Stephen N. Stanley

Verbal encouragement: effects on maximum effort voluntary muscle: action

Objective To examine the effects of verbal encouragement on the peak force of the elbow flexors during an isometric muscle action. Methods A crossover design whereby 20 subjects were divided into 10 2×2 Latin squares was undertaken. Peak forces were measured on a Kin-Com dynamometer, and electromyographic (EMG) activity was also recorded from the biceps brachii. All subjects completed trials with and without verbal encouragement. Results Mean peak force increased (P<0.05) from 296 to 311 N (5%) when verbal encouragement was presented. A spectral analysis of the EMG activity showed no changes (P>0.05) to the median frequency in the condition where verbal encouragement was present. Conclusions These findings have ramifications for training and exercise therapy. An awareness of the effects of verbal encouragement is important when motivating athletes and patients to attain maximum performance during exercise.

Stretching at the ankle joint: viscoelastic responses to holds and continuous passive motion.

PURPOSE To compare the effect of static holds and continuous passive motion on stiffness and force relaxation of the soft tissue structures resisting ankle joint dorsiflexion. METHODS This study used a randomized repeated measures trial design. Twenty-four asymptomatic subjects (15 males and 8 females) with a mean age of 26 yr participated. A Kin-Com dynamometer was used to measure the stiffness and force relaxation response of tissues about the ankle joint in response to a plantar flexor stretch. A comparison was made of the response for a 1 x 60-s hold, 2 x 30-s holds, 4 x 15-s holds, and continuous passive motion for 60 s. All subjects undertook all conditions. The main outcome measures were 1) stiffness at the ankle joint as it moved to 80% of the maximum range of dorsiflexion, and 2) the decrease in force at 80% of the maximum range of motion of the ankle joint. RESULTS Stiffness was decreased significantly (P < 0.05) for the continuous passive motion condition only. The mean magnitude of the decrease in stiffness was 16%. Across hold times, force decreased significantly (P < 0.05). Bonferonni contrasts indicated that there was a significant difference (P < 0.05) between the continuous passive motion condition and all other hold conditions. There were no significant differences (P > 0.05) between the 4 x 15-s, 2 x 30-s, and 1 x 60-s holds. The magnitude of the decline in force was 10.5%, 21.5%, 21.7%, and 19% for the 0-, 15-, 30-, and 60-s holds, respectively. The greatest decreases in tension were achieved in the first 20 s of a hold. CONCLUSION If decreasing stiffness is a key aim of a stretching program, the findings indicate that continuous motion is more effective than holds. In contrast, if relaxation of peak tension is the main aim, then holds are most effective.

Effect of passive stretching and jogging on the series elastic muscle stiffness and range of motion of the ankle joint

Objective To determine the effect of stretching and jogging on the series elastic muscle stiffness of the plantar flexors and on the range of dorsiflexion at the ankle joint. Methods 24 healthy subjects participated in this study. Each subject undertook all of the following protocols, in random order: (1) stretching protocol: five 30 s static stretches with 30 s rest between stretches; (2) aerobic jogging protocol: subjects ran on a treadmill for 10 min at 60% of their maximum age predicted heart rate; (3) combined protocol: subjects ran first and then stretched. A damped oscillation technique was used to measure the series elastic stiffness of the plantar flexors. Dorsiflexion of the ankle was assessed with a weights and pulley system that moved the ankle joint from a neutral position into dorsiflexion passively. Electromyography was used to monitor the activity of the plantar and dorsiflexors during these procedures. The statistical analysis of these data involved an analysis of covariance Results For decreasing series elastic muscle stiffness running was more effective than stretching (P<0.05). In contrast, the results for range of motion showed that the combination protocol and the stretching only protocol were more effective than the running only protocol (P < 0.05) for increasing dorsiflexion range of motion at the ankle. Conclusions Both jogging and static stretching exercises appear to be beneficial to individuals participating in sporting activities.

Knee Bracing: Effects on Proprioception

OBJECTIVE To examine the effects of a knee sleeve type brace on the proprioceptive ability of subjects with normal knees during a dynamic tracking task. DESIGN A 2 X 2 Latin square cross over design; in each Latin square, subjects were matched for age and gender. SETTING An institution focused on clinical education. PARTICIPANTS Twenty subjects with no musculoskeletal or neurological conditions. INTERVENTIONS Each subject performed a tracking task on a Kin-Com dynamometer. Angle and force data from the Kin-Com and angle data from an electrogoniometer were sampled at 100Hz using a data acquisition program on a PC computer. The subjects were blindfolded and the limb attached to the Kin-Com was moved passively by the dynamometer. Subjects were instructed to follow the movement as closely as possible with the other limb (the tracking limb). Subject performed two trials, one without knee bracing and another that involved the application of a brace to the tracking limb. OUTCOME MEASURE The magnitude of the error in tracking was established by taking the difference of the active and passively moving limbs and calculating the root mean square (RMS) of the difference. RESULTS The findings showed that there was an improvement of 11% in tracking when subjects wore the knee brace (p < .05). CONCLUSION Alterations in proprioception as a result of bracing may be partly responsible for the improvement in knee injury statistics reported in some studies.

