Strength training combined with plyometric jumps in adults: sex differences in fat-bone axis adaptations.

Leptin and osteocalcin play a role in the regulation of the fat-bone axis and may be altered by exercise. To determine whether osteocalcin reduces fat mass in humans fed ad libitum and if there is a sex dimorphism in the serum osteocalcin and leptin responses to strength training, we studied 43 male (age 23.9 2.4 yr, mean +/- SD) and 23 female physical education students (age 23.2 +/- 2.7 yr). Subjects were randomly assigned to two groups: training (TG) and control (CG). TG followed a strength combined with plyometric jumps training program during 9 wk, whereas the CG did not train. Physical fitness, body composition (dual-energy X-ray absorptiometry), and serum concentrations of hormones were determined pre- and posttraining. In the whole group of subjects (pretraining), the serum concentration of osteocalcin was positively correlated (r = 0.29-0.42, P < 0.05) with whole body and regional bone mineral content, lean mass, dynamic strength, and serum-free testosterone concentration (r = 0.32). However, osteocalcin was negatively correlated with leptin concentration (r = -0.37), fat mass (r = -0.31), and the percent body fat (r = -0.44). Both sexes experienced similar relative improvements in performance, lean mass (+4-5%), and whole body (+0.78%) and lumbar spine bone mineral content (+1.2-2%) with training. Serum osteocalcin concentration was increased after training by 45 and 27% in men and women, respectively (P < 0.05). Fat mass was not altered by training. Vastus lateralis type II MHC composition at the start of the training program predicted 25% of the osteocalcin increase after training. Serum leptin concentration was reduced with training in women. In summary, while the relative effects of strength training plus plyometric jumps in performance, muscle hypertrophy, and osteogenesis are similar in men and women, serum leptin concentration is reduced only in women. The osteocalcin response to strength training is, in part, modulated by the muscle phenotype (MHC isoform composition). Despite the increase in osteocalcin, fat mass was not reduced.

Serum free testosterone, leptin and soluble leptin receptor changes in a 6-week strength-training programme.

Strength training is usually associated with a reduction in fat mass and with muscle hypertrophy. The aim of the present study was to examine whether the serum free leptin index (FLI), measured by the molar excess of soluble leptin receptor (sOB-R) over leptin, is increased by 6 weeks of strength training. Eighteen male, physical education students were randomly assigned to two groups: a strength-training (n 12) and a control group (n 6). Body composition (lean body mass and body fat) determined by dual-energy X-ray absorptiometry (DXA), muscle performance and leptin, sOB-R, total testosterone and free testosterone concentrations were determined before and after training. Fat mass was reduced by 1 kg with strength training (P<0.05). Lean body mass of trained extremities was increased by 3% (P<0.05), while the concentration of free testosterone in serum was reduced by 17% (P<0.05) after training. However, despite the reduction in fat mass and free testosterone, serum leptin concentration was not significantly affected by strength training, even after accounting for the differences in body fat. By contrast, for a given fat mass, the sOB-R was increased by 13% (P<0.05) at the end of the strength-training programme, although the molar excess of sOB-R over leptin remained unchanged. Therefore, the quantity of free leptin available to bind to the target tissues was not significantly affected by the short strength-training programme, which elicited a 7% reduction in fat mass.

Anaerobic energy provision does not limit Wingate exercise performance in endurance-trained cyclists.

