How long does it take to achieve steady state for an accurate assessment of resting VO₂ in healthy men?

Excess Postexercise Oxygen Consumption Following Isocaloric Bouts of Resistance and Aerobic Exercise in Older Adults

Purpose: Albeit being a major determinant of exercise-related energy expenditure (EE), there is a lack of research on the excess post-exercise oxygen consumption (EPOC) after different exercise modalities in older adults. This study compared the EPOC after isocaloric bouts of resistance (RE) and aerobic (AE) exercise. Methods: The EE during exercise was determined through telemetric indirect calorimetry in ten physically active participants aged 63 to 82 years (5 women, 73 ± 6 years, 70.5 ± 9.9 kg, 161 ± 8 cm). The target EE in AE corresponded to values achieved during RE, and the EPOC was assessed for 30 min in the supine position. Results: The EE during AE and RE were 126.0 ± 30.7 kcal and 123.9 ± 30.6 kcal, respectively. The time to achieve the target EE was 2.3 times shorter in AE vs. RE. The EPOC magnitude was greater after AE (7.9 ± 2.4 L, 40.1 ± 11.1 kcal) than RE (5.9 ± 1.8 L, 26.9 ± 11.5 kcal). Conclusion: Older adults showed greater EPOC after isocaloric sessions of AE vs. RE. Additionally, AE had better temporal efficiency than RE to elicit a given EE.

Can mixed circuit training elicit the recommended exercise intensity and energy expenditure in people after stroke?

PURPOSE

To investigate whether mixed circuit training (MCT) elicits the recommended exercise intensity and energy expenditure in people after stroke, and to establish the between-day reproducibility for the percentages of heart rate reserve (%HRR), oxygen uptake reserve (%VO2R), and energy expenditure elicited during two bouts of MCT.

METHODS

Seven people aged 58 (12) yr, who previously had a stroke, performed a cardiopulmonary exercise test, a non-exercise control session, and two bouts of MCT. The MCT included 3 circuits of 10 resistance exercises at 15-repetition maximum intensity, with each set of resistance exercise interspersed with 45-s of walking. Expired gases were collected during the MCT and control session and for 40 min afterward. Control session was necessary to calculate the net energy expenditure associated with each bout of MCT.

RESULTS

Mean %VO2R (1st MCT: 51.1%, P = .037; 2nd MCT: 54.0%, P = .009) and %HRR (1st MCT: 66.4%, P = .007; 2nd MCT: 67.9%, P = .010) exceeded the recommended minimum intensity of 40%. Both %VO2R (P = .586 and 0.987, respectively) and %HRR (P = .681 and 0.237, respectively) during the 1st and 2nd bouts of MCT were not significantly different to their corresponding gas exchange threshold values derived from cardiopulmonary exercise testing. Mean net total energy expenditure significantly exceeded the minimum recommend energy expenditure in the 1st (P = .048) and 2nd (P = .023) bouts of MCT. Between-day reproducibility for %HRR, %VO2R, and energy expenditure was excellent (ICC: 0.92-0.97).

CONCLUSIONS

MCT elicited physiological strain recommended for improving health-related fitness in people after stroke and these responses demonstrated excellent between-day reproducibility.

Self-selected or fixed: is there an optimal rest interval for controlling intensity in high-intensity interval resistance training?

PURPOSE

This study investigated the effects of different rest interval strategies during high-intensity interval resistance training (HIRT) on cardiorespiratory, perceptual, and enjoyment responses among trained young men.

METHODS

Sixteen men experienced with HIRT underwent cardiopulmonary exercise testing and were familiarized with the exercises and HIRT protocol. On the subsequent three visits, interspaced 48-72 h, participants performed HIRT sessions with different rest intervals in a randomized order: 10 s and 30 s fixed rest intervals (FRI-10 and FRI-30), and self-selected rest interval (SSRI). Oxygen uptake (VO2), heart rate (HR), and recovery perception (Total Quality Recovery Scale) were measured during HIRT, while enjoyment responses (Physical Activity Enjoyment Scale) were assessed immediately after the sessions.

