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PubMed1990

[A case of long thoracic nerve palsy, with winged scapula, as a result of prolonged exertion on practicing archery].

Reports of isolated long thoracic nerve palsy are rare in Japan. We reported a case of isolated long thoracic nerve palsy, resulted from recurrent injury to the nerve. Muscle CT and electrodiagnostic study were useful for confirming diagnosis of this cases. This patient was a student aged 20 years, with nothing of importance in his family or past history. After he started practicing archery, winging of left scapula was gradually developed. Physical examination revealed weakness and atrophy of left serratus anterior muscle. There was no wasting and weakness of other should girdle muscles. Hematochemical tests were normal, except slight hyperthyroidism. Radiography and myelography of the cervical spine were normal. Muscle CT of upper thoracic level demonstrated atrophy of left serratus anterior muscle, and no abnormality were found in other muscles. Electromyogram of the left serratus anterior revealed discrete activity of reduced amplitude, and fibrillation potentials and positive sharp waves. Conduction time for left long thoracic nerve was prolonged, and amplitude of the evoked response was small and there were temporal dispersion. Muscle CT and electrodiagnostic studies were suggestive of neuroapraxia of left long thoracic nerve. Over stretching or compression during exercises may be responsible for the damage to the long thoracic nerve.

Adult↗
PubMed2004

Contribution of afferent feedback to the soleus muscle activity during human locomotion.

During the stance phase of the human step cycle, the ankle undergoes a natural dorsiflexion that stretches the soleus muscle. The afferent feedback resulting from this stretch enhances the locomotor drive. In this study a robotic actuator was used to slightly enhance or reduce the natural ankle dorsiflexion, in essence, mimicking the small variations in the ankle dorsiflexion movement that take place during the stance phase of the step cycle. The soleus (SOL) and tibialis anterior EMG were analyzed in response to the ankle trajectory modifications. The dorsiflexion enhancements and reductions generated gradual increments and decrements, respectively, in the ongoing SOL EMG. We exercised care to ensure that the imposed ankle movements were too slow to elicit distinct burst-like stretch reflex responses that have been investigated previously. The increased SOL EMG after the dorsiflexion enhancements was reduced when the group Ia afferents were blocked with peripheral ischemia at the thigh, and during high-frequency Achilles tendon vibration. However, neither ischemia nor tendon vibration affected the decrements in the SOL EMG during the dorsiflexion reductions. These findings give evidence of the contribution of afferent feedback to the SOL activity in an ongoing basis during the stance phase. The results suggest that mainly feedback from the group Ia pathways is responsible for the increments in the SOL EMG during the dorsiflexion enhancements. However, the decrements in the SOL activity might be mediated by different afferent mechanisms.

Adult↗
PubMed2004

Muscle plasticity after weight and combined (weight + jump) training.

PURPOSE: The purpose of this study was to compare the effects of jump training as a complement to weight training on jump performance and muscle strategy during the squat and countermovement jump. METHOD: Twenty-two male handball players, between the ages of 17 and 24, and in good health, were randomly divided into three groups. Two were trained groups, weight training (WTG) and jump training combined with weight training (CTG), and one was a control group (CG). Maximal isometric force and maximal concentric power were assessed by a supine leg press, squat jump (SJ), counter movement jump (CMJ), and surface EMG was used to determine changes in muscle adaptation before and after the training period. RESULTS: After 6-wk training programs, the two training groups increased maximal isometric force, maximal concentric power, and squat jump performance. However, only combined training presented a significant increase in height jump performance during the countermovement jump (P < 0.05). EMG analysis (as interpreted through the root mean square values) showed that the SJ was performed similarly before and after the training period for the two training groups. However, during the CMJ, only the CTG group adopted a new technique manifested by a short transition phase together with an increase in knee joint stiffness and knee extensor muscle activation and rectus femoris ratio. CONCLUSION: It was suggested that the central activities in knee joint during the transition phase, in conjunction with intrinsic muscle contractile properties, play a major role in the regulation of performance during a CMJ. Furthermore, our study suggests that a change in maximal strength and/or explosive strength does not necessarily cause changes in combined movement such as the stretch shortening cycle.

