Repeated change-of-direction test for collegiate male soccer players.

AIM: The aim of the study was to investigate the applicability of a repeated change-of-direction (RCoD) test for NCAA Division-I male soccer players. METHODS: The RCoD test consisted of 5 diagonal direction changes per repetition with a soccer ball to be struck at the end. Each player performed 15 repetitions with approximately 10 seconds to jog back between repetitions. Data were collected in two sessions. In the first session, 13 players were examined for heart rate responses and blood lactate concentrations. In the second session, 22 players were examined for the test's ability to discriminate the primary from secondary players (78.0±16.1 and 10.4±13.3 minutes per match, respectively). RESULTS: Heart rate data were available only from 9 players due to artifacts. The peak heart rate (200.2±6.6 beats∙min-1: 99.9±3.0% maximum) and blood lactate concentration (14.8±2.4 mmol∙L-1 immediately after) resulted in approximately 3.5 and 6.4-fold increases from the resting values, respectively. These values appear comparable to those during intense periods of soccer matches. In addition, the average repetition time of the test was found to discriminate the primary (4.85±0.23 s) from the secondary players (5.10±0.24 s) (P=0.02). CONCLUSION: The RCoD test appears to induce physiological responses similar to intense periods of soccer matches with respect to heart rate and blood lactate concentration. Players with better average repetition times tend to be those who play major minutes.

Bone mineral density and content of collegiate throwers: influence of maximum strength.

AIM: Bone changes in size and density in response to different levels of stress. Alterations to bone mineral density (BMD) appear to occur in a site specific manner. Even though BMD has been examined in many populations there is a paucity of data looking at strength-power athletes, such as throwers. Therefore, the purpose of this study was to examine the BMD of a group of USA Division I collegiate throwers (e.g. shot put, discus, etc.). METHODS: Seven throwers (4 males; 3 females) who were 19.0 + or - 0.9 years had their BMD compared to an age matched control group (n = 14; 8 women and 6 men) and normative data. BMD was measured with dual X-ray absorptometry. Potential right/left side and sex difference in BMD were also examined. Maximal isometric strength was assessed using a mid-thigh pull while standing on a forceplate which generated force-time curves. Peak force (PF) and normalized peak force (PFa) were then correlated with BMDs. RESULTS: Generally, throwers had denser bones with male throwers tending to have a greater total BMD (P < or = 0.05). The dominant arm BMD was slightly greater when compared to non-dominant arm (P < or = 0.05). Furthermore, total body BMD was related to PF (r = 0.68, r(2) = 0.46) and PFa (r = 0.56, r(2) = 0.31). CONCLUSIONS: Throwers have greater BMDs than non-athletes and most other athletes. However, throwers only showed a small indication of sidedness. It is likely that the BMDs observed in this study stem from the training intervention (e.g. whole body heavy lifting) undertaken by this population.

The effects of supplemental carbohydrate ingestion on intermittent isokinetic leg exercise.

BACKGROUND: The purpose of this investigation was to examine the effects of carbohydrate (CHO) supplementation on isokinetic leg extension/flexion exercise performance, blood glucose responses, blood free fatty acid (FFA) responses, and blood lactate (La) responses. METHODS: Eight resistance trained males (mean+/-SEM, age: 23.7+/-1.3 yrs, height: 180.0+/-3.5 cm, bodymass: 94.9+/-4.9 kg) participated in a randomized, double blind protocol with testing sessions separated by 7-d. Subjects were given CHO or placebo (P) while performing 16 sets of 10 repetitions at 120 degrees x s(-1) on a Cybex isokinetic dynamometer. Performance variables measured were; total work (TW), average work (AW), peak torque (PT) and average torque (AT). Plasma glucose (PG), FFA, and La were measured prior to testing (PRE), after set 8 (MID), and 16 (POST). RESULTS: Results indicated that the CHO treatment elicited significantly (p<0.05) more TW (CHO: 41.1+/-3.9 kJ; P: 38.1+/-3.9 kJ) and AW (CHO: 2.6+/-0.2 kJ; P: 2.4+/-0.2 kJ). There were no differences (p<0.05) between treatments for PT of the hamstrings (CHO: 91.6+/-6.5 Nm; P: 87.4+/-8.5 Nm) and quadriceps (CHO: 129.7+/-9.5 Nm; P: 123.0+/-10.6 Nm). The AT of the hamstrings (CHO: 77.8+/-5.2 Nm; P: 75.7+/-8.7 Nm) and quadriceps (CHO: 116.9+/-8.9 Nm; P: 110.0+/-8.5 Nm) were not statistically different (p>0.05) between the treatments. PG was significantly higher at the POST blood draw in the CHO treatment. No significant differences (p>0.05) were observed between the treatments for FFA and La concentrations. CONCLUSIONS: The data from this investigation indicate that the use of CHO supplementation during isokinetic leg exercise allows for the performance of more work.

