The effects of a plyometric training program on the latency time of the quadriceps femoris and gastrocnemius short-latency responses.

AIM: The purpose of this study was to determine if a plyometric training program can affect the latency time of the quadriceps femoris and gastrocnemius short-latency responses (SLRs) of the stretch reflex. METHODS: Sixteen healthy subjects (12 female and 4 male) were randomly assigned to either a control or a plyometric training group. Maximum vertical jump height (VJ) and SLRs of both quadriceps femoris and gastrocnemius were measured before and after a four week plyometric training program. RESULTS: Plyometric training significantly increased VJ (mean+/-SEM) by 2.38+/-0.45 cm (P<0.05) and non-significantly decreased the latency time of the quadriceps femoris SLR (mean+/-SEM) 0.363+/-0.404 ms (P>0.05) and gastrocnemius SLR (mean+/-SEM) 0.392+/-0.257 ms (P>0.05). VJ results support the effectiveness of plyometric training for increasing VJ height. CONCLUSIONS: The non-significant changes in the latency time of the quadriceps femoris and gastrocnemius SLRs seen in the training group suggest that performance improvements following a four-week plyometric training program are not mediated by changes in the latency time of the short-latency stretch reflex.

The relationship between field tests of anaerobic power and 10-km run performance.

The purpose of this study was to investigate the relationship between several field tests of anaerobic power and distance running performance. Thirty-six trained runners (20 men and 16 women; mean +/- SD age, 27.9 +/- 5.7 years) participated in this study. Tests of anaerobic power consisted of a 50-m sprint, vertical jumps from a static take-off position and with a countermovement, a plyometric leap test, and a 300-m sprint. The results indicated that gender, height, weight, percent body fat, 50-m sprint time, the height and power of both types of vertical jumps, plyometric leap distance, and the 300-m sprint time were significantly correlated with 10-km run time (p < or = 0.05) in the total subject pool (N = 36). Stepwise multiple regression identified the plyometric leap distance to explain 73.9% of the variance in run time. When combined with 300-m sprint time, 77.9% of the variance (standard error of the estimate, 2.92 minutes) was explained. The regression equation developed is Y' (10-km time) = 57.22 - 5.15(plyometric leap distance in meters) + 0.27(300-m sprint time in seconds). The results indicate that anaerobic power is significantly related to distance running performance and may explain a meaningful percentage of variability in 10-km run time. Therefore, it may be beneficial for distance runners to supplement aerobic training with some power and speed development such as plyometrics and sprinting.

Comparison of active and passive recovery of blood lactate and subsequent performance of repeated work bouts in ice hockey players.

This study examined the effect of active and passive recovery on lactate concentration and subsequent performance of repeated work bouts in 18 male NCAA Division I ice hockey players. Using a repeated measures design, subjects performed a series of skating tests before and after a 15-minute recovery. The skating test consisted of skating a course for 7 shifts, which lasted 40 seconds per shift with 90 seconds rest between shifts. Active recovery (low-intensity cycling) and passive recovery (sitting) lasted for 15 minutes and were followed by an identical 7-shift skating test. Passive vs. active recovery showed no statistically significant differences for distance skated, heart rate, or lactate. There appeared to be a trend for greater skating distance in period 2 when active recovery was used, but the difference was not significant (p > 0.05). It was concluded that active recovery did not enhance lactate removal or subsequent performance of repeated work bouts in simulated hockey play.

The accuracy of the ACSM stair-stepping equation.

