Eccentric and concentric strength of the shoulder and arm musculature in collegiate baseball pitchers.

Many pitching injuries occur during deceleration of the upper extremity when the muscles of the shoulder and arm are acting eccentrically. Published information regarding eccentric muscular strength in baseball pitchers is nonexistent. The purpose of this study was to assess bilateral isokinetic eccentric and concentric muscular strength of the shoulder's external and internal rotator muscles and the elbow's flexor and extensor muscles in a group of collegiate baseball pitchers (N = 25). Isokinetic strength was assessed at 1.6, 3.7, and 5.2 rad/sec. Our findings indicate that the internal rotator muscles were always stronger than the external rotator muscles and that the concentric and eccentric external-to-internal strength ratios ranged from 62% to 81%. The eccentric strength of the shoulder rotator muscles averaged 114% that of concentric strength. The concentric and eccentric elbow extension-to-flexion strength ratios ranged from 71% to 110%; eccentric strength averaged 33% higher than concentric strength. No differences were noted between dominant and nondominant limbs for any of the strength measures or ratios. Clinically, the findings of this study can serve as a reference during the evaluation, rehabilitation, and conditioning of throwing athletes.

Recovery of dynamic muscle function following isokinetic fatigue testing.

This study was designed to evaluate recovery of dynamic muscle function following muscle fatigue produced by isokinetic testing. Sixteen physically active males (age = 29.2) performed fatigue and recovery tests on an isokinetic dynamometer (KIN-COM 500H). The fatigue test involved concentric contractions of the quadriceps femoris performed until force output fell below 50% MVC for 3 consecutive contractions. This test was repeated 3 times, with 1 minute rest between sets. Recovery of force output was measured during the following 8 minutes. Following post hoc analysis, subjects were grouped into 1 of 3 groups based on their time to recovery of 80% MCV; Recovery immediately following fatigue exercise (Group 1), between 3 and 6 minutes (Group 2), or no recovery during the 8 minute period (Group 3). Analysis revealed a significant decline in peak force between bouts of a three-bout fatigue test for Groups 2 and 3 (p < 0.001), and no decline in Group 1. There was a significant relationship between decline in force output and time to recovery. Thus, subjects developing a greater amount of muscle fatigue took longer to recover following this isokinetic test. It was concluded that an isokinetic fatigue test to 50% MVC, repeated 3 times, is an appropriate fatigue generating protocol for most active males; that recovery time following isokinetic fatigue exercise varies among active males; and recovery may be directly related to decline in force output between bouts of a three-bout fatigue test.

Efficacy of a home-based training program for older adults using elastic tubing.

The purpose of this study was to investigate the efficacy of, and the adherence to, a 12-week home-based progressive resistance training program for older adults utilizing elastic tubing. Sixty-two adults (mean age, 71.2 years) qualified to participate in the study. Subjects were randomly assigned to either the exercise (E) (n = 31) or non-exercise (NE) group (n = 31). Pre- and post-testing included isokinetic (1.05 rad.s-1) concentric/eccentric knee extension/flexion strength testing and flexibility measures of the hip, knee, and ankle. The E group trained three times per week, performing one to three sets of 10-12 repetitions for each of 12 resistance exercises. The exercises involved muscles of both the lower and upper body. Within the E group, 25 of the 31 subjects (80.6%) completed the study. Of the E subjects completing the study adherence to the three training sessions per week was 90% (range 72%-100%). Training resistances used during workouts increased significantly with the average estimated increase being 82% (P < 0.001). The E group also demonstrated significant (P < 0.05) increases in isokinetic eccentric knee extension (12%) and flexion (10%) strength. No other significant changes were observed between E and NE groups. These results suggest that home-based resistance training programs utilizing elastic tubing can serve as a practical and effective means of eliciting strength gains in adults over the age of 65.

Interpreting the relationship between age of menarche and prepubertal training.

It has been concluded from studies using retrospective data and thus quasi-experimental designs that menarche may be delayed by prepubertal athletic training. Furthermore, a causal relationship between the age of initiation of training (AIT) and the age of menarche (AOM) has been proposed. To investigate the possibility that these conclusions were erroneous and based upon analytical artifact, a computer program was used to generate random and independent AOM and AIT for a population of 30,000 "athletes". The generated mean AOM (means = 13.4 yr) and mean AIT (means = 10.0 yr) were similar to those reported in recent literature. The sampling procedure was designed such that no relationship existed between AOM and AIT in these hypothetical athletes (r = 0.002). When two subgroups (pre- or post-menarcheal training) were compared, the pre-training group was found to have a significantly later AOM than the post-trained group (means = 13.9 yr vs means = 11.7 yr; P less than 0.05). Significant correlations were found for each subgroup between AOM and AIT (r = 0.46 and 0.40 pre- and post-menarcheal training, respectively), similar to values previously reported. In conclusion, the sampling procedures performed in the present study and in similar data sets result in biased estimates of the statistical parameters. This bias accounts for the reported relationship between AOM and AIT derived using this type of quasi-experimental design, and therefore it would appear appropriate to state that the age of menarche in athletes is "later" rather than "delayed".