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Purpose: The purpose of this study was to examine the influence of electrode placement over the estimated innervation zone (IZ) for the vastus lateralis, as well as proximal and distal to the estimated IZ, on the isometric torque-related patterns for electromyographic (EMG) amplitude and mean power frequency (MPF)., Methods: Eleven men performed submaximal to maximal isometric muscle actions of the dominant leg extensors. Surface EMG signals were recorded simultaneously from the vastus lateralis muscle with bipolar electrode arrangements placed over the estimated IZ, as well as proximally and distally to the estimated IZ., Results: The results indicate that the patterns of response and mean values for absolute and normalized EMG amplitude and MPF versus isometric torque over the estimated IZ were not consistently different from those away from the IZ. There were, however, mean differences among electrode-placement sites for absolute EMG amplitude values (distal site > proximal and/or estimated IZ sites by approximately 76 microVrms) that were not eliminated with normalization (proximal site > distal and/or estimated IZ sites by approximately 5% max)., Conclusion: Although these differences were not attributable to the IZ, they suggest that during isometric muscle actions, normalized EMG amplitude values from different individuals cannot be compared if the EMG signals are detected from different electrode locations over the muscle of interest.

The aims of this study were to examine the acute effects of static stretching on peak torque, work, the joint angle at peak torque, acceleration time, isokinetic range of motion, mechanomyographic amplitude, and electromyographic amplitude of the rectus femoris during maximal concentric isokinetic leg extensions at 1.04 and 5.23 rad x s(-1) in men and women. Ten women (mean +/- s: age 23.0 +/- 2.9 years, stature 1.61 +/- 0.12 m, mass 63.3 +/- 9.9 kg) and eight men (age 21.4 +/- 3.0 years, stature 1.83 +/- 0.11 m, mass 83.1 +/- 15.2 kg) performed maximal voluntary concentric isokinetic leg extensions at 1.04 and 5.23 rad x s(-1). Following the initial isokinetic tests, the dominant leg extensors were stretched using four static stretching exercises. After the stretching, the isokinetic tests were repeated. Peak torque, acceleration time, and electromyographic amplitude decreased (P< or = 0.05) from pre- to post-stretching at 1.04 and 5.23 rad . s(-1); there were no changes (P > 0.05) in work, joint angle at peak torque, isokinetic range of motion, or mechanomyographic amplitude. These findings indicate no stretching-related changes in the area under the angle - torque curve (work), but a significant decrease in peak torque, which suggests that static stretching may cause a "flattening" of the angle - torque curve that reduces peak strength but allows for greater force production at other joint angles. These findings, in conjunction with the increased limb acceleration rates (decreased acceleration time) observed in the present study, provide tentative support for the hypothesis that static stretching alters the angle - torque relationship and/or sarcomere shortening velocity.

Purpose: The purpose of this investigation was to cross-validate existing VO2max prediction equations on samples of aerobically trained males and females., Methods: A total of 142 aerobically trained males (mean +/- SD; 39.0 +/- 11.1 yr, N = 93) and females (39.7 +/- 10.1 yr, N = 49) performed a maximal incremental test to determine actual VO2max on a cycle ergometer. The predicted VO2max values from 18 equations (nine for each gender) were compared with actual VO2max by examining the constant error (CE), standard error of estimate (SEE), correlation coefficient (r), and total error (TE)., Results: The results of this investigation indicated that all of the equations resulted in significant (P < 0.006) CE values ranging from -216 to 1415 mL x min(-1) for the males and 132 to 1037 mL x min(-1) for the females. In addition the SEE, r, and TE values ranged from 266 to 609 mL x min(-1), 0.36 to 0.88, and 317 to 1535 mL x min(-1), respectively. Furthermore, the lowest TE values for the males and females represented 10% and 12% of the mean actual VO2max values, respectively., Conclusions: The results of the analysis indicated that the two equations using age, body weight, and the power output achieved at VO2 as predictor variables had the lowest SEE (7.7-9.8% of actual VO2max) and TE (10-12% of actual VO2max) values and are recommended for estimating VO2max in aerobically trained males and females. The magnitude of the TE values (>or= 20% of actual VO2max) associated with the remaining 16 equations, however, were too large to be of practical value for estimating VO2max.