PURPOSE: The purpose of this study was to determine the accuracy of the ACSM equation used to estimate the oxygen cost of stepping exercise. The equation appears as: VO2 (mL.kg(-1).min(-1)) = 0.2 (steps.min(-1)) + (step height, m x steps.min(-1) x 2.4) + 3.5. METHODS: Subjects were 55 men and women between the ages of 19 and 35 yr. Steady-state VO2 was measured at six different combinations of step heights and step rates. Step heights were 0.1, 0.2, and 0.3 m (4, 8, and 12 in, respectively) and step rates were 20 and 25 steps.min(-1). Predicted VO2 for each workload was derived from the ACSM equation. RESULTS: Mean differences between actual and predicted VO2 values ranged from -0.2 to -1.1 mL.kg(-1).min(-1) and was -0.6 mL.kg(-1).min(-1) for all workloads combined. All differences except the lowest were significant (P < or = 0.05). Total errors ranged from 1.3 to 2.5 mL.kg(-1).min(-1) and was 1.9 mL.kg(-1).min(-1) for all workloads combined. For all workloads combined, the correlation between actual and predicted VO2 was r = 0.95 with a SEE = 1.7 mL.kg(-1).min(-1). The statistics are comparable to other ACSM prediction equations. CONCLUSION: Although all of the mean differences except one were statistically significant, they were judged negligible from a practical standpoint. Therefore, it was concluded that the ACSM equation is an accurate predictor of the oxygen cost of stair-stepping exercise.

Relationship of somatotype and physical characteristics to distance running performance in middle age runners.

BACKGROUND: The purpose of this study was to determine the variance explained by somatotype, selected anthropometric variables, and muscle cross-sectional area (CSA) on 10 km run time. METHODS: Subjects were 19 female and 34 male moderately trained distance runners who competed in a local 10 km road race. Mean ages were 39.7 +/- 9.2 for females and 42.7 +/- 10.3 yr for males. RESULTS: Endomorphy explained 41.0% (R = 0.64, SEE = 6.5 min) of the variance in females' 10 km time, whereas body mass index explained 28.0% (R = 0.53, SEE = 7.8 min) with mesomorphy adding 10.4% (R = 0.62, SEE = 7.3 min) more explained variance in males' running times. With data combined for men and women, endomorphy explained 22.1% (R = 0.47, SEE = 7.9 min) of the variance. CONCLUSIONS: It was concluded that somatotype and body mass index explain a moderate portion of the variance in 10 km run performance in runners heterogeneous in ability. Muscle and muscle plus bone cross-sectional area of related running muscles does not contribute to the explained variance in men. Research seeking to explain sources of variation in running performance should consider including somatotype as an independent variable.

Affective responses of physically active and sedentary individuals during and after moderate aerobic exercise.

BACKGROUND: This study examined the effects of aerobic fitness and exercise history on self-reported affect during and after acute aerobic exercise and quite reading. METHODS: Active and sedentary participants (N = 41) reported their psychological affect during two separate conditions in a counterbalanced design: (1) exercise on a cycle ergometer at 50% predicted VO2 max, and (2) quiet reading in a reclining chair. Affect was assessed prior to, every 3 minutes during, and at 5 and 20 minutes after each 24-minute exercise and reading period. RESULTS: Analysis revealed that active participants were significantly more positive than the sedentary group during exercise and at 5 minutes postexercise. The groups were similar in affect at 20 minutes postexercise. No between-group differences were found during the reading condition. Exercise enhanced affect compared to reading only for the active group. In addition, the affective responses of both groups were influenced by pre-exercise affect, with the greatest increases observed for those reporting the lowest affect before activity. CONCLUSIONS: These results suggest that affective responses during and after aerobic exercise were influenced by exercise history and aerobic fitness, but moderated by pre-activity scores.

Validity of bioelectrical impedance analysis to measure body fat in Air Force members.

This study determined if the bioelectrical impedance analysis (BIA) method was a more valid assessment of body fat in Air Force members than the current Air Force circumference (AF) method. Both methods were compared with hydrostatic weighing, which is the presumed standard for identifying body fat. Subjects included 50 male and 50 female active duty Air Force members between the ages of 19 and 47 years. The AF method had higher correlation coefficients and lower standard error of estimates for both male and female subjects (r = 0.91 [3.00%] and r = 0.79 [3.28%], respectively) than the BIA method (r = 0.84 [3.25%] and r = 0.75 [4.30%], respectively). The false-positive rates for individuals having excess body fat were greater for the AF method (14.7 and 29.3% for males and females, respectively) than the BIA method (7.3 and 8.8% for males and females, respectively). The data suggest that caution should be used when the current AF method or the BIA method is used to make individual Air Force career decisions.

