The relationship between the percentage of heart rate reserve (%HRR) and percentage of oxygen uptake reserve (%VO
2
R) has been recommended for prescribing aerobic exercise intensity. However, this ...relationship was derived from progressive maximal exercise testing data, and the stability of the relationship during prolonged exercise at a constant work rate has not been established. The main aim of this study was to investigate the stability of the %VO
2
R–%HRR relationship during prolonged treadmill exercise bouts performed at 3 different constant work rates. Twenty-eight men performed 4 exercise tests: (i) a ramp-incremental maximal exercise test to determine maximal heart rate (HR
max
) and maximal oxygen uptake (VO
2max
) and (ii) three 40-min exercise bouts at 60%, 70%, and 80% VO
2
R. HR and VO
2
significantly increased over time and were influenced by exercise intensity (p < 0.001 and p = 0.004, respectively). A 1:1 relationship between %HRR and %VO
2
R, and between %HRR and %VO
2max
, was not observed, with mean differences of 8% (t = 5.2, p < 0.001) and 6% (t = 4.8, p < 0.001), respectively. The VO
2
values predicted from the ACSM running equation were all significantly higher than the observed VO
2
values (p < 0.001 for all comparisons), whereas a difference for HR was observed only for the tenth min of exercise at 80% VO
2
R (p = 0.041). In conclusion, the main finding of this study was that the %HRR–%VO
2
R relationship determined by linear regression, obtained from progressive maximal exercise testing, did not apply to prolonged treadmill running performed at 3 work rates.
Abstract The physical activity readiness questionnaire (PAR-Q) has been the most popular simple method of screening for people who intend to engage in exercise programs. Despite of the ...recommendations indicating that the instrument should be applied in the age range from 15 to 69 years, the questionnaire has been widely used in elderly people. The aim of this study was to assess the diagnostic accuracy of PAR-Q in elderly women with respect to absolute and relative contraindications to exercise and verify the influence of educational level and cognitive status. Eighty-nine subjects (61–89 years) participated in the study and went through clinical exams and exercise testing. The influence of educational status, age and cognitive state (Mini-Mental State Examination, MMSE) on the PAR-Q responses was analyzed by logistic regression. The occurrences of absolute and relative contraindications were respectively 9% and 22%. The Sensitivity and Specificity were 75.0% and 19.8% (absolute) and 77.8% and 19.7% (relative). The PAR-Q results were not influenced by low educational status; age, or cognitive state. In conclusion, although the usefulness and easy applicability of the PAR-Q's questions, the responses to the questionnaire led to a high number of false positive and false negative cases, suggesting that it would not be adequate as a pre-participation screening tool in elder samples.
This study investigated the relationship between oxygen uptake (VO
2
), cardiac output (Q), stroke volume (SV), and heart rate (HR) in 54 men and 77 women (age = 69 ± 5 years) during incremental ...effort. Subjects performed a maximal cycle-ergometer test and VO
2
was directly measured. HR and SV were assessed by ECG and cardiograph impedance. Regression equations were calculated for Q–VO
2
, HR–VO
2
, and Q–HR relationships. The equations obtained for women were (a) Q (l min
−1
) = 2.61 + 4.67 VO
2
(l min
−1
)(
r
2
= 0.84); (b) HR (bpm) = 62.03 + 46.55 VO
2
(l min
−1
) (
r
2
= 0.72); (c)
(
r
2
= 0.41); (d) HR (bpm) = 41.48 + 9.24 Q (l min
−1
) (
r
2
= 0.73). Equations for men were (a) Q (l min
−1
) = 2.52 + 5.70 VO
2
(l min
−1
) (
r
2
= 0.89); (b) HR (bpm) = 66.31 + 32.35 VO
2
(l min
−1
) (
r
2
= 0.72); (c)
(
r
2
= 0.47); (d) HR (bpm) = 56.33 + 5.25 Q (l min
−1
) (
r
2
= 0.69). The intercepts for Q–VO
2
and HR–VO
2
equations were similar for both genders, but the slopes were different (
P
< 0.05). The SV increased from baseline to 50–60% of VO
2
peak in both groups. No gender effect was found in SV increasing pattern, but the absolute values were in general higher for men (
P
> 0.05). A significant difference between men and women was observed for both slopes and intercepts in the Q–HR relationship (
P
< 0.05). In conclusion, (a) Q–VO
2
relation was linear during progressive effort; (b) regression intercepts were similar, but the slopes were higher for men compared to women; (c) SV–VO
2
relationship was nonlinear and maximum SV was reached at very submaximal workload; (d) older men exhibited higher Q upward potential as well higher SV but lower HR for a given submaximal workload than women of similar age.