Electromyography↗
PubMed2000

Passive energy return after repeated stretches of the hamstring muscle-tendon unit.

UNLABELLED: It has been shown that five repetitive static stretches of human hamstring muscle, each lasting 90 s and separated by 30 s, altered the passive properties on a short-term basis. However, a total of 7.5 min (5 x 90 s) of stretching for a single muscle group may be an unrealistic stretching program. PURPOSE: The present investigation examined whether three repeated 45-s static stretches had a measurable effect on the passive properties of the hamstring muscle-tendon unit, in vivo. METHODS: Resistance to stretch was defined as the passive moment (Nm) offered by the hamstring muscle group during passive knee extension using a KinCom dynamometer as previously described (Kinetic Communicator, Chattecx Corp., Chattanooga, TN). The static stretch exercise was administered to the left lower extremity of all subjects and consisted of a dynamic phase of passive knee extension to a predetermined final joint angle followed by a 45-s static phase. The procedure was repeated for a total of three 45-s static stretches with 30-s rest period between stretches. RESULTS: There was a significant decline in resistance over the 45-s the static phase in stretch 1 (20 +/- 3%) and stretch 3 (18 +/- 3%), P < 0.001. Further, the absolute or relative decline in resistance over time stretch 1 and 3 were equivalent. The mean resistance in stretch 1 and 3, expressed as the log(e) of time, yielded an equal and highly linear relationship (r2 = 0.96 +/- 0.01); the slope and intercept did not differ. In the dynamic phase of the stretch, the energy of stretch 1 and 3 were similar. CONCLUSIONS: These data suggest that the static stretching protocol used in the present study had no short-term effect on the viscoelastic properties of human hamstring muscle group.

Adult↗
PubMed1999

Effects of ipsilateral anterior thigh soft tissue stretching on passive unilateral straight-leg raise.

STUDY DESIGN: Randomized 3-group pretest-posttest with blind assessment of outcome. OBJECTIVES: The purpose of this study was to examine the effect of sagittal plane hold-relax exercise applied to the ipsilateral anterior thigh, and prone positioning on passive unilateral straight-leg raise measurements. BACKGROUND: Straight-leg raising has been viewed as a measurement for hamstring muscle length, but literature suggests that other structures may affect this measurement. METHODS AND MEASURES: Sixty subjects (45 men, 15 women) qualified for inclusion into the study based on a straight-leg raise measurement of < or = 65 degrees. Subjects were randomly assigned to one of three groups: control, static stretch, or sagittal plane hold-relax exercise. Pretest and posttest straight-leg raise measurements of the right lower extremity were performed for each subject. RESULTS: A 1-way ANOVA of the change scores showed a significant difference between groups. A Tukey post hoc analysis of the change scores showed that both treatment groups' means differed significantly from the control group and from each other, with the sagittal plane hold-relax group exhibiting the largest change (mean of 7.8 degrees +/- 2.8 degrees). CONCLUSIONS: The results of this study show that sagittal plane hold-relax exercise and passive prone results of this study show that sagittal plane hold-relax and passive prone positioning can significantly increase straight-leg raise range of motion, however the sagittal plane hold-relax stretching of the anterior thigh is more effective than passive prone positioning.

Adult↗
PubMed2001

Reflex and intrinsic changes induced by fatigue of human elbow extensor muscles.

