles further by using an unstable surface and a narrow hand position. In regards to the agonist muscles, the use of a specific surface and hand position can allow the user to target the agonist muscle they desire in a more efficient manner.

Acute effects of different foam rolling volumes in the interset rest period on maximum repetition performance.

Background:Foam rolling (FR) is a ubiquitous intervention utilised for the purpose of acutely increasing the range of motion without subsequent decreases in performance. Thus, it is commonly used during the periworkout period—that is, prior to, during, or after an athlete's workout.Objective:This study investigated how different FR durations applied to the quadriceps during the interset rest periods affects the numbers of repetitions in the knee extension exercise.Methods:Twenty-five females completed four sets of knee extensions with 10 repetitions of maximum load to concentric failure on four occasions. Between each set, a 4-minute rest interval was implemented in which participants either passively rested or performed FR for different durations (60 seconds, 90 seconds, and 120 seconds). The 95% confidence intervals revealed a dose-dependent relationship in which longer durations of FR resulted in fewer completed repetitions.Results:On average, the number of repetitions with PR was 13.8% greater than that in FR120, 8.6% greater than that in FR90, and 9.1% greater than that in FR60.Conclusion:For the purposes of performance and likely adaptation, interset FR seems to be detrimental to a person's ability to continually produce force, and should not be applied to the agonist muscle group between sets of knee extensions.

EFFECT OF A FOCAL MUSCLE VIBRATION ABOVE TRICEPS BRACHII MUSCLE ON UPPER LIMB SPASTICITY IN A PATIENT WITH A CHRONIC SPINAL CORD INJURY: A CASE REPORT

Aim: To estimate the effect of focal muscle vibration on the spasticity of antagonist muscle group (biceps brachii) and upper extremity muscles when we apply it to agonist muscle group (triceps brachii). Methodology: Our case study is a male patient who suffered from hemiparesis spastic due to spinal cord injury. He was initially evaluated using the modified ashworth scale (MAS). He received 10 sessions of 100 Hz focal muscle superficially to triceps brachii muscle, at the elbow joint. Major finding: We found that the spasticity for both the elbow joint and the non-vibrated wrist joint muscles has reduced. No effect was found on the tone of the shoulder joint. Conclusion: The applied focal muscle vibration on triceps brachii muscle can reduce the spasticity for both elbow and wrist joint muscles.

Measurements of Tennis Players’ Specific Forearm Muscle Force Imbalance to Assess the Potential Risk of Lateral Epicondylitis

Several studies suggested that lateral epicondylitis could potentially develop among tennis players presenting a muscle force imbalance, defined as a functional ratio weakness between agonist and antagonist muscles and/or a predominance of synergic muscles during the movement. Consequently, the measurement of muscle force capability and the assessment of imbalance between antagonist and agonist muscle groups could be useful in the context of clinical follow-up, ascertaining the subject's functional capabilities to return to tennis practice. The purpose of the present study was to develop a method to quantify subject's specific imbalance in forearm muscles to improve the knowledge about lateral epicondylitis. The study included a group of healthy male tennis players (n=11, no history of musculoskeletal problems) and specific tennismen profiles (recovered lateral epicondylitis (n=2), expert (n=1) and woman (n=1)). Maximal isometric net torques in both flexion and extension were measured at the metacarpophalangeal and wrist joints using an isokinetic ergometer. Tennis players’ specific fingers and wrist muscle force imbalance between agonistic and antagonistic prehension muscles were estimated using a two-step calculation procedure including (i) an EMG-calibration procedure in order to integrate the muscle coactivation in net joint torques calculation and; (ii) the calculation of the antagonist/agonist torque ratio from corrected joint torques. The results showed dissimilar muscle force imbalances between the healthy men group and recovered lateral epicondylitis players. The observed differences between healthy players and recovered lateral epicondylitis suggested that the proposed method of muscle force imbalance estimation may provide a useful assessment of functional recovery in lateral epicondylitis.

The Effects of Rest Interval Length Manipulation of the First Upper-Body Resistance Exercise in Sequence on Acute Performance of Subsequent Exercises in Men and Women