RESULTS

The VO2 during exercise was greater in FRI-10 than FRI-30 (55% VO2max and 47% VO2max, respectively, p = 0.01), while no difference occurred between SSRI and bouts performed with fixed intervals (52% VO2max vs. FRI, p > 0.05). HR, excess post-exercise oxygen consumption (EPOC), recovery perception, and enjoyment responses were similar across conditions (p > 0.05).

CONCLUSION

Exercise intensity was not affected by the rest interval strategy. High exercise intensity was maintained in sessions performed with FRI or SSRI, without negative repercussions on the duration of training sessions and enjoyment responses after exercise sessions.

Is postexercise hypotension a method-dependent phenomenon in chronic stroke? A crossover randomized controlled trial

BACKGROUND

This study assessed the reproducibility of postexercise hypotension (PEH) detection after two bouts of mixed circuit training (MCT) using three approaches that accounts the pre-exercise values and/or a control session (CTL) to calculate PEH [i.e., ( A 1 = post - exercise - pre - exercise ${A}_{1}=\text{post}{\rm{ \mbox{-} }}\text{exercise}-\text{pre}{\rm{ \mbox{-} }}\text{exercise}$ ); ( A 2 = post - exercise - post - CTL ) $({A}_{2}=\text{post}{\rm{ \mbox{-} }}\text{exercise}-\text{post}{\rm{ \mbox{-} }}\text{CTL})$ ; A 3 = ( post - exercise - pre - exercise ) - ( post - CTL - pre - CTL ) ] ${A}_{3}=(\text{post}{\rm{ \mbox{-} }}\text{exercise}-\text{pre}{\rm{ \mbox{-} }}\text{exercise})-(\text{post}{\rm{ \mbox{-} }}\text{CTL}-\text{pre}{\rm{ \mbox{-} }}\text{CTL})]$ in chronic stroke (i.e., ≥6 months poststroke). The proportion of PEH responders determined using different cut-off values for PEH was also compared (4 mmHg vs. minimal detectable difference).

METHODS

Seven participants (age: 56 ± 12 years; time post-stroke: 91 ± 55 months) performed two bouts of MCT and a CTL. The MCT involved 10 exercises with 3 sets of 15-repetition maximum, with each set interspersed with 45 s of walking. The systolic (SBP) and diastolic (DBP) blood pressures were assessed 10-min before and every 10-min along 40-min after CTL and MCT.

RESULTS

The two-way random intraclass correlation coefficient for single measurements (ICC_2,1 ) ranges for SBP were: A₁ : 0.580-0.829, A₂ : 0.937-0.994, A₃ : 0.278-0.774; for DBP: A₁ : 0.497-0.916, A₂ : 0.133-0.969, A₃ : 0.175-0.930. The proportion of PEH responders detected using 4 mmHg or the minimal detectable difference as cut-off values was not different in 97% of analyses (p > 0.05), and higher when using 4 mmHg in 3% of analyses (p = 0.031). The standard error of measurement was ≥4 mmHg in 47% of analyses for SBP, and 40% for DBP.

CONCLUSIONS

The most reliable approach for determining PEH in chronic stroke was to subtract the postexercise from the post-CTL values. The proportion of PEH responders was not affected by the cut-off values applied.

Mixed circuit training acutely reduces arterial stiffness in patients with chronic stroke: a crossover randomized controlled trial

PURPOSE

Investigate whether a single bout of mixed circuit training (MCT) can elicit changes in arterial stiffness in patients with chronic stroke. Second, to assess the between-day reproducibility of post-MCT arterial stiffness measurements.

METHODS

Seven participants (58 ± 12 years) performed a non-exercise control session (CTL) and two bouts of MCT on separate days in a randomized counterbalanced order. The MCT involved 3 sets of 15 repetition maximum for 10 exercises, with each set separated by 45-s of walking. Brachial-radial pulse wave velocity (br-PWV), radial artery compliance (AC) and reflection index (RI_1,2) were assessed 10 min before and 60 min after CTL and MCT. Ambulatory arterial stiffness index (AASI) was calculated from 24-h recovery ambulatory blood pressure monitoring.

