To study the physiologic basis of variability of physical performance in the laboratory, ten male subjects were studied once a week, during a 9-12 month period. Previously, the reference maximal work load attained (Wref) was determined in each subject. The test protocol of the actual study was based on the individual Wref and started at 70% Wref for 5 min whereupon the work load was increased by 5% Wref every 2.5 min to exhaustion. The maximal work load attained (Wmax) was considered as the test performance. Heart rate, respiratory variables, oxygen uptake (VO2), and blood lactate concentration were determined at each work load. The rate of perceived exertion during submaximal and maximal work was also scored. In all subjects, Wmax and VO2max varied randomly, while the coefficient of variation in VO2max (4.20% - 11.35%) exceeded that in Wmax (2.95%-6.83%). No seasonal influences on VO2 max and Wmax were observed. In all subjects the physiologic variables, when plotted as a function of external work load, were shifted to the right with higher Wmax values and to the left with lower Wmax values. With lower Wmax values, the rate of perceived exertion during submaximal work tended to increase. The results suggest that the magnitude of physiologic responses to exercise is related to relative work load and that variability of physical performance is related to changes in gross mechanical efficiency.

This study examined the effect of 12 weeks of exercise training on daily physical activity in elderly humans. Training consisted of a weekly group session and an individual session with cardio- and weight-stack machines. A group of 15 subjects served as the exercise group [EXER mean age 59 (SD 4) years], and 7 subjects as the controls [CONT mean age 57 (SD 3) years]. Physical activity and physical fitness were measured before the start of training (T), at week 6 and week 12 (T0, T6, T12 respectively) in EXER, and at T0 and T12 in CONT. Physical activity over 14 days was measured using a tri-axial accelerometer and physical fitness was measured during an incremental exercise test. At T12, mean maximal power output had significantly increased in EXER compared to CONT 8 (SD 12) vs -5 (SD 9) W; P < 0.02] and mean submaximal heart rate (at 100 W) had reduced [-10 (SD 7) vs -2 (SD 6) beats x min(-1); P < 0.05]. No differences or changes in physical activity were observed between EXER and CONT. At T6, physical activity on training days was significantly higher than on non-training days (P < 0.001). When the accelerometer output of the training session was subtracted from the accelerometer output on training days, at T12 non-training physical activity was significantly lower than on non-training days (P < 0.004). Accelerometer output of the individual training session at T12 had significantly increased compared to T6 (P < 0.05), whereas, accelerometer output of the group training session had remained unchanged. In conclusion, in elderly subjects an exercise training programme of moderate intensity resulted in an improved physical fitness but had no effect on total daily physical activity. Training activity was compensated for by a decrease in non-training physical activity.

To study the occurrence of running-related injuries, a group of 115 volunteers were supervised in a training program. These subjects who had limited or no running experience were asked to keep a diary in which they registered information on the training program and injuries. Ultimately, 63% of the diaries fulfilled the criteria for inclusion into longitudinal analysis. The training program (18-20 months) consisted of three phases, each phase finished with a contest (15 km, 25 km, and a marathon, respectively). The participants were individually supervised by an experienced coach with special attention to physiologic training and injury-preventive aspects. Eighty-five percent (n = 62) of the research population sustained at least one injury during the experiment. They reported in total 174 injuries. The number of injury cases per week increased gradually over the experimental period; however, when expressed per unit of exposure time (i.e., 1000 training hours), it showed a decline. There was a significant correlation between the number of injured volunteers and the distance covered during the training at the start of the training program. The anatomic distribution of the injuries is in agreement with findings in the literature. There was also a possible preference for the localization of injuries to the lower leg and Achilles tendon on the left side of the body.

Van Etten, Ludo M. L. A., Klaas R. Westerterp, Frans T. J. Verstappen, Bart J. B. Boon, and Wim H. M. Saris. Effect of an 18-wk weight-training program on energy expenditure and physical activity. J. Appl. Physiol. 82(1): 298–304, 1997.—The purpose of this study was to examine the effect of an 18-wk weight-training program on average daily metabolic rate (ADMR). Before the intervention and in weeks 8 and 18(T0, T8, and T18, respectively) data on body composition, sleeping metabolic rate (SMR), food intake, energy cost of the weight-training program (EEex), and nontraining physical activity (accelerometer) were collected in the exercise group (EXER, n = 18 males). ADMR was determined in a subgroup (EX12, n = 12) by using doubly labeled water. At T0 and T18, data (except ADMR) were also collected in a control group (Con, n = 8). Body mass did not change in EXER or Con. Fat-free mass increased only in EXER with 2.1 ± 1.2 kg, whereas fat mass decreased in EXER as well as Con (2.0 ± 1.8 and 1.4 ± 1.0 kg, respectively). Initial ADMR (12.4 ± 1.2 MJ/day) increased at T8 (13.5 ± 1.3 MJ/day, P < 0.001) with no further increase at T18 (13.5 ± 1.9 MJ/day). SMR did not change in EXER (4.8 ± 0.5, 4.9 ± 0.5, 4.8 ± 0.5 kJ/min) or Con (4.7 ± 0.4, 4.8 ± 0.4 kJ/min). Energy intake did not change in EXER (10.1 ± 1.8, 9.7 ± 1.8, 9.2 ± 1.9 MJ/day) or Con (10.2 ± 2.6, 9.4 ± 1.8, 10.1 ± 1.5 MJ/day) and was systematically underreported in EX12 (−21 ± 14, −28 ± 18, −34 ± 14%, P < 0.001). EEex (0.47 ± 0.20, 0.50 ± 0.18 MJ/day) could only explain 40% of the increase in ADMR. Nontraining physical activity did not change in both groups. In conclusion, although of modest energy cost, weight-training induces a significant increase in ADMR.

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