Blunted cardiac autonomic dynamics to active standing test in postmenopausal women.

Introduction: Although both aging and menopause influence cardiovascular autonomic control, the effect of menopause per se remains unclear. The current study was undertaken to test the hypothesis that post-menopausal women (PMW) have a blunted cardiovascular autonomic adjustment to active standing compared to pre-menopausal women. Thus, we compared the heart rate variability (HRV) indexes from supine (SUP) to orthostatic (ORT) positions among young women (YW), young men (YM), older men (OM), and PMW. Methods: The participants rested for 10 min in SUP and then stood up and remained for 5 min in ORT. ECG was continuously recorded, and R-R time series of about 300 beats were analyzed using linear (spectral analysis) and non-linear (symbolic analysis) methods. The variation from SUP to ORT was calculated (Δ = ORT-SUP) for each HRV index. Results: In SUP, no difference was found for any HRV index among groups. However, Δ0V% and ΔLFn (cardiac sympathetic modulation) were reduced in PWM compared to all groups (OM, YW, and YM), while Δ2UV% and ΔHFn (cardiac vagal modulation) were reduced in PMW than the younger group (YW and YM). No differences were found among the male groups (OM and YM). Discussion: In light of our results, the cardiac autonomic dynamic response to orthostatic stress is blunted in post-menopausal women compared to younger women and older men, a finding that might be influenced not only by aging.

Heated environment offsets the cardiovascular responses to prolonged rowing exercise in competitive athletes.

Prolonged rowing exercise sessions are often prescribed considering competitive training schedules, and under hostile environments (e.g., heated ambient). The study aimed to investigate the effect of heat stress (HS) on physical performance, Lactate concentration ([Lac]), and cardiorespiratory responses during prolonged exercise sessions in competitive rowers. Twelve rowers performed preliminary exercise tests (2-km test and five-step incremental lactate test) to assess the target workload intensity corresponding to a 2.5 mmol.L-1 of [Lac]. On two separate days, participants were enrolled in two exercise sessions of 12 km in a rowing machine under HS (∼30 °C) and thermal comfort (TC 22 °C) conditions. Heart rate (HR), stroke volume (SV), cardiac output (CO), oxygen uptake (VO2), [Lac], and the rating of perceptual exertion (RPE) were obtained. From baseline, HS increased the maximum temperature of the face compared to TC. Workload and VO2 reduced while RPE increased at 9- and 12-km of rowing exercise under HS compared to TC. From baseline to the last stage of exercise, HS shifted SV downwards and HR upwards compared to TC. Consequently, CO did not change between thermal conditions (TC vs. HS). Therefore, HS provokes a cardiovascular drift during prolonged rowing in comparison to TC. The last stages of prolonged rowing sessions under HS seem to be critical to physical performance and relative perceptual of effort in rowers.

The Physical Capacity of Rowing Athletes Cannot Reverse the Influence of Age on Heart Rate Variability during Orthostatic Stress.

The current study was undertaken to test the hypothesis that the high physical capacity of rowing athletes may not reverse the influence of age on cardiac autonomic control decline estimated by heart rate variability (HRV). Forty-four male subjects divided in four groups: 11 young athletes (YA; 18 ±1 year), 11 young non-athletes (YNA; 20 ±1 year), 11 middle age athletes (MAA; 43 ±6 years) and 11 middle age non-athletes (MNA; 44 ±8 years) participated in the study. Heart rate (HR) was recorded beat-by-beat for 10 minutes in supine (SUP) and 10 min in orthostatic (ORT) positions. HRV was analyzed in the frequency domain to obtain the spectral power in the high (HF) and low frequency (LF) bands, and the changes to ORT (%∆HRV) were calculated (ORT - SUP / SUP). During SUP, HF was lower in MNA and MA compared to YA and YNA, while LF was lower in MNA than YA. For %ΔHRV, %ΔHF was higher in YA than YNA, MA and MNA. The %ΔLF was not different among groups. In conclusion, aging seems to overcome the influence of physical fitness on neural regulation of the heart, as highlighted by the HRV response to active standing.