Fatigue-induced changes in intrinsic and reflex properties of human elbow extensor muscles and the underlying mechanisms for fatigue compensation were investigated. The elbow joint was perturbed using small-amplitude and pseudorandom movement patterns while subjects maintained steady levels of mean joint extension torque. Intrinsic and reflex properties were identified simultaneously using a nonlinear delay differential equation model. Intrinsic joint properties were characterized by measures of joint stiffness, viscous damping, and limb inertia and reflex properties characterized by measures of dynamic and static reflex gains. Fatigue was induced using 15 min of intermittent voluntary isometric (submaximal) exercise, and a rest period of 10 min was taken to allow the fatigued muscles to recover from acute fatigue effects. Identical experimental and data analysis procedures were used before and after fatigue. Our findings were that after fatigue, joint stiffness was significantly reduced at higher torque levels, presumably reflecting the reduced force-generating capacity of fatigued muscles. Conversely, joint viscosity was increased after fatigue potentially because of the reduced crossbridge detachment rate and prolonged relaxation associated with intracellular acidosis accompanying fatigue. Static stretch reflex gain decreased significantly at higher torque levels after fatigue, indicating that the isometric fatiguing exercise might be associated with a preferential change in properties of spindle chain fibers and bag(2) fibers. For matched pre- and postfatigue torque levels, dynamic reflexes contributed relatively more torque after fatigue, displaying higher dynamic reflex gains and larger dynamic electromyographic responses elicited by the controlled small-amplitude position perturbations. These changes appear to counteract the fatigue-induced reductions in joint stiffness and static reflex gain. The compensatory responses could be partly due to the effects of increasing the number of active motoneurons innervating the fatiguing muscles. This shift in operating point gave rise to significant compensation for the loss of contractile force. The compensation could also be due to fusimotor adjustment, which could make the dynamic reflex gain much less sensitive to fatigue than intrinsic stiffness. In short, the reduced contribution from intrinsic stiffness to joint torque was compensated by increased contribution from dynamic stretch reflexes after fatigue.

Adult↗
PubMed2006

Maximal lengthening contractions increase p70 S6 kinase phosphorylation in human skeletal muscle in the absence of nutritional supply.

The aim of this study was to compare the training stimuli of eccentric (lengthening) and concentric (shortening) contractions regarding the effect on signaling enzymes involved in protein synthesis. Ten male subjects performed 4 x 6 maximal eccentric contractions on one leg followed by 4 x 6 maximal concentric contractions on the other. Six additional subjects performed the same protocol, but with maximal concentric and submaximal eccentric exercise of equal force to that of the maximal concentric contractions. Muscle biopsy samples were taken from the vastus lateralis before, immediately after, and 1 and 2 h after exercise in both legs. The average peak force produced during the maximal eccentric exercise was 31% higher than during the maximal concentric exercise, 2,490 (+/-100) vs. 1,894 (+/-108) N (P < 0.05). The maximal eccentric contractions led to two- to eightfold increases in the phosphorylation of p70 S6 kinase (p70(S6k)) and the ribosomal protein S6 that persisted for 2 h into recovery but no significant changes in phosphorylation of Akt or mammalian target of rapamycin (mTOR). Maximal concentric and submaximal eccentric contractions did not induce any significant changes in Akt, mTOR, p70(S6k), or S6 phosphorylation up to 2 h after the exercise. The results indicate that one session of maximal eccentric contractions activates p70(S6k) in human muscle via an Akt-independent pathway and suggest that maximal eccentric contractions are more effective than maximal concentric contractions in stimulating protein synthesis in the absence of a nutritional intake, an effect that may be mediated through a combination of greater tension and stretching of the muscle.

Adult↗
PubMed1984

Biomechanics and neuromuscular performance.

Research of neuromuscular performance offers a unique possibility for integration of biomechanics, muscle physiology, and neurophysiology. This integration is especially desirable in situations where recording of neuromuscular function is made under normal movement conditions of the entire physiological range. This would improve the possibilities to investigate more exactly the interrelationship between structural aspects of the neuromuscular system and performance characteristics. Stretch-shortening cycle, a normal way of muscle function needs also to be investigated more both from the neurophysiological and mechanical viewpoints. Understanding of this stretch-shortening cycle would improve our possibilities to examine the mechanical efficiency of exercise more objectively. This paper discusses these aspects in an attempt to outline directions for future research in neuromuscular performance.

Biomechanical Phenomena↗
PubMed2005

Effects of isometric squat training on the tendon stiffness and jump performance.