RESULTS

Compared to CTL, after 60 min of recovery from the 1st and 2nd bouts of MCT, lower values were observed for br-PWV (mean diff = - 3.9 and - 3.7 m/s, respectively, P < 0.01; ICC_2,1 = 0.75) and RI_1,2 (mean diff = - 16.1 and - 16.0%, respectively, P < 0.05; ICC_2,1 = 0.83) concomitant with higher AC (mean diff = 1.2 and 1.0 × 10^-6 cm⁵/dyna, respectively, P < 0.01; ICC_2,1 = 0.40). The 24-h AASI was reduced after bouts of MCT vs. CTL (1st and 2nd bouts of MCT vs. CTL: mean diff = - 0.32 and - 0.29 units, respectively, P < 0.001; ICC_2,1 = 0.64).

CONCLUSION

A single bout of MCT reduces arterial stiffness during laboratory (60 min) and ambulatory (24 h) recovery phases in patients with chronic stroke with moderate-to-high reproducibility.

TRIAL REGISTRATION

Ensaiosclinicos.gov.br identifier RBR-5dn5zd.

Time to achieve steady state for an accurate assessment of resting energy expenditure in adolescents with healthy weight and obesity: A cross-sectional study

Objective

The present study investigated the time needed to achieve a steady state for an accurate assessment of resting energy expenditure (REE) in adolescents with healthy weight and obesity.

Methods

Thirty adolescents aged 12-17 years were assigned to a group with healthy weight (GHW; n = 12, body mass index [BMI] 22.5 ± 3.6 kg/m²) and another group with obesity (GO; n = 18, BMI 34.1 ± 5.2 kg/m²). Participants underwent test-retest reliability of REE assessment as follows: a) 24 h of abstention from physical exercise, soft drinks, or caffeine; b) fasting for ~12 h; c) acclimation period of 10 min; d) 30-min assessment in a supine position.

Results

A significant change occurred during the 30 min in REE. Significant differences existed between consecutive means until the 20^th and 25^th min for the GHW and GO, respectively. Although significant differences between trials 1 and 2 were detected during the first 5-10 min of assessment, the REE for each 5-min time point exhibited high test-retest reliability across trials in both groups (intraclass correlation coefficients range 0.79-0.99).

Conclusion

The following recommendations are provided to promote accurate assessment of REE among adolescents: a) initiate the REE assessment with 10 min of acclimation to decrease restlessness; b) determine REE for a minimum of 20 min if healthy weight and 25 min if obesity; c) determine REE for a further 5 min, with the average of this last 5 min of REE data being regarded as the REE.

Appetite and energy intake following a bout of circuit resistance training in chronic hemiparetic stroke patients: a preliminary randomized controlled trial

PURPOSE

The main aim of this study was to investigate the effects of circuit resistance training (CRT) on post-exercise appetite and energy intake in chronic hemiparetic stroke patients. A secondary aim was to evaluate the reproducibility of these effects.

METHODS

Seven participants met the eligibility criteria and, in a randomized order, participated in a non-exercise control session (CTL) and two bouts of CRT. The CRT involved 10 exercises with 3 sets of 15-repetition maximum per exercise, performed using a vertical loading approach, with each set interspersed with 45s of walking. Expired gases were carried out   to calculate the net energy cost of the exercise and the relative energy intake post-CTL/CRT. Hunger, fullness, desire to eat, and energy intake were assessed at baseline and for 12 h after CTL and CRT.

RESULTS

Compared to CTL, hunger, desire to eat (P < .001), and relative energy intake (P < .05) were significantly lower after CRT, whereas the perception of fullness was significantly higher (P < .001). Significant differences between CTL and CRT were observed only for the first 9 h of the post-exercise period for hunger, fullness, and desire to eat (P < .05). No significant differences in appetite or relative energy intake were observed between the two bouts of CRT.

CONCLUSIONS

A bout of CRT elicited decreased post-exercise appetite and relative energy intake in chronic hemiparetic stroke patients. Decreased appetite perceptions lasted for around 9 h and were reproducible.

The estimation of the resting metabolic rate is affected by the method of gas exchange data selection in high-level athletes

BACKGROUND & AIMS

there is no consensus in the literature about the best method to estimate the RMR in a high-level athlete's cohort. Additionally, a shortening protocol may allow researchers, nutritionists, and clinicians to follow the RMR across the season and to propose better nutritional interventions, but this kind of protocol was not proposed in this cohort yet. Thus, this study aims to analyze the effect of the method of gas exchange data selection upon the RMR estimate and, possibly propose a shortening protocol with a valid and accurate RMR value.