Systemic and central cardiovascular adaptations may vary in response to chronic exercise performed with different intensities and volumes. This study compared the effects of aerobic training with ...different intensities but equivalent volume upon microvascular reactivity in cremaster muscle and myocardial biomarkers of oxidative stress in Wistar rats. After peak oxygen uptake (VO2peak) assessment, rats (n = 24) were assigned into three groups: moderate-intensity exercise training (MI); high-intensity exercise training (HI); sedentary control (SC). Treadmill training occurred during 4 weeks, with exercise bouts matched by the energy expenditure (3.0-3.5 Kcal). Microvascular reactivity was assessed in vivo by intravital microscopy in cremaster muscle arterioles, while biomarkers of oxidative stress and eNOS expression were quantified at left ventricle and at aorta, respectively. Similar increasing vs. sedentary control group (SC) occurred in moderate intensity training group (MI) and high-intensity training group (HI) for endothelium-dependent vasodilation (10-4M: MI: 168.7%, HI: 164.6% vs. SC: 146.6%, P = 0.0004). Superoxide dismutase (SOD) (HI: 0.13 U/mg vs. MI: 0.09 U/mg and SC: 0.06 U/mg; P = 0.02), glutathione peroxidase (GPX) (HI: 0.00038 U/mg vs. MI: 0.00034 U/mg and SC: 0.00024 U/mg; P = 0.04), and carbonyl protein content (HI: 0.04 U/mg vs. MI: 0.03 U/mg and SC: 0.01 U/mg; P = 0.003) increased only in HI. No difference across groups was detected for catalase (CAT) (P = 0.12), Thiobarbituric acid reactive substances (TBARS) (P = 0.38) or eNOS expression in aorta (P = 0.44). In conclusion, higher exercise intensity induced greater improvements in myocardium antioxidant defenses, while gains in microvascular reactivity appeared to rely more on exercise volume than intensity.
ABSTRACTGonçalves, TR, Farinatti, PTV, Gurgel, JL, and da Silva Soares, PP. Correlation between cardiac autonomic modulation in response to orthostatic stress and indicators of quality of life, ...physical capacity, and physical activity in healthy individuals. J Strength Cond Res 29(5)1415–1421, 2015—Increased heart rate variability (HRV) at rest is frequently associated to maximal oxygen uptake ((Equation is included in full-text article.)), physical activity, and markers of quality of life (QoL). However, the HRV has not been observed during physical exercise or orthostatic (ORT) challenge. This study investigated the associations of HRV changes (ΔHRV) from rest at supine (SUP) to ORT positions with (Equation is included in full-text article.), physical activity level, and QoL in young adults. Cardiac autonomic modulation was assessed by spectral analysis of R-R time series measured from SUP to ORT positions in 15 healthy volunteers (26 ± 7 years). Questionnaires were applied for evaluation of QoL (SF-36 score), to estimate (Equation is included in full-text article.), and to quantify physical activity (Baecke Sport Score). All HRV indices at SUP, but not ORT, strongly correlated to QoL, estimated (Equation is included in full-text article.), and physical activity. The ΔHRV from SUP to ORT showed significant correlations with all questionnaire scores (r = 0.52–0.61 for low frequency and r = −0.61 to −0.65 for high frequency, p ≤ 0.05). Higher vagal activity at rest and greater changes in adrenergic and parasympathetic modulation from SUP to ORT were detected in the volunteers exhibiting higher scores of QoL, estimated (Equation is included in full-text article.), and physical activity. Taken together, the level of neural adaptations from resting SUP position to active standing, and physical activity and QoL questionnaires seem to be a simple approach to understand the physiological and lifestyle adaptations to exercise that may be applied to a large sample of subjects in almost any sports facilities at a low cost.
Purpose: This study aimed to compare blood pressure (BP) after isolated and combined sessions of aerobic and resistance exercises in hypertensive older women. Heart rate (HR) and heart rate ...variability (HRV) were included as additional variables. Methods: Twenty-one older women (63±1.9 years; 69.9±2.7 kg; 158.8±2.1 cm) with controlled hypertension (resting BP = 132.2 ± 3.1/74.1 ± 4.0 mmHg) performed four random sessions on different days: 1) aerobic exercise (AE: treadmill walking/running; 40 min; 50-60% HR
reserve
); 2) resistance exercise (RE: 8 exercises; 3 sets; 15 reps; 40% 1RM)); 3) aerobic exercise followed by resistance exercise (A+R); 4); control (CON). BP, HR and HRV were measured at rest and during 180 min after the sessions. Results: The AE and A+R sessions demonstrated significant decreases in SBP and DBP (30, 60, 120, and 180 min; P < 0.05) and increases in HR (30 and 60 min; P < 0.05) compared to the CON. The RE session demonstrated significant reductions compared to the CON only for DBP (120 and 180 min; P < 0.05). No significant differences were observed in HRV between resting and all sessions. Conclusion: All sessions that involved aerobic exercise (AE and A+R) caused postexercise hypotension in comparison to the CON, with no differences in HRV.
