EMG power spectrum analysis of first dorsal interosseous muscle in pianists.

PURPOSE: Long-term piano training may induce potential biochemical and structural adaptations in hand intrinsic muscles or alter the motor strategy in the nervous systems. METHODS: This study investigated, by electromyography (EMG) and strain gauge, whether this pedagogical training is aerobic or anaerobic by nature. Changes in EMG power spectrum during incremental isometric muscle contractions before and after a sustained, fatiguing muscular performance were studied in the first dorsal interosseous muscle (FDI) of 13 female pianists and 15 sedentary controls. The maximal voluntary contraction (MVC) force of the FDI and the time needed to induce fatigue were also measured. RESULTS: During fatigue, the median frequency (MF) shifted toward the low frequencies in both groups. The MF of 50% and 25%MVC subsequent to fatigue were significantly lower than those before fatigue in the control group (104.0 +/- 45.5 Hz vs 116.7 +/- 41.4 Hz at 50%, P < 0.05; 114.7 +/- 43.4 Hz vs 123.3 +/- 46.7 Hz at 25%, P < 0.05). There were no significant MF changes within the pianists before and after fatigue. The root mean squares (RMS) of 50%, 25%, and 10%MVC of control subjects after fatigue were significantly higher than those before fatigue, but not in pianists. There was no difference in MF and RMS between the two groups at any level of %MVC before or after fatigue, but the pianists tended to show higher MF at each level of %MVC. Although the MVC was similar in both groups, the pianists, however, needed a much longer time to induce fatigue than controls (14.3 +/- 5.8 min vs 5.8 +/- 3.3 min, P < 0.005). CONCLUSIONS: These observations are discussed in terms of the training-induced metabolic adaptations, the changes in the strategy of motor unit recruitment, and the possibility of differences in muscle fiber composition. This study indicates that piano training should not be classified as power training, rather as endurance training. Such findings may also provide information about fine motor training for athletes and other professionals.

Triangular fibrocartilage perforations with bilateral negative ulnar variant wrists: a case report.

Triangular fibrocartilage (TFC) constitutes the major part in the triangular fibrocartilage complex, which stabilizes the distal radioulnar joint and functions as a cushion for axial compression forces. Tears in the TFC are often encountered with positive ulnar variance and regarded as part of a degenerative process of the ulnocarpal joint. They are occasionally seen as the result of trauma and are less likely to be found in a young population, especially in those who are in the first two decades of life, without causative traumatic injury. We report the case of a 12-year-old boy with bilateral negative ulnar variances with incidental findings of TFC tears in both wrists. This is a rare case, as he had no history of a traumatic event.

Compound muscle action potential amplitude and area changes in normal subjects and patients with carpal tunnel syndrome.

Lesions of mixed peripheral nerves are often diagnosed by means of electrodiagnostic tests, especially by motor and sensory conduction studies. In order to clarify the varying degrees of motor nerve involvement in patients with carpal tunnel syndrome (CTS), we designed this study for comparing the results of compound muscle action potential (CMAP) amplitude and area under the negative phase between normal persons (n = 662) and patients having CTS (n = 250). The CTS cases were categorized into two distinct groups, i.e., CTS-D (n = 120) having prolonged median sensory latency and normal needle examination, CTS-AD having prolonged median sensory latency and abnormal needle findings (n = 130). Subjects in the CTS-AD group showed significant reduction, both in CMAP amplitude and area from 3rd to 7th decades; however, in the CTS-D group there were significantly smaller CMAP amplitude from 5th to 7th decades but CMAP area demonstrated wide variations. These data indicate that CMAP amplitude and area are helpful in documenting motor nerve axonal loss, but care must be exercised when attempt is made to define axonal loss based either on area or amplitude because of the temporal dispersive effects.

Chronically stressed wrists in adolescent gymnasts: MR imaging appearance.

PURPOSE: To investigate the magnetic resonance (MR) imaging appearance of a chronically stressed wrist and to assess the utility of MR imaging for evaluation of injuries to the growth plate. MATERIALS AND METHODS: Coronal T1-weighted spin-echo and gradient-echo MR images were obtained of 93 wrists in 47 high-risk gymnasts of a Chinese opera school. MR imaging and radiographic findings were correlated in 93 wrists. RESULTS: The major MR imaging abnormalities of 47 radii with abnormal radiographic findings were horizontal fractures (n = 23), physeal cartilage extension to metaphysis (n = 17), and physeal widening (n = 17). The major MR abnormalities of 46 radii with normal radiographs included physeal cartilage extension (n = 12), metaphyseal bone bruise (n = 8), and vertical fractures (n = 4). CONCLUSION: Physeal cartilage extension into the metaphysis represents a healing sign in chronically stressed adolescent wrists. MR imaging findings including horizontal fracture and physeal cartilage extension to the metaphysis suggest that physeal widening occurred secondary to metaphyseal injury.

Wrist injuries in adolescent gymnasts of a Chinese opera school: radiographic survey.

PURPOSE: To determine the prevalence of chronic wrist injuries among adolescent gymnasts and the consequences of repetitive stress. MATERIALS AND METHODS: Students of a Chinese opera school underwent radiography of both wrists and answered a questionnaire. They were separated into study (n = 261) and control (n = 63) groups according to participation in or abstinence from exercise training, respectively. They were further separated into fused and unfused physis subgroups. The ulnar variance was measured on posteroanterior radiographs. Abnormalities of distal radii were investigated. RESULTS: An increase in both mean ulnar variance and frequency of ulnar-plus variance was noted in the study subgroups. Fourteen (8.2%) of 170 wrists of the fused physis study subgroup had an exceedingly large ulnar-plus variance. Sixty-one (17.3%) of 352 wrists had abnormal morphology of the distal radii in the unfused physis study subgroup. Widening of the physis was the most common finding. CONCLUSION: Chronic, repetitive stress in the wrists of adolescent gymnasts results in a localized growth disturbance of the distal radius with resultant ulnar-plus variance. Stress injuries of the physis may lead to permanent sequelae, even in asymptomatic individuals.

Body composition and two-compartment model assumptions in male long distance runners.

Long distance running increases bone mineral mass, skeletal muscle weight, and extracellular fluid volume. Each of these changes may have an impact on classic two-compartment body composition methods that assume a constant fat-free body mass (FFM) density (1.100 g.cc-1), potassium content (65 mmol.kg-1 FFM), and hydration (0.73 kg H2O.kg-1 FFM). The aims of the present study were: to use newly developed multi-component methods to evaluate the validity of two-compartment methods in white male recreational long-distance runners (N = 10); and to compare the body composition of these runners to sedentary controls (N = 10) of similar age, body weight, and body mass index. Runners had a significantly smaller fraction of body weight as fat (P = 0.001) and a larger fraction of FFM as lower extremity skeletal muscle (P = 0.045) and bone (P = 0.049). Although FFM constituted a larger proportion of body weight in the runners, the fractional contributions of water, protein, and mineral were similar to those in the control group. There were no significant differences between the two groups in density of FFM, total body potassium/FFM, and total body water/FFM. New methods thus allow in-depth analyses of body composition in athletes, with results suggesting that classic two-compartment methods are valid in white recreational long-distance runners.