Effect of high-impact aerobics and strength training on BMD in young women aged 20-35 years.

To evaluate the effects of a 12-month exercise intervention using either high-impact step aerobic exercise or moderate-intensity strength training on areal bone mineral density (aBMD) we studied 51 untrained women, aged 20-35 years, for this study. Whole body and heel and wrist aBMD were measured by dual-energy X-ray absorptiometry (DXA, Hologic or PIXI Lunar). Subjects were randomly assigned to: impact-loaded step aerobic exercise (SA, n=15), moderate-intensity lower body strength training (ST, n=16) or non-exercise control (CON, n=20). Data analysis only included those who completed 95% of each training routine and attended at least 80% of all sessions. Group differences in aBMD, leg press strength and urinary cross-link deoxypridinoline (µDPD) were analysed using analysis of variance. After a 12-month intervention, the SA elicited an increase in aBMD of the heel (4.4%, p<0.05) and leg press strength (15%, p<0.05), relative to baseline. Meanwhile, the ST showed an increase in leg press strength (48%, p<0.05) with no significant increase in aBMD at any measured site. Similar and unchanged µDPD was observed in all 3 groups at baseline, 6 and 12 months. In conclusion, a 12-month high-impact step aerobic exercise resulted in a significant increase in the heel aBMD in untrained young women, who complied with the exercise regimen. A moderate intensity strength training intervention of similar duration had no effect on aBMD although leg strength increased significantly.

The role of the left temporal region under the cognitive motor demands of shooting in skilled marksmen.

A number of investigators have reported elevated left temporal alpha power in marksmen during response preparation. This finding has been interpreted to indicate the suppression of irrelevant cognitive processes. However, lower-order motor processes have not been excluded as a possible explanation. Event-related alpha power (11-13 Hz) was examined at sites T3, T4, C3, and C4 in eight skilled marksmen during shooting and two control tasks varying in perceptual-motor complexity. Over an 8-s period preceding the trigger pull, the marksmen exhibited higher power and slope at T3 than at all other sites during shooting compared with the control conditions. No such difference between conditions was detected at C3 and C4. The relative synchrony of left temporal alpha power during shooting, in conjunction with the lack of change at central sites, is inconsistent with the explanation that the effect is accounted for by 'lower-order' motor processes exclusively involving the central region.

Neuro-cognitive activity during a self-paced visuospatial task: comparative EEG profiles in marksmen and novice shooters.

Log-transformed EEG power spectral estimates (6-7, 9,10-11,18-22, and 36-44 Hz), obtained from skilled marksmen and novice shooters at sites F3, F4, C3, C4,T3, T4, P3, P4, O1, and O2 during the aiming period (6 s) of a target shooting task for each of 40 trials up to the moment of trigger pull, were contrasted to determine regional differences in cortical activation. The EEG power obtained from both groups during the preparatory aiming period was also compared to that observed for a similar time period during the processing of standard verbal and spatial tasks. The marksmen exhibited less activation than the novice shooters at all sites during the aiming period with a pronounced difference in the left central-temporal-parietal area. Fewer group differences in cortical activation were observed during the comparative verbal and spatial tasks with which the groups held equal experience. Additionally, the novice shooters exhibited a cortical activation pattern during target shooting that was similar to that observed during the processing of the comparative verbal and spatial tasks. In contrast, marksmen generally exhibited less cortical activation during the aiming period when contrasted to that during the novel comparative tasks. These results are consistent with the notion of relative economy in the cortical processes of marksmen, relative to controls, during the specific challenge with which they are highly practiced.

The effect of a psyching strategy on neuromuscular activation and force production in strength-trained men.

Force and electromyographic (EMG) activity of the biceps and triceps brachii were measured in 15 strength-trained men during maximal isometric action of the forearm flexors, with the elbow at 90 degrees, following 20-s periods of psyching (PSY), reading aloud (RA), and mental arithmetic (MA). Perceived arousal and attentional focus ratings for PSY were greater than those obtained for RA and MA, which were undifferentiated. Perceived effort, biceps and triceps EMG, and maximal force did not differ across conditions. Therefore, in highly trained men under conditions of brief exertion, when the biomechanics of the muscular action were controlled, psyching resulted in a perception of enhanced readiness but did not influence force or muscular activation differently from psychological states that were preceded by distraction.

Vagal and cardiac reactivity to psychological stressors in trained and untrained men.