METHODS

Eighty-three healthy high-level athletes underwent a 30-minute RMR measurement with no rest period before the test. Different methods of gas exchange data selection were used: short and long time intervals (TI) [6-10, 11-15, 16-20, 21-25, 26-30, 6-25, or 6-30], Steady State (SS) with 3, 4, 5, or 10 min period length, and Filtering (low, medium, and high). Single and multiple linear regressions were used to examine the variance in the RMR provided by each method of gas exchange data selection.

RESULTS

The High Filter method provided the lowest RMR estimate (1854 kcal.day^-1), and most methods presented a mean absolute difference of ~43 kcal.day^-1 from the High Filter method. There were no differences in RER among methods (F = 2.01, p = 0.10). Besides, twenty minutes of gas exchange measurement was necessary to obtain a valid and accurate RMR with no rest period before the test. The linear regression model that included sex, lean body mass, and fat mass better explained the variance in the RMR using the high filter method (~88%).

CONCLUSIONS

The High Filter provided the lowest RMR value. Furthermore, a 20-minute protocol estimated a valid and accurate RMR value with no acclimation period before the measurement in high-level athletes.

Postexercise hypotension and related hemodynamic responses to cycling under heat stress in untrained men with elevated blood pressure

PURPOSE

To investigate the effect of heat stress on postexercise hypotension.

METHODS

Seven untrained men, aged 21-33 years, performed two cycling bouts at 60% of oxygen uptake reserve expending 300 kcal in environmental temperatures of 21 °C (TEMP) and 35 °C (HOT) in a randomized, counter-balanced order. Physiological responses were monitored for 10-min before and 60-min after each exercise bout, and after a non-exercise control session (CON). Blood pressure (BP) also was measured during the subsequent 21-h recovery period.

RESULTS

Compared to CON, systolic, and diastolic BPs were significantly reduced in HOT (Δ = - 8.3 ± 1.6 and - 9.7 ± 1.4 mmHg, P < 0.01) and TEMP (Δ = - 4.9 ± 2.1 and - 4.5 ± 0.9 mmHg, P < 0.05) during the first 60 min of postexercise recovery. Compared to TEMP, rectal temperature was 0.6 °C higher (P = 0.001), mean skin temperature was 1.8 °C higher (P = 0.013), and plasma volume (PV) was 2.6 percentage points lower (P = 0.005) in HOT. During the subsequent 21-h recovery period systolic BP was 4.2 mmHg lower in HOT compared to CON (P = 0.016) and 2.5 mmHg lower in HOT compared to TEMP (P = 0.039).

CONCLUSION

Exercise in the heat increases the hypotensive effects of exercise for at least 22 h in untrained men with elevated blood pressure. Our findings indicate that augmented core and skin temperatures and decreased PV are the main hemodynamic mechanisms underlying a reduction in BP after exercise performed under heat stress.

Concurrent exercise circuit protocol performed in public fitness facilities meets the American College of Sports Medicine guidelines for energy cost and metabolic intensity among older adults in Rio de Janeiro City

The current study investigated whether a single bout of concurrent exercise (Ex Rx) at Third Age Academies (TAAs) in Rio de Janeiro City meets the American College of Sports Medicine (ACSM) guidelines for energy cost and metabolic intensity in older adults. Nine subjects (5 males and 4 females, 63-80 years of age) visited the laboratory for clinical screening and for anthropometrical, resting, and maximal oxygen uptake assessments. Thereafter, subjects performed an Ex Rx circuit consisting of a single circuit alternating aerobic and resistance exercises with outdoor exercise equipment using body mass as the load (total of 9 exercises, 1-2 sets of 15 repetitions). Expired gases were collected via a metabolic cart during exercise bouts. The mean observed energy cost value of 169.1 kcal was slightly greater than the minimum value of 150 kcal reported in the ACSM guidelines (p = 0.018). Like energy cost, all the intensity markers adopted to analyze the physiological strain induced by the Ex Rx circuit significantly exceeded their reference values for moderate intensity (reference values: 3.2 METs (mean observed value = 4.6 METs, p = 0.002); 40% of oxygen uptake reserve (mean observed value = 51.5%, p = 0.040); 40% of heart rate reserve (mean observed value = 64.1%, p < 0.001)), according to the ACSM guidelines. In conclusion, a single bout of Ex Rx circuit performed at TAAs in Rio de Janeiro City was able to induce a physiological strain (i.e., energy cost and intensity) compatible with ACSM recommendations for eliciting health benefits among older adults.

