When active muscles lengthen: properties and consequences of eccentric contractions.
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Adaptation, Physiological↗
Biomedical subjects
P C LaStayo
Publications and source records attributed to P C LaStayo.
Eccentric ergometry: increases in locomotor muscle size and strength at low training intensities.
Lengthening (eccentric) muscle contractions are characterized by several unusual properties that may result in unique skeletal muscle adaptations. In particular, high forces are produced with very little energy demand. Eccentrically trained muscles gain strength, but the specific nature of fiber size and composition is poorly known. This study assesses the structural and functional changes that occur to normal locomotor muscle after chronic eccentric ergometry at training intensities, measured as oxygen uptake, that do not influence the muscle when exercised concentrically. Male subjects trained on either eccentric or concentric cycle ergometers for 8 wk at a training intensity starting at 54% and ending at 65% of their peak heart rates. The isometric leg strength increased significantly in the eccentrically trained group by 36%, as did the cross-sectional area of the muscle fiber by 52%, but the muscle ultrastructure remained unchanged. There were no changes in either fiber size, composition, or isometric strength in the concentrically trained group. The responses of muscle to eccentric training appear to be similar to resistance training.
Adult↗
Is the spring quality of muscle plastic?
During locomotion, major muscle groups are often activated cyclically. This alternate stretch-shorten pattern of activity could enable muscle to function as a spring, storing and recovering elastic recoil potential energy. Because the ability to store and recover elastic recoil energy could profoundly affect the energetics of locomotion, one might expect this to be an adaptable feature of skeletal muscle. This study tests the hypothesis that chronic eccentric (Ecc) training results in a change in the spring properties of skeletal muscle. Nine female Sprague-Dawley rats underwent chronic Ecc training for 8 wk on a motorized treadmill. The spring properties of muscle were characterized by both active and passive lengthening force productions. A single "spring constant (Deltaforce/Deltalength) from the passive length-tension curves was calculated for each muscle. Results from measurements on long heads of triceps brachii muscle indicate that the trained group produced significantly more passive lengthening force (P = 0.0001) as well as more active lengthening force (P = 0.0001) at all lengths of muscle stretch. In addition, the spring constants were significantly different between the Ecc (1.71 N/mm) and the control (1.31 N/mm) groups. A stiffer spring is capable of storing more energy per unit length stretched, which is of functional importance during locomotion.
Animals↗
Exercise training in chronic hypoxia has no effect on ventilatory muscle function in humans.
At the highest altitude, aerobic work is limited by environmental oxygen availability. We therefore reasoned that the hyperpnea associated with endurance training at altitude should provide a strong stimulus for adaptation of the ventilatory muscles. We measured peak inspiratory muscle pressure-flow characteristics (inspiring through graded resistors) and maximum sustainable ventilation capacity in ten permanent residents of La Paz, Bolivia (3600 m) prior to and immediately following 6 weeks of incremental endurance training. Additionally, eight local residents did no training and functioned as controls for the capacity test. While V(O2)max measured in hypoxia increased by 19% (Favier et al., 1995b. J. Appl Physiol. 78, 2286-2293.), none of the tested ventilatory variables showed significant changes. The values for the group mean slopes of maximum inspiratory pressure-flow pairs (- 10.5 vs. - 9.8 cm H2O x sec x L(-1), P=0.301; before versus after training, respectively), maximum inspiratory pressure (112.1+/-8.9 vs. 106.9+/-8.6 cmH2O, P=0.163), peak inspiratory flow (9.8+/-0.41 vs. 10.2+/-0.55 L x sec(-1) P=0.172) and the maximum volitional volume in 12 sec (43.9+/-2.4 vs. 45.6+/-2.4 L in 12 sec, P=0.133) were unchanged with exercise training. Likewise, maximal sustainable minute volume was not different between post-training and control subjects (177.4+/-7.9 vs. 165.4+/-8.4 L x min(-1), P=0.141). These data support the concept that endurance training fails to elicit functional adaptations in ventilatory muscles in humans, even when exercise is done in hypoxia.
Acclimatization↗
Electromyography of the shoulder: an analysis of passive modes of exercise.
