Reproducibility, validity and predictors of six-minute walk test in overweight and obese adolescents with intellectual disability.

OBJECTIVES: To assess the reproducibility and validity of the six-minute walk test (6MWT) and predictors of the six-minute walk distance (6MWD) in adolescents with overweight or obesity and intellectual disability (ID). STUDY DESIGN: Sixty-one adolescents with overweight or obesity and mild-to-moderate ID (intelligent quotient [IQ] 40-70; age 14-22 years) participated in this study. To test reproducibility, 39 of the participants performed the 6MWT twice with an interval of 1 week. To test validity (n = 39), peak oxygen uptake (peak VO(2)) was measured on a bicycle ergometer. For the predictor study (n = 61), weight, height, peak VO(2) and quadriceps strength were measured, and IQ and orthopedic conditions were collected from the participants' medical records. RESULTS: There was no significant difference between the means of the two 6MWTs (571.3 vs. 576.5 m; p = 0.452). The intraclass correlation coefficient was 0.82, indicating good reliability. The smallest real difference was 82.6 m. 6MWD correlated significantly with relative peak VO(2) (ß = 0.69) indicating validity. Relative peak VO(2), height, IQ, body mass index (BMI) and quadriceps strength are predictors of the 6MWD in this population. CONCLUSION: 6MWT is a reliable and valid test in adolescents with overweight or obesity and ID. Low IQ, overweight/obesity and low physical fitness contribute to the outcome of the 6MWT.

Scapular-muscle performance: two training programs in adolescent swimmers.

CONTEXT: Swimming requires well-balanced scapular-muscle performance. An additional strength-training program for the shoulders is pursued by swimmers, but whether these muscle-training programs need to be generic or specific for endurance or strength is unknown. OBJECTIVE: To evaluate isokinetic scapular-muscle performance in a population of adolescent swimmers and to compare the results of training programs designed for strength or muscle endurance. DESIGN: Controlled laboratory study. SETTING: University human research laboratory. PATIENTS OR OTHER PARTICIPANTS: Eighteen adolescent swimmers. INTERVENTION(S): Each participant pursued a 12-week scapular-training program designed to improve either muscle strength or muscle endurance. MAIN OUTCOME MEASURE(S): Bilateral peak force, fatigue index, and protraction/retraction strength ratios before and after the scapular-training program. RESULTS: Scapular protraction/retraction ratios were slightly higher than 1 (dominant side  =  1.08, nondominant side  =  1.25, P  =  .006). Side-to-side differences in retraction strength were apparent both before and after the training program (P  =  .03 and P  = .05, respectively). After the training program, maximal protraction (P < .05) and retraction (P < .01) strength improved on the nondominant side. Peak force and fatigue index were not different between the training groups. The fatigue indexes for protraction on both sides (P < .05) and retraction on the nondominant side (P  =  .009) were higher after the training program. CONCLUSIONS: We describe the scapular-muscle characteristics of a group of adolescent swimmers. Both muscle-strength and muscle-endurance programs improved absolute muscle strength. Neither of the strength programs had a positive effect on scapular-muscle endurance. Our results may be valuable for coaches and physiotherapists when they are designing exercise programs for swimmers.

Trapezius muscle timing during selected shoulder rehabilitation exercises.

STUDY DESIGN: Controlled laboratory study. OBJECTIVES: To examine the timing of the 3 portions of the trapezius muscle in relation to the posterior deltoid (PD) muscle and in relation to one another during 4 selected shoulder exercises: (1) prone extension, (2) forward flexion in side lying, (3) external rotation in side lying, and (4) prone horizontal abduction with external rotation. BACKGROUND: Deficiencies in trapezius muscle recruitment have been identified in patients with shoulder pain. Alterations in the trapezius muscle activation level and timing have been identified in previous research. Scapular muscle exercises in which the middle trapezius (MT) and lower trapezius (LT) muscle showed optimal activity with minimal upper trapezius (UT) muscle participation have been recently identified. However, it is currently unknown if these exercises also promote early activation of the scapular stabilizing musculature. METHODS: The intermuscular and intramuscular timing of muscle activation (based on an activation level of greater than 10% maximum voluntary contraction beyond basic activity) of the 3 portions of the trapezius muscle during 4 exercises were examined by surface EMG in 30 healthy subjects on the dominant side (14 males, 16 females). A 1-sample t test was used to determine which portions of the trapezius muscle were activated significantly earlier or later than the PD (intermuscular timing). An analysis of variance for repeated measures (3 levels) was used for each exercise to determine possible timing differences among the 3 portions of the trapezius muscle (intramuscular timing). RESULTS: Intermuscular and intramuscular differences in timing of the portions of the trapezius muscle were found. The UT was activated significantly later than the PD (P<.01), and the MT was activated significantly earlier than the PD (P<.01), during the prone extension exercise. During the horizontal abduction with external rotation exercise, the MT (P<.01) and the LT (P = .01) were activated significantly earlier than the PD. During prone extension, side-lying external rotation, and prone horizontal abduction with external rotation, significant differences were found between the UT and MT, between the UT and LT, but not between the MT and LT. In these exercises the MT and LT were activated significantly earlier than the UT. During forward flexion in side lying, no significant timing differences were found between the activation of the portions of the trapezius. CONCLUSIONS: With the exception of the LT during prone extension, the prone extension exercise and the prone horizontal abduction with external rotation exercise promote early activation of the MT and LT in relation to the scapular and glenohumeral prime mover. Taking into account the limited generalizability of the results due to a narrow age range, these exercises are potentially promising for the treatment of intermuscular and intramuscular timing disorders of the trapezius muscle.