Continuous and Accumulated Bouts of Cycling Matched by Intensity and Energy Expenditure Elicit Similar Acute Blood Pressure Reductions in Prehypertensive Men

Fonseca, GF, Farinatti, PTV, Midgley, AW, Ferreira, A, de Paula, T, Monteiro, WD, and Cunha, FA. Continuous and accumulated bouts of cycling matched by intensity and energy expenditure elicit similar acute blood pressure reductions in prehypertensive men. J Strength Cond Res 32(3): 857-866, 2018-This study investigated differences in postexercise hypotension (PEH) after continuous vs. accumulated isocaloric bouts of cycling. Ten prehypertensive men, aged 23-34 years, performed 2 bouts of cycling at 75% oxygen uptake reserve, with total energy expenditures of 400 kcal per bout. One exercise bout was performed continuously (CONTIN) and the other as 2 smaller bouts each expending 200 kcal (INTER1 and INTER2). Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and cardiac autonomic control were monitored in a supine position for 10 minutes before and 60 minutes after each exercise bout, and during a control session. Compared with control, blood pressure was significantly reduced after CONTIN (SBP: [INCREMENT] - 3.4 mm Hg, p < 0.001; MAP: [INCREMENT] - 2.5 mm Hg, p = 0.001), INTER1 (SBP: [INCREMENT] - 2.2 mm Hg, p = 0.045), and INTER2 (SBP: [INCREMENT] - 4.4 mm Hg, p < 0.001; DBP: [INCREMENT] - 2.7 mm Hg, p = 0.045; MAP: [INCREMENT] - 3.3 mm Hg, p = 0.001). The PEH was similar in CONTIN and INTER2, whereas INTER2 elicited greater PEH than INTER1 (SBP and MAP: [INCREMENT] - 2.0 and [INCREMENT] - 1.8 mm Hg, respectively, p ≤ 0.05). Increases in sympathovagal balance from baseline were inversely related to changes in SBP and DBP after CONTIN and INTER2 (r = -0.64 to -0.71; p = 0.021-0.047). These findings indicate that similar amounts of PEH are observed when exercise is performed as a single 400-kcal exercise bout or 2 × 200-kcal bouts and that the exercise recovery pattern of cardiac autonomic activity may be important in eliciting PEH.

Relationship Between Percentages of Heart Rate Reserve and Oxygen Uptake Reserve During Cycling and Running: A Validation Study

Guimarães, GC, Farinatti, PTV, Midgley, AW, Vasconcellos, F, Vigário, P, and Cunha, FA. Relationship between percentages of heart rate reserve and oxygen uptake reserve during cycling and running: a validation study. J Strength Cond Res 33(7): 1954-1962, 2019-This study investigated the relationship between percentages of heart rate reserve (%HRR) and oxygen uptake reserve (%VO2R) during a cardiopulmonary exercise test (CPET) and discrete bouts of isocaloric cycling and treadmill running. Thirty men visited the laboratory 3 times for anthropometrical and resting VO2 assessments, and perform cycling and running CPETs. Ten men visited the laboratory twice more to investigate the validity of the %HRR-%VO2R relationships during isocaloric bouts of cycling and running at 75% VO2R with energy expenditures of 400 kcals. The %HRR was significantly higher than the %VO2R during both CPETs at all exercise intensities (p < 0.001). During isocaloric exercise bouts, mean %HRR-%VO2R differences of 6.5% and 7.0% were observed for cycling and running, respectively (p = 0.007-p < 0.001). The %HRR and %VO2R increased over time (p < 0.001), the rate of which was influenced by exercise modality (p < 0.001). On average, heart rate was 5 (p = 0.007) and 8 (p < 0.001) b·min higher than predicted from the second energy expenditure quartile for cycling and running, respectively; however, observed VO2 was lower than predicted during all quartiles for cycling, and the first quartile for running. Consequently, time to achieve the target energy expenditure was greater than predicted (p < 0.01). In conclusion, the %HRR-%VO2R relationship observed during CPET data did not accurately transpose to prolonged isocaloric bouts of cycling and running. In addition, power outputs and speeds defined by the American College of Sports Medicine equations for cycling and running, respectively, overestimated VO2 and energy expenditure.