The present study aimed to investigate the effect of isometric squat training on human tendon stiffness and jump performances. Eight subjects completed 12 weeks (4 days/week) of isometric squat training, which consisted of bilateral leg extension at 70% of maximum voluntary contraction (MVC) for 15 s per set (10 sets/day). Before and after training, the elongations of the tendon-aponeurosis complex in the vastus lateralis muscle and patella tendon were directly measured using ultrasonography while the subjects performed ramp isometric knee extension up to MVC. The relationship between the estimated muscle force and tendon elongation was fitted to a linear regression, the slope of which was defined as stiffness. In addition, performances in two kinds of maximal vertical jumps, i.e. squatting (SJ) and counter-movement jumps (CMJ), were measured. The training significantly increased the volume (P < 0.01) and MVC torque (P < 0.01) of the quadriceps femoris muscle. The stiffness of the tendon-aponeurosis complex increased significantly from 51 +/- 22 (mean +/- SD) to 59 +/- 24 N/mm (P = 0.04), although that of the patella tendon did not change (P = 0.48). The SJ height increased significantly after training (P = 0.03), although the CMJ height did not (P = 0.45). In addition, the relative difference in jump height between SJ and CMJ decreased significantly after training (P = 0.02). These results suggest that isometric squat training changes the stiffness of human tendon-aponeurosis complex in knee extensors to act negatively on the effects of pre-stretch during stretch-shortening cycle exercises.

Adult↗
PubMed1998

[Effects of a short-term pulmonary rehabilitation program on patients with chronic respiratory failure due to pulmonary emphysema].

To evaluate the effects of a short-term pulmonary rehabilitation program on dyspnea, exercise capacity, and lung function, 15 patients with chronic respiratory failure due to pulmonary emphysema were enrolled in such a program for 3 weeks as inpatients. The program consisted of pursed lip breathing, diaphragmatic breathing, respiratory muscle stretch gymnastics, and walking with synchronized breathing. Dyspnea as measured with a visual analogue scale at the end of a 6-minute walk before and after the program (49.7 +/- 4.0% to 24.2 +/- 3.8%) decreased significantly (p < 0.01). As a measure of functional exercise capacity, the 6-minute walking distance (226.9 +/- 32.4 m to 292.1 +/- 35.8 m) increased significantly (p < 0.01). As an indicator of maximal exercise capacity, endurance time on an incremental treadmill test did not improve. Spirometric data did not change during the study. Total lung capacity (TLC) (8.44 +/- 0.70 L to 7.58 +/- 0.74 L) and residual volume (RV) (5.13 +/- 0.53 L to 4.28 +/- 0.59 L) decreased significantly (p < 0.01). The findings suggest that this program relieves dyspnea, increases functional exercise capacity, and decreases TLC and RV on patients with chronic respiratory failure due to pulmonary emphysema.

Aged↗
PubMed1996

Sport stretching: effect on passive muscle stiffness of short hamstrings.

OBJECTIVE: To evaluate the effects of one 10-minute stretch on muscle stiffness in subjects with short hamstrings. DESIGN: Randomized control trial. SETTING: Laboratory for human movement sciences in the department of rehabilitation of a university hospital. SUBJECTS: Sixteen students from the Department of Human Movement Sciences participated with informed consent in the experiment. Subjects were limited to men and women without a history of neurological and orthopedic disorders. To select subjects with short hamstrings, the finger-ground distance had to be greater than 0cm (unable to touch the floor when bending forward) and the manual leg lifting was not to exceed 80 degrees. One group of 10 subjects performed static stretching exercises during 10 minutes interspersed with relaxing, whereas the untreated group of 6 subjects was used as a control. MAIN OUTCOME MEASURES: The instrumental straight-leg-raising set-up enables the measurement of the force needed to lift the leg, range of motion (ROM), pelvic-femoral angle, and the electromyogram of the hamstrings. These variables provide information about the stiffness, elongation, and state of activity of the hamstring muscles. RESULTS. One 10-minute sport stretch resulted in a significant increase in passive muscle moment, ROM, and elongation of the hamstrings. There was no significant change in the course of the passive muscle stiffness curve with respect to the prestretch stiffness curve. CONCLUSIONS: One session of static stretching does not influence the course of the passive muscle stiffness curve. The increased ROM, i.e., the extensibility of the hamstrings, results from an increase in the stretch tolerance.

