Hormonal responses after a strength endurance resistance exercise protocol in young and elderly males.

This study examined testosterone, cortisol and growth hormone responses in elderly and young men after a strength endurance protocol. Eight elderly (age: 69 +/- 5 yrs) and nine young (age: 23 +/- 1 yrs) males with recreational experience in resistance training performed a strength endurance protocol, which included six exercises. At each exercise, the subjects performed 3 sets of 15 reps at 60 % of 1-RM with a 90 s rest interval between sets. The subjects also participated in a control session. Hormonal and blood lactate concentrations were measured before exercise, immediately after exercise and 15 min after the end of exercise. Blood lactate increased (p<0.05) with resistance exercise in both age groups with the highest increases observed in the young males. Testosterone and cortisol concentrations were higher (p<0.05) immediately and 15 min after exercise as compared to the respective control session values in both young and elderly subjects, whereas no differences were observed between groups (p>0.05). Growth hormone concentration increased (p<0.05) after resistance exercise compared to the control session in both age groups. This increase was higher (p<0.05) in the young as compared to the elderly group. The above results show that a moderate intensity - high repetition resistance exercise protocol for the improvement of strength endurance, seems to be a sufficient stimulus that increases testosterone, growth hormone and cortisol concentrations in elderly males. These hormonal responses may create an optimal metabolic environment, which improves muscular function after a strength endurance program although the elderly subjects present an attenuated growth hormone response compared to younger ones.

Failure to obtain a unique threshold on the blood lactate concentration curve during exercise.

The purpose of this study was to compare various methods and criteria used to identify the anaerobic threshold (AT), and to correlate the AT obtained with each other and with running performance. Furthermore, a number of additional points throughout the entire range of lactate concentrations [La-] were obtained and correlated with performance. A group of 19 runners [mean age 33.7 (SD 9.6) years, height 173 (SD 6.3) cm, body mass 68.3 (SD 5.4) kg, maximal O2 Uptake (VO2max) 55.2 (SD 5.9) ml x kg(-1) x min(-1)] performed a maximal multistage treadmill test (1 km x h[-1] every 3.5 min) with blood sampling at the end of each stage while running. All AT points selected (visual [La-], 4 mmol x l(-1) [La-], 1 mmol x l(-1) above baseline, log-log breakpoint, and 45 degrees tangent to the exponential regression) were highly correlated one with another and with performance (r > 0.90) even when there were many differences among the AT (P < 0.05). The additional points (ranging from 3 to 8 mmol x l(-1) [La-], 1 to 6 mmol x l(-1) [La-] above the baseline, and 30 to 70 degrees tangent to the exponential curve of [La-]) were also highly correlated with performance (r > 0.90). These results failed to demonstrate a distinct AT because many points of the curve provided similar information. Intercorrelations and correlations between AT and performance were, however, reduced when AT were expressed as the percentage of maximal treadmill speed obtained at AT or percentage of VO2max. This would indicate that different attributes of aerobic performance (i.e. maximal aerobic power, running economy and endurance) are measured when manipulating units. Thus, coaches should be aware of these results when they prescribe an intensity for training and concentrate more on the physiological consequences of a chosen [La-] rather than on a "threshold".