Influence of the duration of a treadmill walking bout on heart rate variability at rest in physically active women

Background: Heart rate variability (HRV) has been promoted as a noninvasive method of evaluating autonomic influence on cardiac rhythm. Although female subjects predominate in the walking studies, no study to date has examined the influence of the duration of a moderate intensity walking physical activity bout on HRV in this population. Methods: Twelve healthy physically active middle-aged women undertook 2 conditions; 20min (W20) and 60min (W60) bouts of walking on a treadmill. Resting HRV measures were obtained before (-1 h), and 1 h and 24 h after the walking bouts. Results: Mean NN interval (ie, normal-to-normal intervals between adjacent QRS complexes) was significantly lower (P = .017) at +1 h in W60 (832, 686-979ms) compared with W20 (889, 732-1046ms). A borderline main effect for time was observed for both the SDNN intervals in W60 (P = .056), and for low frequency (LF(abs)) power in W60 (P = .047), with post hoc tests revealing a significant increase between 1 h (51, 33-69 ms and 847, 461-1556 ms(2)) and +1 h (65, 34-97ms and 1316, 569-3042 ms(2)) for SDNN and LF(abs) power, respectively, but no increase at +24h compared with -1 h. Conclusions: It appears that a walking bout of 60 min duration does alter cardiac autonomic influence in healthy active women, and this alteration is not evident after 20 min of walking. Given the rather subtle effect, further studies with larger sample sizes are required to explore the nature of the changes in cardiac autonomic influence following a prolonged bout of walking

Objectively measured absolute and relative physical activity intensity levels in postmenopausal women

Objectives: To investigate how objectively measured physical activity (PA) levels differ according to absolute moderate intensity recommendation (3-6 METs) and relative to individual lactate thresholds (LT1 and LT2), and to verify if high-fit women record higher PA levels compared to women with lower aerobic fitness. Methods: Seventy-five postmenopausal women performed an incremental exercise test and several constant-velocity tests wearing an accelerometer to identify the activity counts (ct min-1) corresponding to LT1 and LT2. Individual linear regression determined activity counts cut-points for each intensity: (1) sedentary ( LT2). Participants then wore an accelerometer during a week to measure the time spent at each PA intensity level. Results: According to absolute intensity categorisation, high-fit postmenopausal women recorded twice as much time at moderate-to-vigorous PA (MVPA) (P < 0.01) than low-fit women. However, when PA intensity was calculated relative to individual lactate thresholds, MVPA was significantly reduced by half (P < 0.01) and the data revealed no differences (P = 0.62) between groups (∼20 min day-1 at MVPA). Conclusions: Accelerometer cut-points derived from absolute moderate-intensity recommendations overestimated MVPA. Similar time at MVPA was recorded by high- and low-fit postmenopausal women when the cut-points were tailored to individual lactate thresholds. A more accurate estimation of PA behaviour could be provided with the use of individually tailored accelerometer cut-points

Heart Rate Variability : Effect of Exercise Intensity on Postexercise Response

The purpose of the present study was to investigate the influence of two exercise intensities (moderate and severe) on heart rate variability (HRV) response in 16 runners 1 hr prior to (-1 hr) and at +1 hr, +24 hr, +48 hr, and +72 hr following each exercise session. Time domain indexes and a high frequency component showed a significant decrease (p < .001) between -1 hr and +1 hr for severe intensity. The low frequency component in normalized units significantly increased (p <.01) for severe intensity at +1 hr. Only severe exercise elicited a change in HRV outcomes postexercise, resulting in a reduction in the parasympathetic influence on the heart at +1 hr; however, values returned to baseline levels by +24 hr

VO2 Attained During Treadmill Running: The Influence of a Specialist (400-m or 800-m) Event

Purpose: Previously it has been observed that, in well-trained 800-m athletes, VO(2)max is not attained during middle-distance running events on a treadmill, even when a race-type pacing strategy is adopted. Therefore, the authors investigated whether specialization in a particular running distance (400-m or 800-m) influences the VO(2) attained during running on a treadmill. Methods: Six 400-m and six 800-m running specialists participated in the study. A 400-m trial and a progressive test to determine VO(2)max were completed in a counterbalanced order. Oxygen uptakes attained during the 400-m trial were compared to examine the influence of specialist event. Results: A VO(2) plateau was observed in all participants for the progressive test, demonstrating the attainment of VO(2)max. The VO(2)max values were 56.2 +/- 4.7 and 69.3 +/- 4.5 mL . kg(-1) min(-1) for the 400-m- and 800-m-event specialists, respectively (P = .0003). Durations for the 400-m trial were 55.1 +/- 4.2 s and 55.8 +/- 2.3 s for the 400-m- and 800-m-event specialists, respectively. The VO(2) responses achieved were 93.1% +/- 2.0% and 85.7% +/- 3.0% VO(2)max for the 400-m- and 800-m-event specialists, respectively (P = .001). Conclusions: These results demonstrate that specialist running events do appear to influence the percentage of VO(2)max achieved in the 400-m trial, with the 800-m specialists attaining a lower percentage of VO(2)max than the 400-m specialists. The 400-m specialists appear to compensate for a lower VO(2)max by attaining a higher percentage VO(2)max during a 400-m trial