Adult↗
PubMed1990

Regulation of satellite cells during skeletal muscle growth and development.

Satellite cells are myogenic cells attributed with the role of postnatal growth and regeneration in skeletal muscle. Following proliferation and subsequent differentiation, these cells will fuse with one another or with the adjacent muscle fiber, thereby increasing myonuclei numbers for fiber growth and repair. The potential factors which could regulate this process are many, including exercise, trauma, passive stretch, innervation, and soluble growth factors. Three classes of growth factors in particular (fibroblast growth factor, insulin-like growth factor, and transforming growth factor-beta) have been studied extensively with respect to their effects on satellite cell proliferation and differentiation in culture. Fibroblast growth factor has been shown to stimulate proliferation but depress differentiation. Insulin-like growth factor stimulates both proliferation and differentiation, although the latter to a much greater degree. Transforming growth factor-beta slightly depresses proliferation but inhibits differentiation. When administered in combination, these factors can induce satellite cell activities in culture which mimic those typical of satellite cells found in vivo in growing, regenerating, or healthy mature muscle. Alterations in the concentrations of these growth factors in the muscle environment as well as alterations in the cell's sensitivity or responsiveness to these factors represent potential mechanisms for regulating satellite cell activity in situ.

Animals↗
PubMed2005

Contribution of the tendinous tissue to force enhancement during stretch-shortening cycle exercise depends on the prestretch and concentric phase intensities.

When the prestretch intensity and concentric work are increased in stretch-shortening cycle (SSC) exercises, the utilization of the elastic energy can increase during the concentric phase. In order to further understand this process during SSC exercises, the interaction between fascicle-tendinous tissues (TT) of the vastus lateralis (VL) muscle was examined under different prestretch and rebound intensity drop jumps. Ten male subjects participated in the study. Direct VL fascicle lengths (N = 10) and in vivo patellar tendon force (N = 1) were measured together with the electromyographic (EMG) activity of VL during the trials. With increasing drop height but the same rebound height condition, the TT stretch increased during the early braking phase with a subsequent increase in its recoil during the early push-off phase. This occurred concomitantly with decreased fascicle shortening and EMG activation. However, with the increased rebound height but the same drop height condition, the fascicles were stretched less during the late braking phase with higher EMG activation. In this situation, TT could be stretched more by the tension provided by fascicles. Consequently, the TT recoil increased during the late push-off phase. These observations confirm that there can be an intensity specific fascicle-TT interaction during SSC exercises.

Adaptation, Physiological↗
PubMed1991

Exercise-related changes in protein turnover in mammalian striated muscle.

Contractile activity is an important determinant of the size, rate of protein turnover and phenotypic properties of muscle. Animal models that decrease muscle activity invariably accelerate the rate of protein degradation, usually complementing decreases in the rate of protein synthesis. The net effect is muscle atrophy. By contrast, increased activity and/or passive stretch enhance the synthesis of new proteins, whilst protein catabolism may be either decreased or increased. Muscle hypertrophy results. Endurance activities in man and animals usually induce cardiac hypertrophy, and increased fatigue resistance in skeletal muscle. During exercise the whole body and its skeletal musculature exhibit a negative nitrogen balance, and there is general agreement that rates of protein synthesis are decreased. Changes in protein degradation are, however, much less clearly defined. Resistance exercises induce the opposite changes, with the size of the heart remaining unchanged whilst the bulk and strength of skeletal muscle increase. No real consensus currently exists about the nature of the changes in protein turnover with this type of exercise. More carefully designed and executed experiments are required.

Animals↗