The aim of this study was to evaluate the effects of severe acute hypoxia on exercise performance and metabolism during 30-s Wingate tests. Five endurance- (E) and five sprint- (S) trained track cyclists from the Spanish National Team performed 30-s Wingate tests in normoxia and hypoxia (inspired O(2) fraction = 0.10). Oxygen deficit was estimated from submaximal cycling economy tests by use of a nonlinear model. E cyclists showed higher maximal O(2) uptake than S (72 +/- 1 and 62 +/- 2 ml x kg(-1) x min(-1), P < 0.05). S cyclists achieved higher peak and mean power output, and 33% larger oxygen deficit than E (P < 0.05). During the Wingate test in normoxia, S relied more on anaerobic energy sources than E (P < 0.05); however, S showed a larger fatigue index in both conditions (P < 0.05). Compared with normoxia, hypoxia lowered O(2) uptake by 16% in E and S (P < 0.05). Peak power output, fatigue index, and exercise femoral vein blood lactate concentration were not altered by hypoxia in any group. Endurance cyclists, unlike S, maintained their mean power output in hypoxia by increasing their anaerobic energy production, as shown by 7% greater oxygen deficit and 11% higher postexercise lactate concentration. In conclusion, performance during 30-s Wingate tests in severe acute hypoxia is maintained or barely reduced owing to the enhancement of the anaerobic energy release. The effect of severe acute hypoxia on supramaximal exercise performance depends on training background.

Running economy and delayed onset muscle soreness.

BACKGROUND: The main purpose of this study was to test the effects of a duathlon competition on running economy. METHODS. EXPERIMENTAL DESIGN: A prospective study. SETTING: University. PARTICIPANTS: nine male and six female physical education students, which mean (SEM) age was 24.0 (1.3) years. MEASURES: Subjects participated in two competitive duathlons: D1 and D2 (5 km running + 16 km cycling + 2 km running). Before D1, an incremental exercise test on the treadmill was performed to determine the V O2max, the running speed at exhaustion (vmax), and the V O2, as well as the running speed (u) attained at the first and second ventilatory threshold (V O2V T1, uV T1, V O2V T2, uV T2). Two days later running economy (RE1) was assessed at four different speeds corresponding to 58, 63, 67 and 71% of the umax. During the following six weeks the subjects trained 4 days a week, running all them 210 km in total. At the end of the training program the incremental exercise test and the duathlon competition were repeated (D2). Two and seven days after the second duathlon running economy was measured again (RE2 and RE3, respectively). RESULTS: Small, but significant improvements were observed in duathlon performance, V O2max, umax, uV T1, V O2V T2 and uV T2, after training. Two days after D2 the oxygen cost of running was approximately 5% higher than seven days after D2 (p < 0.001). The respiratory exchange ratio increased by approximately 0.04 units between RE2 and RE3 (p < 0.001). However, the increase in fat oxidation in RE2 only accounted for approximately 20% of the extra oxygen cost of running (RE2 vs RE3). No significant differences across tests were observed for ventilation (V E), heart rate, V CO2 and V E/V CO2. CONCLUSIONS: This study shows that two days after a duathlon competition running economy is impaired, however, seven days after the competition the oxygen cost of running is restored.

Reliability of jumping performance in active men and women under different stretch loading conditions.

BACKGROUND: To determine the reliability of squatting jumps (SJ), counter-movement jumps (CMJ) and drop jumps (DJ) tests, as well as the reliability of the optimal dropping height during drop jumping. METHODS: Jumping performance was assessed in 8 male and 9 female physical education students. Their age, weight and height (mean +/- SD) were 23.9 +/- 2.1 years, 72.0 +/- 12.1 kg, 174.3 +/- 10.4 cm, and 23.1 +/- 2.0 years, 54.8 +/- 4.9 kg, 160.1 +/- 5.0 cm for the males and females, respectively. The jumping performance was determined on six different testing days. On each testing day, squatting jumps (SJ) and counter-movement jumps (CMJ) were performed as well as drop jumps (DJ) from heights between 20 and 100 cm. The dropping height given the maximum attained height was registered as the optimal dropping height (ODH). After a 15 min rest period, a 30 sec hopping test (HT) was performed and the mean height attained (MHT) as well as the number of jumps executed (NHT) were recorded. The height attained was computed from the flight time, which was measured with a digital timer (+/- 0.001 sec) connected to a resistive platform. RESULTS: The pooled coefficients of variation in percentage were 5.4 (SJ), 6.3 (CMJ), 6.2 (DJ), 31.9 (ODH), 3.1 (NHT) and 6.7 (MHT). A parabolic relationship between dropping height and attained height was found (r = 0.39-0.43, p < 0.001). The ODH was 48.2 +/- 14.0 cm and 62.9 +/- 21.3 cm for females and males, respectively (p < 0.05). Multiple regression analysis showed than ODH can be predicted from the SJ with a standard error of 9 cm. CONCLUSIONS: The variability of the assessment of jumping performance is similar to that reported for other variables used in the assessment of physical fitness. In contrast, the assessment of the optimal dropping height is less reliable.