Positive Pressure Ventilation Improves Exercise Performance and Attenuates the Fall of Postexercise Inspiratory Muscular Strength in Rower Athletes.

ABSTRACT: Gonçalves, TR and Soares, PP. Positive pressure ventilation improves exercise performance and attenuates the fall of postexercise inspiratory muscular strength in rower athletes. J Strength Cond Res 35(1): 253-259, 2021-Positive pressure ventilation (PPV) can increase exercise performance in cyclists, but its effects are unclear in other exercise modes, especially those using large muscle mass. The aim of this study was to compare the exercise performance and postexercise inspiratory muscles' strength with and without PPV (NO-PPV) during rowing. Nine male rowers (19 ± 1 year) participated in 3 experimental days (M1, M2, and M3) separated by 1 week. In M1, rowers performed a 2,000-m test (2k) on a rowing ergometer to obtain average power (W2k). In M2 and M3, the rowers performed 4 minutes' workouts at 55, 65, 75, and 85% W2k, respectively, separated by 1 minute of recovery, with PPV and NO-PPV application in randomized order. Blood lactate (La) was measured during intervals. After submaximal exercises, with 10 minutes of "cool down," the rowers performed a maximal performance test of 4 minutes (4-minute all-out rowing). Traveled distance was computed and correlated with maximal inspiratory pressure (MIP) changes from pretest to posttest (∆). Positive pressure ventilation application increased the traveled distance in relation to NO-PPV exercise (1,210.7 ± 45.5 vs. 1,199.8 ± 43.4 m, p ≤ 0.05). The ∆MIP (cmH2O) was lower in PPV as compared to NO-PPV exercise (-19.1 ± 10.2 vs. -26.3 ± 7.9 cmH2O, p ≤ 0.05). The [La] showed no significant difference between PPV and NO-PPV exercises (p > 0.05). Therefore, the PPV during whole-body rowing exercise improved the exercise performance and attenuated the inspiratory postexercise fatigue. These findings suggest that inspiratory muscles' strength plays a role during high-intensity exercise with large muscle mass.

Influence of breathing patterns and orthostatic stress on postural control in older adults.

AIM: To investigate the influence of breathing patterns and blood pressure behavior postural control in older adults. METHODS: A total of 20 older adults carried out spontaneous, controlled (15 cycles/min) and deep (6 cycles/min) breathing trials, in random order. In this session, the heart rate was recorded continuously and blood pressure measured every 3 min. In addition, the challenge from sitting to an active standing position was carried out with eyes closed during 6 min on a baropodometer plate with electromyography recording. The root mean square (RMS) of electromyography was calculated. RESULTS: There were significant differences in the postural control with spontaneous breathing from the first minute (center of pressure [COP]-area 216.40 ± 116.70 mm2 ) in comparison with the third minute (COP-area 79.35 ± 68.11 mm2 ; d = 0.89; P < 0.01) and the sixth minute (COP-area 70.24 ± 41.26 mm2 ; d = 0.60; P < 0.05) of active standing. Furthermore, deep breathing significantly increases the COP-area (158.50 ± 126.2 mm2 ) at the sixth minute of active standing in comparison with spontaneous breathing (70.24 ± 41.26 mm2 ; d = 0.80; P < 0.01). There were also significant differences in systolic blood pressure during spontaneous breathing between the baseline measures (sitting position 123 ± 11 mmHg) and the first minute of active standing (117 ± 13 mmHg; d = 0.24; P < 0.05). Furthermore, electromyography activity of the tibialis anterior increased during the deep (17.52 ± 9.21 RMS) and controlled breathing (16.75 ± 5.26 RMS) compared with the spontaneous condition (14.93 ± 5.56 RMS; d = 0.17; P < 0.05). CONCLUSIONS: The present data provide important insight into the respiratory and hemodynamics effects of postural control in older adults. The current data confirm that deep breathing causes periodic perturbation in the neuromuscular compensation of the lower limbs. Geriatr Gerontol Int 2018; 18: 692-697.