Exercise for fitness does not decrease the muscular inactivity time during normal daily life.

The time spent in sedentary behaviors has been shown to be independent of exercise in epidemiological studies. We examined within an individual whether exercise alters the time of muscular inactivity within his/her normal daily life. Quadriceps and hamstring muscle electromyographic activities and heart rate were measured during 1 to 6 days of normal daily living of ordinary people. Of 84 volunteers measured, 27 (15 men, 12 women, 40.7 years ± 16.5 years) fulfilled the criteria of having at least 1 day with and 1 day without exercise for fitness (total of 87 days analyzed, 13.0 h ± 2.5 h/day). Reported exercises varied from Nordic walking to strength training and ball games lasting 30 min-150 min (mean 83 min ± 30 min). Exercise increased the time spent at moderate-to-vigorous muscle activity (6% ± 4% to 9% ± 6%, P < 0.01) and energy expenditure (13% ± 22%, P < 0.05). Muscular inactivity, defined individually below that measured during standing, comprised 72% ± 12% of day without and 68% ± 13% of day with exercise (not significant). Duration of exercise correlated positively to the increase in moderate-to-vigorous muscle activity time (r = 0.312, P < 0.05) but not with inactivity time. In conclusion, exercise for fitness, regardless of its duration, does not decrease the inactivity time during normal daily life. This is possible by slight modifications in daily nonexercise activities.

Resistance exercise-induced hormonal response under the influence of delayed onset muscle soreness in men and boys.

It was hypothesized that exercise-induced muscle damage (EIMD)-related alterations in hormonal responses could be observed if a second exercise bout is performed soon after an identical unaccustomed bout leading to delayed onset muscle soreness (DOMS). Eight men (31 ± 7 years) and eight boys (14 ± 0 years) performed two exercise bouts (E1 and E2, with 48 h rest in between) consisting of three sets of bilateral knee extensions until exhaustion with 40% load. No differences between the groups or bouts were observed in the number of repetitions performed and maximal isometric force decline, or between groups in serum creatine kinase activity and DOMS. Decreased peak epinephrine (EPI) (-38%), growth hormone (GH) (-45%) and cortisol (COR) (-31%) concentrations were found in E2 in men (P<0.05). In men, the peak GH concentration was also lower in E2 and COR was higher in both bouts than in boys. No changes in norepinephrine and testosterone responses were found in either group. The results suggest that in men, the responses of EPI, GH and COR are attenuated when the second bout is performed under the influence of DOMS. In boys, the lack of this attenuation may not be explained by less severe EIMD.

Effects of marathon running on running economy and kinematics.

The present study was designed to investigate interactions between running economy and mechanics before, during, and after an individually run marathon. Seven experienced triathletes performed a 5-min submaximal running test on a treadmill at an individual constant marathon speed. Heart rate was monitored and the expired respiratory gas was analyzed. Blood samples were drawn to analyze serum creatine kinase activity (S-CK), skeletal troponin I (sTnI), and blood lactate (B-La). A video analysis was performed (200 frames x s(-1)) to investigate running mechanics. A kinematic arm was used to determine the external work of each subject. The results of the present study demonstrate that after the marathon, a standardized 5-min submaximal running test resulted in an increase in oxygen consumption, ventilation, and heart rate (P < 0.05), with a simultaneous decrease in the oxygen difference (%) between inspired and expired air, and respiratory exchange ratio (P < 0.05). B-La did not change during the marathon, while sTnI and S-CK values increased (P < 0.05), peaking 2 h and 2 days after the marathon, respectively. With regard to the running kinematics, a minor increase in stride frequency and a similar decrease in stride length were observed (P < 0.01). These results demonstrate clearly that weakened running economy cannot be explained by changes in running mechanics. Therefore, it is suggested that the increased physiological loading is due to several mechanisms: increased utilization of fat as an energy substrate, increased demands of body temperature regulation, and possible muscle damage.

Plasma catecholamine responses and neural adaptation during short-term resistance training.