Influence of test duration on oxygen uptake attained during treadmill running

Previous investigations have revealed that in well-trained middle-distance runners, oxygen uptake (VO2) does not attain maximal values (VO2max) in exhaustive treadmill trials where the VO2 demand exceeds VO2max. To date, this shortfall in the VO2 attained has been demonstrated in trials as short as 2 min in duration. In this study, we investigated whether a reduction in exhaustive test duration influences the VO2 attained during running on a treadmill. Six middle-distance runners participated in the study, completing an exhaustive 400 m and 800 m trial. These trials, together with a progressive test to determine VO2max, were completed in a counterbalanced order. Oxygen uptakes attained during the 400 m and 800 m trials were compared to examine the influence of exhaustive test duration. A plateau in VO2 was observed in all participants for the progressive test, demonstrating the attainment of VO2max. The mean speed, duration, and resulting distance in the constant-speed exhaustive trials were 25.8 km h(-1) (s=1.2), 55.8 s (s=2.3), and 400.2 m (s=20.2) for the 400 m trial, and 24.3 km h(-1) (s=0.8), 108.4 s (s=21.2), and 730.1 m (s=129.1) for the 800 m trial, respectively. A paired-samples t-test revealed a significantly different (P=0.018)%VO2max was attained for the 400 m (85.7%, s=3.0) and 800 m (89.1%, s=5.0) trials. In conclusion, VO2 did not reach VO2max during the exhaustive constant-speed 400 m and 800 m trials, but the test duration does influence the%VO2max achieved. Specifically, the VO2 attained becomes progressively further below VO2max as trial duration is reduced, such that 89% and 86% VO2max is achieved in exhaustive 800 m and 400 m constant-speed trials, respectively

Assessment of cardiovascular risk and vascular age in overweight/obese adults with primary hypertension:EXERDIET-HTA Study

Objectives: Hypertension (HTN), obesity and low cardiorespiratory fitness (CRF) are associated with an increased risk of a cardiovascular event. Taking part overweight/obese individuals with HTN the aims of the current study were: to estimate cardiovascular risk (CVR) and vascular age (VA) profiles analyzing potential sex differences; to determine whether VA is higher than chronological age (CA) and, whether CVR is associated with a low level of CRF. Methods: Overweight/obese non-Hispanic white participants (n=209; 141 men and 68 women) with primary HTN had their CVR and VA determined using the New Pooled Cohort Risk Equations and The Framingham method, respectively. Considering values of peak oxygen uptake, participants were divided into tertiles for each sex. Results: The CVR, but not VA (p=0.339), was higher (p<0.001) in men compared to women irrespective of age. Irrespective of sex VA was higher than CA (p<0.001). Age and body mass index were higher (p<0.05) in the low CRF group compared to other groups. There were no differences in CVR (p=0.907) and VA (p=1.643) when values were separated into CRF groups. Conclusions: Pooled Cohort Equations could underestimate the risk of suffering a cardiovascular event in the following 10 years in overweight/obese non-Hispanic white women with HTN compared to men. The VA appears to be a useful tool in communicating CVR in this population irrespective of sex. The CRF alone may not be enough to moderate the CVR

Effects of different aerobic exercise programmes with nutritional intervention in sedentary adults with overweight/obesity and hypertension: EXERDIET-HTA study

Background: Both exercise training and diet are recommended to prevent and control hypertension (HTN) and overweight/obesity. Purpose: To determine the effectiveness of different 16-week aerobic exercise programs with hypocaloric diet on blood pressure (BP), body composition, cardiorespiratory fitness (CRF) and pharmacological treatment. Methods: Overweight/obese, sedentary participants (n=175, 54.08.2 yrs) with HTN, were randomized into attention control group (AC, physical activity recommendations) or one of three supervised exercise groups [two days/week: high-volume with 45 min of moderate-intensity continuous training (HV-MICT), HV and high-intensity interval training, alternating high and moderate intensities (HV-HIIT), and low volume-HIIT (LVHIIT, 20 min)]. All variables were assessed pre and post intervention. All participants received the same hypocaloric diet. Results: Following the intervention, there was a significant reduction in BP and body mass in all groups with no between-group differences for BP. However, body mass was significantly less reduced in the AC group compared with all exercise groups (AC=-6.6%, HV-MICT=-8.3%, HV-HIIT=-9.7%, LV-HIIT=-6.9%). HIIT groups had significantly higher CRF than HV-MICT, but there were no significant between-HIIT differences (AC=16.4%, HV-MICT=23.6%, HV-HIIT=36.7%, LV-HIIT=30.5%). Medication was removed in 7.6% and reduced in 37.7% of the participants. Conclusions: The combination of hypocaloric diet with supervised aerobic exercise 2 days/week offers an optimal non-pharmacological tool in the management of BP, CRF and body composition in overweight/obese and sedentary individuals with HTN. HVHIIT seems to be better for reducing body mass compared to LV-HIIT. The exerciseinduced improvement in CRF is intensity dependent with LV-HIIT as a time-efficient method in this population