PURPOSE: The aim of this study was to determine whether higher aerobic fitness is associated with enhanced vagal influences on the myocardium, resulting in moderation of chronotropic cardiac activity during psychological stress and recovery. METHOD: Heart period (HP) and respiratory sinus arrhythmia (RSA) were obtained from 10 aerobically trained (AT) and 10 untrained (UT) college-aged men at rest and during three contiguous psychological challenges and 3 min of recovery. Ratings of perceived stress were obtained at the end of the rest period, at the midpoint of each stressor, and at 30 s into recovery. Time series methods were used to quantify RSA from the beat-to-beat HP series. Responsivity was assessed both in terms of absolute levels of activity and phasic changes in activity (task or recovery minus baseline). RESULTS: Both groups reported similar levels of subjective stress throughout the experiment. The AT exhibited longer HP at rest and during psychological stress and recovery than did the UT. However, the groups did not differ on RSA at rest or during psychological stress and recovery, nor did they differ on phasic changes in RSA or HP during stress or recovery. Additionally, aerobic capacity was not correlated with absolute levels or phasic changes in RSA during psychological challenge for either group and, except in Min 2 for the UT, similar results were obtained for recovery. CONCLUSIONS: The results supported the hypothesis that, among young men, higher aerobic fitness is associated with longer HP at rest and during psychological stress and recovery. However, the lower cardiac chronotropic activation observed among the AT relative to the UT was not paralleled by a group difference in the amplitude of RSA. These results suggest that the group difference in HP was not mediated directly by the vagal mechanisms manifested in the amplitude of RSA.

Respiratory sinus arrhythmia during exercise in aerobically trained and untrained men.

Respiratory sinus arrhythmia (RSA) was examined in aerobically trained (AT) and untrained (NT) college-aged males during 12 periods consisting of a 3-min sitting baseline, six common 3-min absolute exercise stages, and five 3-min recovery stages that followed voluntary exhaustion to determine the relationship of work and training status to parasympathetic influence upon the heart. RSA systematically decreased during absolute exercise, was observed at heart rates (HR) above 100 beats x min(-1), and progressively increased during recovery. Additionally, independent of work stages, comparative regression analyses were conducted for both the exercise and recovery phases, separately, in which HR was regressed on RSA, as well as RSA on % VO2max, to contrast the obtained relationships for the AT and NT. No differences were revealed as a function of endurance training status as the slopes and intercepts obtained for the two groups from each of these analyses were similar. The within-subject correlations between RSA and % VO2max, calculated for each of the individuals across all 12 periods, were consistently negative. Between-subjects correlations of RSA with RR and tidal volume were predominantly nonsignificant, indicating that RSA, as measured here, is independent of individual differences in ventilatory activity and, as such, can be compared between groups during exercise. The findings demonstrate that RSA is detectable during both exercise and recovery, even at HR beyond 100 beats x min(-1), and reveals a similar relationship to HR and metabolic state in both aerobically trained and untrained populations.

The effect of psychological strategies upon cardiorespiratory and muscular activity during treadmill running.

Twelve aerobically trained males (age 22 +/- 1.3 yr, range 18-31) were studied to determine the effects of VE and EMG feedback upon cardiorespiratory and muscular activity during one segment of a continuous 36-min bout of treadmill running just below ventilatory threshold (VT). Ventilatory, metabolic, cardiovascular, RPE, and EMG variables recorded during a 12-min feedback segment were compared with those observed during 12-min attentional distraction and control conditions. The three treatments were counterbalanced. Mean VO2 (2987 ml.min-1) remained constant across the three periods as did VCO2 (3102 ml.min-1), HR (168 bpm), RQ (0.95), and O2 pulse (18.5 ml.beat-1). However, VE was significantly reduced during feedback (Fb) as compared with both the distraction (D) and control (C) conditions (mean +/- SE: 83.2 +/- 3.6 vs 86.6 +/- 4.2 and 87.8 +/- 4.2 l.min-1, respectively). This effect was marked by a reduction in respiratory rate (RR) (41.1 +/- 2.1 vs 44.5 +/- 1.9 and 46.8 +/- 1.9 breaths.min-1 for Fb, D, and C, respectively) and an increase in tidal volume (TV) (2115 +/- 144 vs 1904 +/- 110 and 2020 +/- 102 ml.breath-1 for Fb, D, and C, respectively). These changes resulted in significant reductions in VE/VO2 (26.5 +/- 0.7 vs 28.9 +/- 1.0 and 28.3 +/- 0.9 ratio magnitudes), VE/VO2 (28.1 +/- 0.8 vs 30.2 +/- 1.0 and 29.7 +/- 1.0 ratio magnitudes), and PETO2 (105.5 +/- 1.0 vs 108.4 +/- 1.1 and 107.6 +/- 1.2 mm Hg) during Fb as compared with D and C, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)