The purpose of the present study was to investigate the effects of manipulating rest interval (RI) length of the first upper-body exercise in sequence on subsequent resistance exercise performance. Twenty-two men and women with at least 1 year of resistance training experience performed resistance exercise protocols on 3 occasions in random order. Each protocol consisted of performing 4 barbell upper-body exercises in the same sequence (bench press, incline bench press, shoulder press, and bent-over row) for 3 sets of up to 10 repetitions with 75% of 1 repetition maximum. Bench press RIs were 1, 2, or 3 minutes, whereas other exercises were performed with a standard 2-minute rest interval. The number of repetitions completed, average power, and velocity for each set of each exercise were recorded. Gender differences were observed during the bench press and incline press as women performed significantly (p ≤ 0.05) more repetitions than men during all RIs. The magnitude of decline in velocity and power over 3 sets of the bench press and incline press was significantly higher in men than women. Manipulation of RI length during the bench press did not affect performance of the remaining exercises in men. However, significantly more repetitions were performed by women during the first set of the incline press using 3-minute rest interval than 1-minute rest interval. In men and women, performance of the incline press and shoulder press was compromised compared with baseline performances. Manipulation of RI length of the first exercise affected performance of only the first set of 1 subsequent exercise in women. All RIs led to comparable levels of fatigue in men, indicating that reductions in load are necessary for subsequent exercises performed in sequence that stress similar agonist muscle groups when 10 repetitions are desired.

Muscle Activation of the Elbow Flexor and Extensor Muscles During Self-Resistance Exercises

Muscle activation during self-resistance exercises was studied in 18 subjects performing (a) maximal unilateral isometric cocontractions of flexor and extensor muscles of the right elbow (UNI); (b) bilateral exercises consisting of maximal isometric extensions of the right elbow against the left elbow flexors (BiExt) and maximal isometric flexion of the right elbow against the left elbow extensors (BiFlex). Force production by the biceps brachii (BB), brachioradialis (BR), and triceps brachii (TB) during UNI, BiFlex, and BiExt were estimated by comparing the integrated surface electromyograms (iEMG) of BB, BR, and TB during UNI, BiExt, and BiFlex with the individual iEMG-force relationship determined from isometric contractions at 30, 60, and 100% maximal voluntary contraction during elbow flexion (MVCflex) or extension (MVCext) against a force transducer. During BiFlex for BB or BR and BiExt for TB, the values (mean ± SE) of BB-iEMG, BR-iEMG, and TB-iEMG were 74.0 ± 4.5, 76.6 ± 5.7, and 84.4 ± 4.5% iEMG at MVC (% iEMGmax). The forces were 86.0 ± 3.7% TB-Forcemax during BiExt, 74.1 ± 3.6% BB-Forcemax and 71.8 ± 4.0% BR-Forcemax during BiFlex. During UNI, BB-iEMG, BR-iEMG, and TB-iEMG were 59.9 ± 4.6, 53.4 ± 4.0, and 66.3 ± 4.7% iEMGmax, respectively. The forces during UNI (70.4 ± 4.0% TB-Forcemax, 60.4 ± 4.3% BB-Forcemax, and 49.2 ± 3.1% BR-Forcemax) were significantly lower than those during bilateral exercises. A 2-way analysis of variance (Muscle × Exercise) indicated that the effects of Muscle and Exercise upon % iEMGmax were significant (p < 0.05; p < 0.001, respectively). In conclusion, bilateral opposition exercises should be more effective in developing strength than cocontraction exercises, which correspond to a moderate activation level even for weak agonist muscle groups.

Effects of a Short-Term Resistance Program Using Elastic Bands Versus Weight Machines for Sedentary Middle-Aged Women

This study was designed to determine whether different effects on functional capacity and body composition were produced by using different devices (elastic bands (EBs) versus weight machines (WMs)) with the same resistance training program. Forty-five healthy sedentary middle-aged women volunteers were chosen and randomly assigned to 1 of 3 groups: 21 subjects trained using EBs (EBG), 14 in trained using WMs (WMG), and 10 were controls (CG). Both exercise groups trained with a periodized muscular endurance program twice a week for 10 weeks, with a total of 6 exercises per session for the major muscle groups. Exercise intensity was equalized by jointly monitoring the same targeted number of repetitions (TNRs) and rate of perceived exertion in active muscles (RPE-AM). Functional capacity was assessed by using knee push-up (KPU) and 60-second squat (S) tests. Body composition was measured using an 8-polar bioelectrical impedance analyzer. The results for both the EBG and WMG show a decrease in fat mass (p = 0.05 and p < 0.01, respectively) and an increase in both the fat-free mass (p < 0.05 and p < 0.01, respectively) and the number of repetitions in the KPU (p < 0.05 and p < 0.01, respectively) and S tests (p < 0.01 in both). None of the variables measured for the CG varied significantly. It can be concluded that, independently of the device used, the combined monitoring of TNRs and RPE-AM can be a valid tool for controlling the resistance exercise intensity and can lead to healthy adaptations. EBs can thus offer significant physiological benefits that are comparable to those obtained from WMs in the early phase of strength training of sedentary middle-aged women.

