Felipe A. Cunha

Prefrontal cortex transcranial direct current stimulation associated with aerobic exercise change aspects of appetite sensation in overweight adults

This study investigated whether transcranial direct current stimulation (tDCS) on dorsolateral prefrontal cortex (DLPFC) isolated or combined with aerobic exercise influenced the desire to eat, hunger, and satiety in overweight subjects. Nine volunteers underwent anodal or sham tDCS (2 mA; 20 min) over DLPFC and isocaloric exercise bouts (70%VO(2)R; ~200 kcal). The appetite sensations were evaluated by visual analogue scales at four moments: I - Baseline; II - After tDCS; III - Post-Exercise and IV - 30-min Post-Exercise. The tDCS on left DLPFC decreased the desire to eat at baseline (tDCS -26% vs. -14% Sham). The tDCS associated with exercise had greater suppressing effect in desire to eat compared to either tDCS or exercise alone (tDCS -39% vs. -27% Sham). Moreover, the tDCS associated with exercise decreased hunger (tDCS -48% vs. 36% Sham) and increased satiety (tDCS 28% vs. 7% Sham) immediately after exercise. The post-exercise 30-min recovery elicited an overall increase in appetite. However the increase in desire to eat and hunger after recovery was lower after tDCS (29% and 13%, respectively) compared to sham stimulation (77% and 113%, respectively). These findings in overweight subjects indicate that the combination of tDCS over DLPFC and aerobic exercise induced greater decrease in appetite sensations compared to anodal tDCS or exercise alone.

Transcranial direct current stimulation influences the cardiac autonomic nervous control

To investigate whether the manipulation of brain excitability by transcranial direct current stimulation (tDCS) modulates the heart rate variability (HRV), the effect of tDCS applied at rest on the left temporal lobe in athletes (AG) and non-athletes (NAG) was evaluated. The HRV parameters (natural logarithms of LF, HF, and LF/HF) was assessed in 20 healthy men before, and immediately after tDCS and sham stimulation. After anodal tDCS in AG the parasympathetic activity (HF(log)) increased (P<0.01) and the sympathetic activity (LF(log)) and sympatho-vagal balance (LF/HF(log)) decreased (P<0.01), whereas no significant effects were detected in NAG (P>0.05). No significant changes in HRV indexes were provoked by sham stimulation in both AG and NAG (P>0.05). In conclusion, tDCS applied on the left temporal lobe significantly increased the overall HRV in AG, enhancing the parasympathetic and decreasing the sympathetic modulation of heart rate. Consequently the sympatho-vagal balance decreased at rest in AG but not in NAG. Releasing a weak electric current to stimulate selected brain areas may induce favorable effects on the autonomic control to the heart in highly fit subjects.

Methodological and practical application issues in exercise prescription using the heart rate reserve and oxygen uptake reserve methods

Exercise intensity is an important aspect of enhancing health-related fitness. Relationships between the percentages of heart rate reserve (%HRR), maximal oxygen uptake (%VO(2max)) and oxygen uptake reserve (%VO₂R) have been proposed as being effective for exercise intensity prescription. The present paper reviewed experimental studies published between 1966 and 2010, which investigated the relationships between the %HRR, %VO(2max) and %VO₂R. The following aspects were focused upon: (a) comparisons of the relationships between %HRR, %VO(2max) and %VO₂R at different exercise intensities; (b) methodological differences in determining resting VO₂ and VO(2max) and associated effects on the above relationships; (c) applicability of the %HRR-%VO(2max) and %HRR-%VO₂R relationships for exercise prescription. Fifteen studies published between 1997 and 2010 met inclusion criteria. Five studies observed the %HRR-%VO₂R relationship, while the others also investigated the %HRR-%VO(2max) relationship. Six studies found that the %HRR was closer to the %VO₂R than the %VO(2max). Most studies did not satisfy the recommended methodological criteria for assessing the resting VO₂, or used incremental test protocols which may have underestimated VO(2max). None investigated the stability of the %HRR-%VO₂R relationship in training conditions, such as during prolonged submaximal exercise. In conclusion, many of the reviewed studies presented methodological limitations that compromised their results in relation to the application of the %HRR-%VO₂R relationship for prescribing aerobic training.