Cycling efficiency and pedalling frequency in road cyclists.

The purpose of this study was to determine the influence of pedalling rate on cycling efficiency in road cyclists. Seven competitive road cyclists participated in the study. Four separate experimental sessions were used to determine oxygen uptake (VO(2)) and carbon dioxide output (VCO(2)) at six exercise intensities that elicited a VO(2) equivalent to 54, 63, 73, 80, 87 and 93% of maximum VO(2) (VO(2max)). Exercise intensities were administered in random order, separated by rest periods of 3-5 min; four pedalling frequencies (60, 80, 100 and 120 rpm) were randomly tested per intensity. The oxygen cost of cycling was always lower when the exercise was performed at 60 rpm. At each exercise intensity, VO(2) showed a parabolic dependence on pedalling rate (r = 0.99-1, all P < 0.01) with a curvature that flattened as intensity increased. Likewise, the relationship between power output and gross efficiency (GE) was also best fitted to a parabola (r = 0.94-1, all P < 0.05). Regardless of pedalling rate, GE improved with increasing exercise intensity (P < 0.001). Conversely, GE worsened with pedalling rate (P < 0.001). Interestingly, the effect of pedalling cadence on GE decreased as a linear function of power output (r = 0.98, n = 6, P < 0.001). Similar delta efficiency (DE) values were obtained regardless of pedalling rate [21.5 (0.8), 22.3 (1.2), 22.6 (0.6) and 23.9 (1.0)%, for the 60, 80, 100 and 120 rpm, mean (SEM) respectively]. However, in contrast to GE, DE increased as a linear function of pedalling rate (r = 0.98, P < 0.05). The rate at which pulmonary ventilation increased was accentuated for the highest pedalling rate (P < 0.05), even after accounting for differences in exercise intensity and VO(2) (P < 0.05). Pedalling rate per se did not have any influence on heart rate which, in turn, increased linearly with VO(2). These results may help us to understand why competitive cyclists often pedal at cadences of 90-105 rpm to sustain a high power output during prolonged exercise.

Fractional use of anaerobic capacity during a 30- and a 45-s Wingate test.

This study examined the suitability of the Wingate test as a means of assessing the maximal oxygen deficit (MOD), and the influence of the anaerobic capacity on the fraction of the MOD used during a 30- and a 45-s Wingate test in 19 male subjects. The MOD incurred in constant-intensity supramaximal exercise was higher (P < 0.01) than that for the 45-s and 30-s Wingate tests [68.6 (3.4) vs 60.9 (2.2) and 53.7 (1.6) ml x kg(-1), respectively], corresponding to a 10% higher value for the 45-s compared to that for the 30-s test (P < 0.001). A close correlation was found to occur between MOD and the oxygen deficit incurred during the 30- and 45-s Wingate tests, as well as between both all-out tests (r = 0.86-0.90; P < 0.001). The oxygen deficit accumulated during the first 30 s of the 45-s Wingate test was similar to that accumulated during the 30-s Wingate test. The intraclass correlation coefficient for the oxygen deficit after 30 s of all-out exercise (two treatments) was 0.96. The higher the MOD the lower was its fractional recruitment during the 30-s (r = -0.88, P < 0.001) and during the 45-s (r = -0.74, P < 0.01) Wingate tests. In conclusion, 80-90% as an assessment of the oxygen deficit incurred during a Wingate test is valid as an estimate of the anaerobic capacity. The fraction of the anaerobic capacity used in a 30- and 45-s all-out test is inversely related to the anaerobic capacity.