Influence of additional load on the moments of the agonist and antagonist muscle groups at the knee joint during closed chain exercise

The present study investigated the influence of additional loads on the knee net joint moment, flexor and extensor muscle group moments, and cocontraction index during a closed chain exercise. Loads of 8, 28, or 48 kg (i.e., respectively, 11.1 ± 1.5%, 38.8 ± 5.3%, and 66.4 ± 9.0% of body mass) were added to subjects during dynamic half squats. The flexor and extensor muscular moments and the amount of cocontraction were estimated at the knee joint using an EMG-and-optimization model that includes kinematics, ground reaction, and EMG measurements as inputs. In general, our results showed a significant influence of the Load factor on the net knee joint moment, the extensor muscular moment, and the flexor muscle group moment (all Anova p < .05). Hence we confirmed an increase in muscle moments with increasing load and moreover, we also showed an original “more than proportional” evolution of the flexor and extensor muscle group moments relative to the knee net joint moment. An influence of the Phase (i.e., descent vs. ascent) factor was also seen, revealing different activation strategies from the central nervous system depending on the mode of contraction of the agonist muscle group. The results of the present work could find applications in clinical fields, especially for rehabilitation protocols.

A Review of Resistance Exercise and Posture Realignment

Exercise has been promoted in an attempt to correct postural deviations, such as excessive lumbar lordosis, scoliosis, kyphosis, and abducted scapulae. One of the assumed causes of these conditions is a weak and lengthened agonist muscle group combined with a strong and tight antagonist muscle group. Strengthening and stretching exercises have been prescribed accordingly. It is implied that strengthening exercises will encourage adaptive shortening of the muscle-tendon length, reposition skeletal segments, and produce static posture realignment. A review of the literature has found a lack of reliable, valid data collected in controlled settings to support the contention that exercise will correct existing postural deviations. Likewise, objective data to indicate that exercise will lead to postural deviations are lacking. It is likely that exercise programs are of insufficient duration and frequency to induce adaptive changes in muscle-tendon length. Additionally, any adaptations from restricted range-of-movement exercise would likely be offset by daily living activities that frequently require the body segments to go through full ranges of motion.

Motor response of the leg muscles produced by position-selective stimulation of spinal nerve roots.

To define and measure motor responses of the leg muscles in the ankle associated with position-selective and tetanic stimulation of spinal nerve roots L3-S1. Sixteen lumbosacral spinal nerve roots in 14 subjects were stimulated intraoperatively after surgical exposure and decompression for a herniated disc. Each contact of a spiral cuff multielectrode was wrapped around the root and used to excite a spatially defined population of axons beneath the electrode. The motor response from each stimulated position was evaluated in terms of three-dimensional vector torque in the ankle. Each position at which the stimulating electrode was placed around the root exhibited the same vector torque qualitatively, but at different thresholds. The root was most excitable ventrally. The S1 roots responded with a uniform three-dimensional torque pattern: plantar flexion plus lateral leg and foot rotation plus inversion. All L5 roots responded by plantar flexion. Dorsiflexion torque was possible only with stimulation of the L3 and L4 roots. Eversion was not possible with stimulation of the S1 roots or with most of the L5 roots. Position-selective stimulation of the extrathecal spinal nerve roots influences the threshold of the biomechanical response, the torque recruitment dynamics, and the magnitude of three-dimensional vector torque. Selective activation of some leg muscles or agonist muscle groups with stimulation of a single nerve root could not be achieved owing to the low spatial selectivity of the stimulation design and/or the low muscle specificity of motor fascicles in the root. Direct extrathecal stimulation of spinal nerve roots has some hypothetical advantages over stimulation of other sites along the peripheral nerves, owing to their unique anatomy, and may contribute to functional electrical stimulation of the lower extremities. Further investigation with a more selective multielectrode configuration and the use of multiple root stimulation is suggested.

Motor Response of the Leg Muscles Produced by Position-selective Stimulation of Spinal Nerve Roots

OBJECTIVE To define and measure motor responses of the leg muscles in the ankle associated with position-selective and tetanic stimulation of spinal nerve roots L3–S1. METHODS Sixteen lumbosacral spinal nerve roots in 14 subjects were stimulated intraoperatively after surgical exposure and decompression for a herniated disc. Each contact of a spiral cuff multielectrode was wrapped around the root and used to excite a spatially defined population of axons beneath the electrode. The motor response from each stimulated position was evaluated in terms of three-dimensional vector torque in the ankle. RESULTS Each position at which the stimulating electrode was placed around the root exhibited the same vector torque qualitatively, but at different thresholds. The root was most excitable ventrally. The S1 roots responded with a uniform three-dimensional torque pattern: plantar flexion plus lateral leg and foot rotation plus inversion. All L5 roots responded by plantar flexion. Dorsiflexion torque was possible only with stimulation of the L3 and L4 roots. Eversion was not possible with stimulation of the S1 roots or with most of the L5 roots. CONCLUSION Position-selective stimulation of the extrathecal spinal nerve roots influences the threshold of the biomechanical response, the torque recruitment dynamics, and the magnitude of three-dimensional vector torque. Selective activation of some leg muscles or agonist muscle groups with stimulation of a single nerve root could not be achieved owing to the low spatial selectivity of the stimulation design and/or the low muscle specificity of motor fascicles in the root. Direct extrathecal stimulation of spinal nerve roots has some hypothetical advantages over stimulation of other sites along the peripheral nerves, owing to their unique anatomy, and may contribute to functional electrical stimulation of the lower extremities. Further investigation with a more selective multielectrode configuration and the use of multiple root stimulation is suggested.