Influence of Cardiopulmonary Exercise Testing Protocol and Resting VO2 Assessment on %HRmax, %HRR, %VO2max and %VO2R Relationships

The findings of previous studies investigating the strength of the relationships between the percentages of maximal heart rate (%HR(max)), heart rate reserve (%HRR), maximal oxygen uptake (%VO(2max)), and oxygen uptake reserve (%VO(2)R) have been equivocal. This inconsistency between studies could largely be due to differences in methodology. The purpose of this study was therefore to determine whether different VO(2max) test protocols and resting VO(2) assessment influence the relationships between the %HR(max), %HRR, %VO(2max), and %VO(2)R. Thirty-three young men performed maximal treadmill protocols (ramp, Bruce) to assess HR(max) and VO(2max). Resting VO(2) was assessed as follows: a) resting VO(2standard), using strict criteria (24 h exercise abstention, alcohol, soft drinks, or caffeine; 8 h fasting; 30 min assessment); b) resting VO(2sitting) and; c) resting VO(2standing) (both 5 min before exercise testing). The %HRR was closer to %VO(2max) than to %VO(2)R, especially in the ramp protocol (p<0.001). In the Bruce protocol, relationships were closer to the identity line, and there was no significant difference between %HRR and %VO(2max), or %VO(2)R. The VO(2max) was significantly higher in the ramp protocol compared to the Bruce protocol (p<0.001). In both protocols resting VO(2) assessment produced no significant difference in the intercepts and slopes of the %HRR-%VO(2)R relationships obtained from individual regression models. The %VO(2)R calculated using resting VO(2standard) was closer to %HRR compared to VO(2sitting) and VO(2standing). The premise that %HRR is more strongly related to %VO(2)R than to %VO(2max) was not confirmed. Methodological differences should be considered when interpreting previous studies investigating %HR(max), %HRR, %VO(2max), and %VO(2)R relationships.

Aerobic Exercise Intensity Influences Hypotension Following Concurrent Exercise Sessions

The study investigated whether resistance and aerobic concurrent exercise (CE) with different intensities influenced postexercise hypotension (PEH). 21 healthy men (20.7±0.7 yr) performed 4 sessions: control [CTL 60 min of rest], and CE1, CE2, and CE3 consisting respectively of 2 sets of 6 exercises at 80% 1RM followed by 30 min of cycle ergometer exercise at 50%, 65%, and 80% of peak oxygen consumption (VO2peak). All sessions lasted approximately 60 min and began with resistance prior to aerobic sessions. Systolic (SBP) and diastolic (DBP) blood pressure (BP) were assessed at baseline and every 10 min during 120-min recovery. The magnitude of SBP decrease was similar after all CE sessions [CE1: 4.2±2.5 mmHg; CE2: 4.8±2.7 mmHg; CE3: 6.0±2.0 mmHg; p=0.06], but the PEH lasted approximately 1 h longer following CE2 and CE3 [120 min] compared to CE1 [60-70 min] (P<0.05). The magnitude of DBP decrease was slightly greater after CE3 and CE2 [2 mmHg] than after CE1 [1 mmHg] (P<0.05), being longer following CE3 [60 min] compared to CE2 and CE1 [40 min] (P<0.05). In conclusion, CE sessions combining resistance and aerobic sessions elicited PEH, especially when the intensity of the aerobic exercise was higher than 65% VO2peak.

Determination of Best Criteria to Determine Final and Initial Speeds within Ramp Exercise Testing Protocols

This study compared strategies to define final and initial speeds for designing ramp protocols. V O2max  was directly assessed in 117 subjects (29 ± 8 yrs) and estimated by three nonexercise models: (1) Veterans Specific Activity Questionnaire (VSAQ); (2) Rating of Perceived Capacity (RPC); (3) Questionnaire of Cardiorespiratory Fitness (CRF). Thirty seven subjects (30 ± 9 yrs) performed three additional tests with initial speeds corresponding to 50% of estimated V O2max  and 50% and 60% of measured V O2max . Significant differences (P < 0.001) were found between V O2max  measured (41.5 ± 6.6 mL·kg−1 ·min−1) and estimated by VSAQ (36.6 ± 6.6 mL·kg−1 ·min−1) and CRF (45.0 ± 5.3 mL·kg−1 ·min−1), but not RPC (41.3 ± 6.2 mL·kg−1 ·min−1). The CRF had the highest ICC, the lowest SEE, and better limits of agreement with V O2max  compared to the other instruments. Initial speeds from 50%–60% V O2max  estimated by CRF or measured produced similar V O2max  (40.7 ± 5.9; 40.0 ± 5.6; 40.3 ± 5.5 mL·kg−1 ·min−1 resp., P = 0.14). The closest relationship to identity line was found in tests beginning at 50% V O2max  estimated by CRF. In conclusion, CRF was the best option to estimate V O2max  and therefore to define the final speed for ramp protocols. The measured V O2max  was independent of initial speeds, but speeds higher than 50% V O2max  produced poorer submaximal relationships between workload and V O2.