Low exercise-induced plasma adrenaline (A) responses have been reported in resistance-trained individuals. In the study reported here, we investigated the interaction between strength gain and neural adaptation of the muscles, and the plasma A response in eight healthy men during a short-term resistance-training period. The subjects performed 5 resistance exercises (E1-E5), consisting of 6 sets of 12 bilateral leg extensions performed at a 50% load, and with 2 days rest in between. Average electromyographic (EMG) signal amplitude was recorded before and after the exercises, from the knee extensor muscles in isometric maximal voluntary contraction (MVC) as well as during the exercises (aEMGmax and aEMGexerc, respectively). Total oxygen consumed during the exercises (VO2tot) was also measured. All of the exercises were exhaustive and caused significant decreases in MVC (34-36%, P < 0.001). As expected, the concentric one-repetition maximum (1-RM), MVC and aEMGmax were all higher before the last exercise (E5) than before the first exercise (E1; 7, 9 and 19%, respectively, P < 0.05). In addition, in E5 the aEMGexerc:load and VO2tot:load ratios were lower than in E1 (-5 and -14%, P < 0.05), indicating enhanced efficiency of the muscle contractions, However, the post-exercise plasma noradrenaline (NA) and A were not different in these two exercises [mean (SD) 10.2 (3.8) nmol x l(-1) vs 11.3 (6.0) nmol x l(-1), ns, and 1.2 (1.0) nmol x l(-1) vs 1.9 (1.1) nmol x l(-1), ns, respectively]. However, although NA increased similarly in every exercise (P < 0.01), the increase in A reached the level of statistical significance only in E1 (P < 0.05). The post-exercise A was also already lower in E2 [0.7 (0.7) nmol x l(-1), P < 0.05) than in E1, despite the higher post-exercise blood lactate concentration than in the other exercises [9.4 (1.1) mmol x l(-1), P < 0.05]. Thus, the results suggest that the observed attenuation in the A response can not be explained by reduced exercise-induced strain due to the strength gain and neural adaptation of the muscles. Correlation analysis actually revealed that those individuals who had the highest strength gain during the training period even tended to have an increased post-exercise A concentration in the last exercise as compared to first one (r = 0.76, P < 0.05).

Plasma catecholamine responses to four resistance exercise tests in men and women.

The plasma adrenaline ([A]) and noradrenaline ([NA]) concentration responses of nine men and eight women were investigated in four resistance exercise tests (E80, E60, E40 and E20), in which the subjects had to perform a maximal number of bilateral knee extension-flexion movements at a given cycle pace of 0.5 Hz, but at different load levels (80%, 60%, 40% and 20% of 1 repetition maximum, respectively). The four test sessions were separated by a minimal interval of 3 rest days. The number of repetitions (Repmax), the total work (Wtot) done normalized for the lean body mass and the heart rate (HR) responses were similar in the two groups in each test. In addition, no differences were found between the two groups in [A] and [NA] either before or after the exercise tests. The postexercise [NA], both in the men [10.8 (SD 7.0) nmol x l(-1)] and in the women [11.7 (SD 7.4) nmol x l(-1)], was clearly the highest in E20, where also the Repmax, WtOt, the total amount of integrated electromyograph activity in the agonist muscles and the peak postexercise blood lactate concentration [men 8.3 (SD 1.6) vs women 7.3 (SD 0.9) mmol x l(-1), ns] were significantly higher than in the other tests. Although the postexercise [A] in E20 both in the men [7.1 (SD 6.0) nmol x l(-1)] and in the women [5.2 (SD 2.0) nmol x l(-1)] were higher than in E80 [men 3.1 (SD 4.2), women 2.1 (SD 2.0) nmol x l(-l)] (P < 0.05), they were not significantly different from E60 [men 3.6 (SD 1.9), women 4.0 (SD 3.3) nmol x l(-1)] and E40 [men 3.8 (SD 4.1), women 5.8 (SD 4.0) nmol x l(-1)] in either group. The present study did not indicate any sex differences in performance and in plasma catecholamine responses in different exhausting resistance exercise tests performed with the knee extensor muscles. In both groups the plasma [NA] response was clearly the largest in the longest exercise with the greatest amount of muscle activity and work done, and with the largest blood lactate response. The differences in the plasma [A] responses between the exercises tended to be somewhat smaller.