Ankle injuries and ankle strength, flexibility, and proprioception in college basketball players.

OBJECTIVE: To determine if ankle muscular strength, flexibility and proprioception can predict ankle injury in college basketball players and to compare ankle injury rates in female and male players. DESIGN AND SETTING: In this prospective, correlational study, subjects were tested at the start of the competitive season for ankle joint muscle strength, flexibility, and proprioception. The first ankle injury for each subject was recorded on an injury report form, and the data were analyzed to determine if any of these preseason measurements predicted future injury. The setting was a competitive 9-week season for four women's and four men's college basketball teams. SUBJECTS: A convenience sample of 31 female and 11 male college basketball players. MEASUREMENTS: Subjects were tested for ankle dorsiflexion range of motion, various measures of ankle proprioception, and isokinetic peak torque of ankle dorsiflexion-plantar flexion and eversion-inversion at 30 degrees /sec and 180 degrees /sec before the start of the conference basketball seasons. Data were analyzed using a series of multiple regression equations to determine the variance in ankle injury attributed to each variable. RESULTS: Various measures of proprioception predicted left ankle injury in all subjects (p < .05), while ankle strength and flexibility measures failed to account for additional variance. There was no statistically significant difference in ankle injury rate between women and men. CONCLUSIONS: Ankle joint proprioceptive deficits can be used to predict ankle injury, but further research is needed to identify other sources of variance. In our study, ankle injury rate was similar in female and male college basketball players.

The accuracy of the ACSM and a new cycle ergometry equation for young women.

The purpose of this study was to determine the accuracy of the American College of Sports Medicine's (ACSM) equation for estimating the oxygen cost of exercise performed by women on a cycle ergometer. Sixty healthy, young females performed a five-stage submaximal cycle ergometry test. Results indicated the SEE for the predicted oxygen values ranged from 79-156 ml.min-1, with total errors (E) ranging from 107-275 ml.min-1. Correlations between the actual and predicted values ranged from r = -0.22 to r = 0.38. The r, SEE, and E were 0.96, 118, and 172, respectively for all of the power loads combined. A revised equation was developed based upon the actual VO2-power relationship. This equation appears as: VO2 (ml.min-1) = kgm.min-1 x 1.6 ml.min-1 + ((3.5 ml.kg-1.min-1 x kg body weight) + 205 ml.min-1). Cross validation was performed on an independent sample of 40 subjects. All of the SEE and E were lower and all of the correlations were higher at each power load in the validation sample. Since the revised equation is based on an actual VO2-power relationship, it would appear that it provides a more accurate depiction of the cycle ergometry VO2-power relationship for women. These facts support its use.

Validation of a cycle ergometry equation for predicting steady-rate VO2.

The purpose of this study was to validate an equation used for predicting the oxygen cost of leg cycle ergometry. This equation was previously shown to be more accurate than the one of the American College of Sports Medicine (ACSM) and appears as: VO2 (ml.min-1) = kgm.min-1 x 1.9 ml.min-1 + ((3.5 ml.kg-1.min-1 x kg body weight) + 260 ml.min-1). Fifty healthy males, ages 18-38 yr old, performed a six-stage (0, 180, 360, 540, 720, and 900 kgm.min-1) submaximal cycle ergometry test while their oxygen uptake was measured. Results indicated the standard error of estimate for the predicted oxygen consumption values ranged from 80-156 ml.min-1, with correlations between the actual and predicted values ranging from r = 0.35 to r = 0.67. Total errors ranged from 92-160 ml.min-1. All of the standard errors and total errors were lower and all of the correlations, except one, were higher at each power load in the validation sample than the original sample. These statistics support the generalizability and accuracy of the new equation. It would appear that the new equation may make accurate predictions in independent samples and is more precise than the ACSM equation.