Carbohydrate supplementation attenuates muscle glycogen loss during acute bouts of resistance exercise.

The effects of carbohydrate (CHO) supplementation on muscle glycogen and resistance exercise performance were examined with eight highly resistance trained males (mean +/- SEM, age: 24.3 +/- 1.1 years, height: 171.9 +/- 2.0 cm, body mass: 85.7 +/- 3.5 kg; experience 9.9 +/- 2.0 years). Subjects participated in a randomized, double blind protocol with testing sessions separated by 7 days. Testing consisted of an initial isokinetic leg exercise before and after an isotonic resistance exercise (IRT) session consisting of 3 leg exercises lasting approximately 39 min. Subjects consumed a CHO (1.0 g CHO.kg body mass(-1)) or placebo treatment (PLC), prior to and every 10-min (0.5 g CHO.kg body mass(-1)) during the IRT. Muscle tissue was obtained from the m vastus lateralis after a supine rest (REST) immediately after the initial isokinetic test (POST-ISO) and immediately after the IRT (POST-IRT). The CHO treatment elicited significantly less muscle glycogen degradation from the POST-ISO to POST-IRT (126.9 +/- 6.5 to 109.7 +/- 7.1 mmol.kg wet weight(-1)) compared to PLC (121.4 +/- 8.1 to 88.3 +/- 6. 0 mmol.kg wet weight(-1)). There were no differences in isokinetic performance between the treatments. The results of this investigation indicate that the consumption of a CHO beverage can attenuate the decrease in muscle glycogen associated with isotonic resistance exercise but does not enhance the performance of isokinetic leg exercise.

Training status influences T-cell responses in women following acute resistance exercise.

The purpose of this investigation was to examine white blood cell counts (WBC), immunoglobulin (IgA, IgG, IgM) levels, and T-cell proliferation following acute resistance training in 9 untrained (UT) and 6 trained (TR) women. Resistance training on 7 Universal machines at the subject's 10 repetition maximum (IORM) was performed at 89 +/- 5% for UT and 88 +/- 3% for TR. Blood was analyzed for WBCs and Ig levels pre-exercise, immediately postexercise, and 1.5, 3, and 24 hours postexercise. T-cell proliferation was determined pre-exercise and 3 hours postexercise through response to phytohemagglutanin (PHA). WBCs were significantly elevated in the UT subjects 1.5 and 3 hours postexercise compared with pre- and immediately postexercise; no differences (p < 0.05) were observed in TR subjects. No significant differences were found for Ig levels either between or within groups, although there was a trend for decreased IgG following exercise. T-cell proliferation was significantly decreased in the UT at 3 hours postexercise (0.27 +/- 0.06 units) compared with pre-exercise (0.41 +/- 0.06 units), whereas the proliferative response in TR was not significantly different from pre-exercise (0.48 +/- 0.04 units) to 3 hours postexercise (0.34 +/- 0.06 units). These data indicate that UT subjects experience an increase in WBC counts and a decrease in T-cell proliferative ability after acute resistance training, whereas TR subjects experience no significant change in these parameters.