Pectoralis major tears: comparison of surgical and conservative treatment

Objectives—To compare objective measures of strength and subjective functional outcomes in complete distal pectoralis major tears treated either surgically or non-surgically. Methods—Twenty two pectoralis major tears were included in 21 patients. Ten were surgically repaired and 12 were managed non-surgically. Patients completed a standard questionnaire, and clinical examination and isokinetic dynamometry were carried out. Results—In patients who had surgical repair, peak torque returned to 99% of that of the uninjured side and work performed returned to 97%. For those managed conservatively, peak torque and work performed returned to only 56% of that of the uninjured side (p = 0.003 for the difference in peak torque, and p = 0.01 for work performed). Findings were independent of the strength of the patient, whether or not the dominant arm was involved, the age of the patient, and the length of time from injury or surgery to testing. Patients were grouped into one of three subjective functional outcome groups, and those who had a surgical repair had a better functional outcome. Conclusions—Surgical repair results in greater recovery of peak torque and work performed than conservative management of patients with rupture of the pectoralis major.

Stiffness and passive peak force changes at the ankle joint: the effect of different joint angular velocities

OBJECTIVE To compare peak force and stiffness at the ankle joint in response to repetitive dorsiflexion at two joint angular velocities (5 and 25 deg s(-1)). DESIGN Pre- post-repeated measures design. BACKGROUND Stretching affects the biomechanical properties of tissues. In many instances, stretching is performed in a cyclic manner. An important factor that might influence the effects of stretching is the speed at which the tissues are lengthened. METHODS Eighteen healthy subjects participated. A dynamometer repeatedly moved the ankle joint from 0 deg of dorsiflexion to 80% of maximum dorsiflexion over a 2 min period. Two joint angular velocities were examined: 5 and 25 deg s(-1). Force and angle data were recorded simultaneously. Electromyographic activity from plantar and dorsiflexor muscles was monitored. The variables of interest were peak passive force and average stiffness at the first and last repetition of motion. RESULTS Peak force was significantly higher (P < 0.05) at 25 deg s(-1) for the first repetition. At both joint angular velocities, peak passive force decreased significantly over the 2 min of motion. The decreases were 13% and 21% at 5 and 25 deg s(-1) respectively. Peak passive force was not significantly different (P > 0.05) across velocities at 2 min. Stiffness was greater at 25 deg s(-1) initially (P < 0.05), however, it decreased significantly across time. The magnitude of the decrease was 20% and 31% at 5 and 25 deg s(-1) respectively. After 2 min of motion, there was no significant difference (P > 0.05) in stiffness across the joint angular velocities examined. CONCLUSION(S) The findings showed that while significant differences existed in stiffness and peak force across angular velocities at the start of the stretching motion, the differences decreased considerably with repeated motion, and were relatively similar within 2 min. RELEVANCE It has long been thought that greater speeds of stretch are more likely to lead to muscle injury. Our findings suggest that it is most beneficial to stretch at a slow speed initially, thereafter, the speed of stretch may be increased.

Skeletal muscle mechanics in osteoporotic and nonosteoporotic postmenopausal women.

The purpose of this study was to evaluate single-joint, dynamic muscle function of osteoporotic (OST) and nonosteoporotic (N-OST) women. Knee flexor and extensor function in postmenopausal women (6th decade OST,n = 15; 7th decade OST,n = 10; 6th decade N-OST,n = 6; 7th decade N-OST,n = 5) were evaluated at five angular velocities from 60° · s−1 to 300° · s−1. All subject groups had similar anthropometric measurements, but the 6th decade N-OST group were more physically active than the age-matched OST group. The OST and N-OST women produced peak torque at similar knee angles. The 6th decade N-OST women produced significantly greater knee extensor mean peak torque and angle specific torque, and mean work than any of the other three groups (P<0.05). However, knee flexor function was equivalent throughout the groups for most comparisons, except those between the 6th decade N-OST and 7th decade OST. While previous research has shown an early loss of flexor muscle function in ageing women, our data indicated that women with osteoporosis also experience a deterioration in quadriceps muscle function not encountered within the N-OST subjects. It is possible that such a change is precipitated by reduced physical activity, and may mirror deterioration in bone mineral content.

Quadriceps muscle training in a restricted range of motion: Implications for anterior cruciate ligament deficiency

This study examined the transferability of strength gains associated with training in a limited range of motion, and at a specific joint angular velocity, to a different part of the range of motion. Work was assessed in control (N = 14) and experimental (N = 14) groups that performed baseline tests on a Kin-Com dynamometer at 1.05, 2.09, and 3.14 rad/sec, over a range of motion from 90 degrees flexion to full extension. The experimental group then underwent training consisting of three sets of eight maximum-effort knee extensions on a Kin-Com dynamometer at a joint angular velocity of 2.09 rad/sec, three times per week for 8 weeks. The range of motion at which they trained was 90 degrees to 45 degrees. After training, baseline tests were repeated in both groups. The findings showed that the work done by the quadriceps muscles of the experimental group increased significantly (p < .05) in the training range of motion across all joint angular velocities. In the untrained range of motion, the work done by the experimental group increased significantly (p < .05) only at the training angular velocity of 2.09 rad/sec. These findings provide evidence that training in a range of motion in which anterior shear forces are low can lead to changes in strength in the range of motion in which anterior shear forces are high. Hence, such exercise is of potential benefit to the anterior cruciate ligament-deficient individual.