Relationships between motor-unit number estimates and isometric strength in distal muscles in ALS/MND

Measurement of progression in amyotrophic lateral sclerosis/motor neuron disease (ALS/MND) is useful for charting the natural history and assessing efficacy in drug trials. Common measures are maximal voluntary isometric contraction (MVIC) which mainly focuses on proximal muscles, and electrophysiologic measures of the compound muscle action potential (CMAP) and motor-unit number estimation (MUNE) which focus on distal muscles. We have undertaken a study to compare the relationships between MVIC, CMAP and MUNE recorded in intrinsic hand muscles of 10 subjects with ALS/MND. Grip and pinch (between the first and fifth digits) MVIC were recorded. The CMAP and MUNE (determined by the multipoint stimulation technique) were recorded from thenar and hypothenar muscle groups. To facilitate comparisons between strength and electrophysiologic measures, the MUNE values and the CMAP values from the thenar and hypothenar muscle groups were each summed. Test-retest correlations were high for all measures ( r = 0.75–0.99). Pinch and grip MVIC were highly correlated ( r = 0.83). However, MVIC measures showed weaker correlations with summed MUNE values (pinch r = 0.56, grip r = 0.64) and summed CMAP values (pinch r = 0.58 and grip r = 0.65). The weak correlations between MVIC and electrophysiologic measures are due to two factors. First, grip and pinch MVIC are correlated through co-activation of agonist muscle groups, for we recorded strong concomitant muscle activity from forearm flexor muscles during pinch. In contrast, CMAP and MUNE reflect measurement from isolated muscle groups in the hand. Second, MVIC and the CMAP are affected by collateral reinnervation and only indirectly assess motor-unit loss, while MUNE is uninfluenced by reinnervation and directly addresses the degree of motor-unit loss. These factors determine the information available from endpoint measures. We offer guidelines for choosing useful measures based upon the goals of a given study.

Hemodynamics During a Machine-Aided Flexibility Protocol

Heart rates and systolic and diastolic blood pressures of 15 subjects were measured before, during, and after a series of four proprioceptive neuromuscular facilitation (PNF) flexibility exercises. The protocol for the study involved the use of two new machines, one designed to increase flexibility of the erector spinae, the other the hamstrings. Each machine provided constant feedback of isometric force, angular displacements, time of contraction, repetitions, and other exercise variables. Each bout of exercise involved an isometric contraction of the lengthened agonist muscle group (12 sec) followed by a concentric contraction of its antagonist in order to place the body part in a more stretched position. Hemodynamic measurements were determined at both a perceived maximal voluntary isometric contraction (MVIC) and at 50% MVIC. Significant increases in hemodynamic factors were observed when exercise measures were compared to pre- and postexercise (resting) values. Higher values, though not significantly so, were found at MVIC than at 50% MVIC on both machines. All values were well within the guidelines of the American College of Sports Medicine.

Electromyostimulation from a Clinical Perspective

A proliferation of the research analysis and clinical use of electromyostimulation has occurred in sports medicine in the last decade. This manuscript will review the important findings from a clinical perspective. Specifically, this article will address the advantages of electromyostimulation over voluntary exercise indicating its greater effectiveness in the early period of rehabilitation when reflex inhibition is dominant. Other advantages of electromyostimulation include its: usefulness in training one component of an agonist muscle group; effectiveness during joint immobilisation; and possible role in altering specific muscle fibre types and enzymes. In order to facilitate the use of electromyostimulation a number of factors require consideration including proper selection of stimulus parameters, joint position and electrode size, type and placement. In addition, the research findings relative to the use of electromyostimulation at different stages of recovery as well as the concern of whether electromyostimulation should be used with or without voluntary activation of the muscle are addressed. There have been few clinical studies of the use of electromyostimulation after peripheral joint injury. The studies that have been performed focus primarily on quadriceps femoris rehabilitation after knee injury and these were classified according to diagnostic groups and discussed in this article. Finally, directions for future research are described with the hope that the great scientific effort displayed to date will be continued.