Plasma catecholamine and serum testosterone responses to four units of resistance exercise in young and adult male athletes.

The plasma noradrenaline (NA) and adrenaline (A) concentration responses of seven young male athletes [15 (SD 1) years] and seven adult male athletes [25 (SD 6) years] were investigated together with the serum testosterone (Tes) concentration responses in four different half-squatting exercises. The loads, number of repetitions, exercise intensity and recovery between the sets were manipulated such that different types of metabolic demand could be expected. However, the amount of work done was kept equal in each kind of exercise. After the most exhausting unit of exercise (E3; two sets of 30 repetitions with 50% of 1 repetition maximum and with 2-min recovery between the sets) the plasma NA concentration was significantly lower in the younger than in the adult subjects [15.7 (SD 7.8) vs 32.7 (SD 13.2) nmol x l(-1), P < 0.05], while the A concentrations were similar. In the other three exercises no differences in the plasma catecholamine concentration responses among the groups were observed. The postexercise Tes concentrations, however, were significantly lower in the younger than in the adult subjects in every exercise unit. No correlations between the plasma catecholamine and serum Tes concentration responses were observed in any of the exercise units in either group. The results of the present study may suggest reduced sympathetic nervous activity in the younger subjects compared to the adults in response to exhausting resistance exercise. The results may also suggest that the catecholamines were less involved in eliciting an increase in Tes secretion in these resistance exercises.

Blood lactate and ammonia in short-term anaerobic work following induced alkalosis.

This study was designed to investigate the effect of an induced metabolic alkalosis on a 300 m sprinting time in six elite 400 m runners. The subjects competed as pairs, on two separate occasions, in a standard racing format, three hours after ingestion of either an alkaline (sodium citrate, 0.5 g.kg-1 body weight) or a placebo solution (calcium carbonate, 0.5 g.kg-1 body weight). The results showed that following alkaline ingestion mean sprinting time was not improved. Peak blood lactate during recovery was higher after sodium citrate administration than after placebo (19.88 +/- 2.09 vs 18.82 +/- 1.84 mmol.l-1, p < 0.01). No difference was observed in peak blood ammonia between the alkaline and placebo treatments (187.0 +/- 37.0 vs 188.8 +/- 49.0 mumol.l-1). The absence of effects on performance confirms that when exercise of short duration (30 to 40 s) is used, alkaline agents have minor or no effects on performance. The altered relationship observed between blood lactate and ammonia under placebo and buffering loading conditions suggests that the regulation of lactate and ammonia metabolism is unrelated.

Aerobic characteristics, oxygen debt and blood lactate in speed endurance athletes during training.

Aerobic characteristics, oxygen debt and blood lactate were analysed in 20 male speed endurance athletes (400 m sprinters and 400 m hurdlers). The subjects were tested three times; at the beginning of March, at the end of May and at the end of August. Aerobic and anaerobic threshold and maximal oxygen uptake measured on the treadmill decreased (p < 0.05-0.01) from the second test occasion to the third one. The anaerobic work test on the treadmill was a constant load test at 5.56 m.s-1 with a slope of 4 degrees. The time to exhaustion increased (p < 0.05) from the first test occasion (112 +/- 17 s) to the second one (136 +/- 35 s) and did not change in the last test (135 +/- 25 s). Following the anaerobic work test oxygen debt was measured during 20 minutes. The highest total oxygen debt values (144 +/- 19 ml.kg-1) were observed in the second test occasion. Peak blood lactate following the anaerobic work increased (p < 0.05) from the first test occasion to the second one and remained at the same level during the next three competitive months. The good speed endurance athletes differed from the poor counterparts in time to exhaustion (p < 0.01), in 100 m record time (p < 0.01) and in maximal oxygen uptake (p < 0.05). Our results suggest that aerobic characteristics decrease during the competitive period in speed endurance athletes. The anaerobic performance capacity including work time and peak blood lactate is at high level in the competitive period.(ABSTRACT TRUNCATED AT 250 WORDS)