Passive shoulder motion is standard early rehabilitation in patients undergoing rotator cuff repair. A number of rehabilitation protocols exist to obtain this goal. This article evaluated different rehabilitation protocols using electromyographic analysis of the rotator cuff muscles to determine if the different protocols promote passive motion. Ten healthy volunteers underwent EMG to investigate the relative activity of the rotator cuff muscles during various exercises used postoperatively following shoulder surgery. The exercises tested were continuous passive motion machine (CPM), pulley, pendulum, self-assisted bar raise using the contralateral arm for power, self-assisted internal and external rotation, therapist-assisted elevation in plane of the scapula, and therapist-assisted internal and external rotation. The relative activity of the supraspinatus, infraspinatus, anterior deltoid, and trapezius muscles were measured and expressed as a percentage of maximal activity. For all muscle groups tested, the pulley exercise showed significantly more activity than the CPM machine. In the supraspinatus muscle, the pulley exercise averaged 17.6% of maximal activity and 8.7% for the self-assisted bar raise using contralateral arm power compared with 5.0% for the CPM machine. In general, therapist-assisted exercises and Codman's pendulum exercises showed activity that was not significantly different from the CPM machine. These results indicate that CPM and therapist-assisted passive range of motion, by being more passive, may increase the safety margin for obtaining early passive range of motion without disrupting the rotator cuff repair.
Adolescent↗
Reliability of passive wrist flexion and extension goniometric measurements: a multicenter study.
BACKGROUND AND PURPOSE: The purpose of this study was twofold: (1) to determine whether passive wrist flexion and extension goniometric measurements using ulnar alignment, radial alignment, and volar/dorsal alignment were similar or dissimilar and (2) to examine which of these three techniques had the greatest intratester and intertester reliability. SUBJECTS: One hundred forty patients (141 wrists) were measured. The testers were 32 therapists from eight different hand/upper-extremity clinical sites around the United States. METHODS: Randomly paired testers measured passive wrist flexion and extension. The intraclass correlation coefficient (ICC) was used as an estimate of agreement for both intratherapist (model 3.1) and intertherapist (model 2.1) reliability. RESULTS: Six of the eight clinics showed significant differences among the various goniometric techniques. Flexion intratherapist mean ICCs for the radial, ulnar, and dorsal alignment techniques were .86, .87, and .92, respectively. Extension intratherapist mean ICCs were .80, .80, and .84 for the three techniques. Intertherapist flexion mean ICCs were .88, .89, and .93 for the radial, ulnar, and volar alignment techniques, respectively. Extension intertherapist mean ICCs were .80, .80, and .84 for the three techniques. The standard error of measurement was also used to quantify reliability, with the volar/dorsal alignment technique consistently producing less error than the ulnar and radial alignment techniques. The generalizability theory statistical model was utilized to identify the sources of error. The patient contributed to variance the most, although inherent error within the study, diagnostic category, therapeutic approach, and goniometric technique also contributed. CONCLUSION AND DISCUSSION: The overall results indicated there were differences among the three goniometric techniques. The volar/dorsal alignment technique is the goniometric technique of choice, as it consistently had the greatest reliability.
Adolescent↗
Distal radius fractures: therapy practice patterns.
Identifying practice patterns for therapy interventions following distal radius fractures (DRFs) is necessary to define the most frequently used examination and intervention techniques. The purpose of this study was to identify preferred practice patterns and physical and functional outcome measures used during DRF management. Two hundred forty-two therapists (PTs, OTs, and CHTs) were surveyed by questionnaire at an annual hand therapy meeting. A descriptive analysis of data was performed. Preferred practice patterns during the immobilization and the post-immobilization periods were identified. More than 75% of the surveyed therapists used upper extremity range-of-motion exercises and compressive wrap with retrograde massage during the immobilization phase. More than 90% of therapists included range-of-motion exercises and heat/cold modalities in the post-immobilization treatment plans. Physical impairment measures of outcome were used much more frequently than functional outcome questionnaires in assessing progress during treatment. This study advances the evidence-based practice of therapy by establishing a foundation for future research.
Evidence-Based Medicine↗
The mysterious wrist.
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Biomechanical Phenomena↗
The distal radioulnar joint: anatomy and management of disorders.
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Biomechanical Phenomena↗