The relationship between oxygen uptake reserve and heart rate reserve is affected by intensity and duration during aerobic exercise at constant work rate

The relationship between the percentage of heart rate reserve (%HRR) and percentage of oxygen uptake reserve (%VO₂R) 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 %VO₂R-%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 (VO₂(max)) and (ii) three 40-min exercise bouts at 60%, 70%, and 80% VO₂R. HR and VO₂ 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 %VO₂R, and between %HRR and %VO₂(max), was not observed, with mean differences of 8% (t = 5.2, p < 0.001) and 6% (t = 4.8, p < 0.001), respectively. The VO₂ values predicted from the ACSM running equation were all significantly higher than the observed VO₂ values (p < 0.001 for all comparisons), whereas a difference for HR was observed only for the tenth min of exercise at 80% VO₂R (p = 0.041). In conclusion, the main finding of this study was that the %HRR-%VO₂R relationship determined by linear regression, obtained from progressive maximal exercise testing, did not apply to prolonged treadmill running performed at 3 work rates.

Effect of continuous and intermittent bouts of isocaloric cycling and running exercise on excess postexercise oxygen consumption

OBJECTIVES The purpose of this study was to investigate excess postexercise oxygen consumption (EPOC) induced by isocaloric bouts of continuous and intermittent running and cycling exercise. DESIGN This was a counterbalanced randomized cross-over study. METHODS Ten healthy men, aged 23-34yr, performed six bouts of exercise: (a) two maximal cardiopulmonary exercise tests for running and cycling to determine exercise modality-specific peak oxygen uptake (VO2peak); and (b) four isocaloric exercise bouts (two continuous bouts expending 400kcal and two intermittent bouts split into 2×200kcal) performed at 75% of the running and cycling oxygen uptake reserve. Exercise bouts were separated by 72h and performed in a randomized, counter-balanced order. The VO2 was monitored for 60-min postexercise and for 60-min during a control non-exercise day. RESULTS The VO2 was significantly greater in all exercise conditions compared to the control session (P<0.001). The combined magnitude of the EPOC from the two intermittent bouts was significantly greater than that of the continuous cycling (mean difference=3.5L, P=0.001) and running (mean difference=6.4L, P<0.001). The exercise modality had a significant effect on net EPOC, where running elicited a higher net EPOC than cycling (mean difference=2.2L, P<0.001). CONCLUSIONS Intermittent exercise increased the EPOC compared to a continuous exercise bout of equivalent energy expenditure. Furthermore, the magnitude of EPOC was influenced by exercise modality, with the greatest EPOC occurring with isocaloric exercise involving larger muscle mass (i.e., treadmill running vs. cycling).

Influence of exercise modality on agreement between gas exchange and heart rate variability thresholds

The main purpose of this study was to investigate the level of agreement between the gas exchange threshold (GET) and heart rate variability threshold (HRVT) during maximal cardiopulmonary exercise testing (CPET) using three different exercise modalities. A further aim was to establish whether there was a 1:1 relationship between the percentage heart rate reserve (%HRR) and percentage oxygen uptake reserve (%V˙O2 R) at intensities corresponding to GET and HRVT. Sixteen apparently healthy men 17 to 28 years of age performed three maximal CPETs (cycling, walking, and running). Mean heart rate and V˙O2 at GET and HRVT were 16 bpm (P<0.001) and 5.2 mL·kg-1·min-1 (P=0.001) higher in running than cycling, but no significant differences were observed between running and walking, or cycling and walking (P>0.05). There was a strong relationship between GET and HRVT, with R2 ranging from 0.69 to 0.90. A 1:1 relationship between %HRR and %V˙O2 R was not observed at GET and HRVT. The %HRR was higher during cycling (GET mean difference=7%; HRVT mean difference=11%; both P<0.001), walking (GET mean difference=13%; HRVT mean difference=13%; both P<0.001), or running (GET mean difference=11%; HRVT mean difference=10%; both P<0.001). Therefore, using HRVT to prescribe aerobic exercise intensity appears to be valid. However, to assume a 1:1 relationship between %HRR and %V˙O2 R at HRVT would probably result in overestimation of the energy expenditure during the bout of exercise.

Does Prefrontal Cortex Transcranial Direct Current Stimulation Influence the Oxygen Uptake at Rest and Post-exercise?

The study evaluated the effect of transcranial direct current stimulation (tDCS) applied over prefrontal cortex on the oxygen uptake (V˙ O2) at rest and during post-exercise recovery. The V˙ O2 was assessed in eleven healthy subjects before, during tDCS (sham or anodal tDCS, 2 mA, 20 min), and 30-min following isocaloric aerobic exercise (~200 kcal). During tDCS, no changes were observed on V˙ O2 compared to baseline (P=0.95) and sham condition (P=0.85). The association between isocaloric exercise and anodal tDCS increased the V˙ O2 throughout 30-min recovery compared to sham condition (P