Effects of different aerobic exercise programs on cardiac autonomic modulation and hemodynamics in hypertension: data from EXERDIET-HTA randomized trial

The aims of the present study were to analyze the effects of 16 weeks of different aerobic exercise training (ExT) programs with diet on cardiac autonomic modulation and hemodynamics in non-physically active and overweight/obese adults (n=249, 53.7±8.0 years) with primary hypertension, and the possible differences among ExT programs and their effects on heart rate (HR), blood pressure (BP), and long-term BP variability (BPV). Participants were randomly assigned into an attention control (AC) group (physical activity recommendations) or one of three supervised ExT groups: high-volume of moderate-intensity continuous training, high-volume and high-intensity interval training (HIIT), and low volume-HIIT. 24 h ambulatory BP monitoring was used to analyze systolic and diastolic BP, HR and BPV. A cardiopulmonary exercise test was performed to determine peak oxygen uptake (VO2peak). Following intervention, resting and submaximal exercise (HR, SBP and DBP), along with diurnal and nocturnal SBP and DBP values decreased (P<0.05) in all groups with no differences between groups. When the ExT groups were combined, submaximal SBP (P=0.048) and DBP (P=0.004), VO2peak (P=0.014) and HR reserve (P=0.030) were significantly improved compared to AC. Intervention did not have significant effects on BPV. In the present study better improvements in the autonomic nervous system were seen when the aerobic ExT was individually designed and supervised with pari passu effects irrespective of exercise intensity and volume. Low volume-HIIT ExT combined with a healthy diet should be considered as a time efficient and safe mechanism for reducing the cardiovascular risk in hypertensive individuals

A metabolically healthy profile is a transient stage when exercise and diet is not supervised: long-term effects in the EXERDIET-HTA study

Metabolically unhealthy obesity (MUO) is a regular state in people with primary hypertension (HTN), obesity and physically inactive. To become and maintain a metabolically healthy overweight/obese (MHO) state should be a main treatment. The aims of the study were 1) to determine differences in metabolic profiles of overweight/obese, physically inactive individuals with HTN following a 16-week (POST) supervised aerobic exercise training (SupExT) intervention with an attentional control (AC) group and, 2) to determine whether the changes observed were maintained following six months (6M) of unsupervised time. Participants (n=219) were randomly assigned into AC or SupExT groups. All participants underwent a hypocaloric diet. At POST all participants received diet and physical activity advice for the following 6M, with no supervision. All measurements were assessed pre-intervention (PRE), POST, and after 6M. From PRE to POST, MUO participants became MHO with improved (P<0.05) total cholesterol (TC, ∆=-12.1 mg/dL), alanine aminotransferase ∆=-8.3 U/L), glucose (∆=-5.5 mg/dL), C-reactive protein (∆=-1.4 mg/dL), systolic blood pressure (SBP) and CRF compared to unhealthy optimal cut-off values. However, after 6M, TC, glucose, and SBP returned to unhealthy values (P<0.05). In a non-physically active population with obesity and HTN, a 16-week SupExT and diet intervention significantly improves cardiometabolic profile from MUO to MHO. However, after 6M of no supervision, participants returned to MUO. The findings of this study highlight the need for regular, systematic and supervised diet and exercise programs to avoid subsequent declines in cardiometabolic health

Is cardiorespiratory fitness independently associated with the biochemical profile in overweight/obese adults with primary hypertension? The EXERDIET-HTA study

Cardiorespiratory fitness (CRF) is positively associated with enhanced cardiovascular health. This cross-sectional study aimed to determine associations between CRF and the biochemical profile of overweight/obese adults diagnosed with primary hypertension (HTN). Does cardiorespiratory fitness (exposure) positively affect the biochemical profile (outcome) in overweight/obese individuals suffering from HTN? Assessment with anthropometric, ambulatory blood pressure monitoring (24 hours), CRF (peak oxygen uptake, V̇O2peak), and biochemical analysis was performed on 214 participants (138 men, 76 women). A series of linear and logistic regression analyses were conducted. Participants were divided into CRF tertiles (classified as low, moderate, and high CRF). The CRF was independently and inversely associated with aspartate aminotransferase (AST; β=-0.328, P<0.05) and alanine aminotransferase (ALT; β=-0.376, P<0.01) concentrations. C-reactive protein, AST/ALT ratio, gamma-glutamyl transpeptidase, total cholesterol/high-density lipoprotein cholesterol ratio, glucose, insulin and insulin resistance index (HOMA-IR), were all associated, but not independently, with CRF in linear and/or unadjusted logistic regression models. However, independently, logistic regression revealed that glucose was associated with the moderate CRF group. Findings suggest that a lower CRF is associated with an unhealthy biochemical profile in non-physically active and overweight/obese individuals with HTN. As such, this population should look to increase physical activity in order to improve their CRF and biochemical profile