Post-stroke patients usually exhibit reduced peak muscular torque (PT) and/or force steadiness during submaximal exercise. Brain stimulation techniques have been proposed to improve neural plasticity ...and help to restore motor performance in post-stroke patients. The present study compared the effects of bihemispheric motor cortex transcranial direct current stimulation (tDCS) on PT and force steadiness during maximal and submaximal resistance exercise performed by post-stroke patients vs. healthy controls. A double-blind randomized crossover controlled trial (identification number: TCTR20151112001; URL: http://www.clinicaltrials.in.th/) was conducted involving nine healthy and 10 post-stroke hemiparetic individuals who received either tDCS (2 mA) or sham stimulus upon the motor cortex for 20 min. PT and force steadiness (reflected by the coefficient of variation (CV) of muscular torque) were assessed during unilateral knee extension and flexion at maximal and submaximal workloads (1 set of 3 repetitions at 100% PT and 2 sets of 10 repetitions at 50% PT, respectively). No significant change in PT was observed in post-stroke and healthy subjects. Force steadiness during knee extension (~25-35%, P < 0.001) and flexion (~22-33%, P < 0.001) improved after tDCS compared to the sham condition in post-stroke patients, but improved only during knee extension (~13-27%, P < 0.001) in healthy controls. These results suggest that tDCS may improve force steadiness, but not PT in post-stroke hemiparetic patients, which might be relevant in the context of motor rehabilitation programs.
The purpose of this study was to investigate the influence of different resistance exercise orders on the number of repetitions performed to failure and on the ratings of perceived exertion (RPE) in ...trained women. Twenty-three women with a minimum of 2 years of resistance training experience volunteered to participate in the study (age, 24.2 ± 4.5 years; weight, 56.9 ± 4.7 kg; height, 162.3 ± 5.9 cm; percent body fat, 18.2 ± 2.9%; body mass index, 22.2 ± 2 kg·m). Data were collected in 2 phases(a) determination of a 1 repetition maximum (1RM) for the leg-press (LP), bench press (BP), leg extension (LE), seated machine shoulder press (SP), leg curl (LC), and seated machine triceps extension (TE); and (b) execution of 3 sets, with 2-minute rest intervals between sets and exercises, until fatigue using 80% of 1RM in 2 exercise sequences of the exact opposite order—Sequence ABP, SP, TE, LP, LE, and LC, and Sequence BLC, LE, LP, TE, SP, and BP. The RPE (Borg CR-10) was accessed immediately after each sequence and analyzed using a Wilcoxon test. A 2-way analysis of variance with repeated measurements, followed by a post hoc Fisher least significant difference test where indicated was used to analyze the number of repetitions per set of each exercise during the 2 sequences. The RPE was not significantly different between the sequences. The mean number of repetitions per set was always less when an exercise was performed later in the exercise sequence. The data indicate that in trained women, performance of both large- and small-muscle group exercises is affected by exercise sequence.
People living with HIV (PLHIV) present impaired muscle metaboreflex, which may lead to exercise intolerance and increased cardiovascular risk. The muscle metaboreflex adaptations to exercise training ...in these patients are unknown. The present study aims to investigate the effects of a supervised multimodal exercise training on hemodynamic and autonomic responses to muscle metaboreflex activation in PLHIV.
In this randomized clinical trial protocol, 42 PLHIV aged 30-50 years will be randomly assigned at a ratio of 1:1 into an intervention or a control group. The intervention group will perform exercise training (3x/week during 12 weeks) and the control group will remain physically inactive. A reference group composed of 21 HIV-uninfected individuals will be included. Primary outcomes will be blood pressure and heart rate variability indices assessed during resting, mental stress, and activation of muscle metaboreflex by a digital sphygmomanometer and a heart rate monitor; respectively. Mental stress will be induced by the Stroop Color-Word test and muscle metaboreflex will be activated through a post-exercise circulatory arrest (PECA) protocol, being the latter performed without and with the application of a capsaicin-based analgesic balm in the exercised limb. Secondary outcomes will be heart rate, peripheral vascular resistance, stroke volume, cardiac output, blood lactate, anthropometric markers and handgrip maximal voluntary contraction. The intervention and control groups of PLHIV will be evaluated at baseline and after the intervention, while the HIV-uninfected reference group only at baseline.
The findings of the present study may help to elucidate the muscle metaboreflex adaptations to exercise training in PLHIV.
This study will be performed at University of Rio de Janeiro State following registration at ClinicalTrials.gov as NCT04512456 on August 13, 2020.
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