Open-circuit respirometry: a brief historical review of the use of Douglas bags and chemical analyzers

The Douglas bag technique is reviewed as one in a series of articles looking at historical insights into measurement of whole body metabolic rate. Consideration of all articles looking at Douglas bag technique and chemical gas analysis has here focused on the growing appreciation of errors in measuring expired volumes and gas composition, and subjective reactions to airflow resistance and dead space. Multiple small sources of error have been identified and appropriate remedies proposed over a century of use of the methodology. Changes in the bag lining have limited gas diffusion, laboratories conducting gas analyses have undergone validation, and WHO guidelines on airflow resistance have minimized reactive effects. One remaining difficulty is a contamination of expirate by dead space air, minimized by keeping the dead space <70 mL. Care must also be taken to ensure a steady state, and formal validation of the Douglas bag method still needs to be carried out. We may conclude that the Douglas bag method has helped to define key concepts in exercise physiology. Although now superceded in many applications, the errors in a meticulously completed measurement are sufficiently low to warrant retention of the Douglas bag as the gold standard when evaluating newer open-circuit methodology.

Physiological responses and external validity of a new setting for taekwondo combat simulation

Combat simulations have served as an alternative framework to study the cardiorespiratory demands of the activity in combat sports, but this setting imposes rule-restrictions that may compromise the competitiveness of the bouts. The aim of this study was to assess the cardiorespiratory responses to a full-contact taekwondo combat simulation using a safe and externally valid competitive setting. Twelve male national level taekwondo athletes visited the laboratory on two separate occasions. On the first visit, anthropometric and running cardiopulmonary exercise assessments were performed. In the following two to seven days, participants performed a full-contact combat simulation, using a specifically designed gas analyser protector. Oxygen uptake (V˙O2), heart rate (HR) and capillary blood lactate measurements ([La^-]) were obtained. Time-motion analysis was performed to compare activity profile. The simulation yielded broadly comparable activity profiles to those performed in competition, a mean V˙O2 of 36.6 ± 3.9 ml.kg^-1.min^-1 (73 ± 6% V˙O2PEAK) and mean HR of 177 ± 10 beats.min^-1 (93 ± 5% HR_PEAK). A peak V˙O2 of 44.8 ± 5.0 ml.kg^-1.min^-1 (89 ± 5% V˙O2PEAK), a peak heart rate of 190 ± 13 beats.min^-1 (98 ± 3% HRmax) and peak [La^-] of 12.3 ± 2.9 mmol.L^–1 was elicited by the bouts. Regarding time-motion analysis, combat simulation presented a similar exchange time, a shorter preparation time and a longer exchange-preparation ratio. Taekwondo combats capturing the full-contact competitive elements of a bout elicit moderate to high cardiorespiratory demands on the competitors. These data are valuable to assist preparatory strategies within the sport.

Influence of central obesity in estimating maximal oxygen uptake

OBJECTIVE:

To assess the influence of central obesity on the magnitude of the error of estimate of maximal oxygen uptake in maximal cycling exercise testing.

METHOD:

A total of 1,715 adults (68% men) between 18-91 years of age underwent cardiopulmonary exercise testing using a progressive protocol to volitional fatigue. Subjects were stratified by central obesity into three quartile ranges: Q1, Q2-3 and Q4. Maximal oxygen uptake [mL.(kg.min)-1] was estimated by the attained maximal workload and body weight using gender- and population-specific equations. The error of estimate [mL.(kg.min)-1] and percent error between measured and estimated maximal oxygen uptake values were compared among obesity quartile ranges.

RESULTS:

The error of estimate and percent error differed (mean ± SD) for men (Q1=1.3±3.7 and 2.0±10.4; Q2-3=0.5±3.1 and -0.5±13.0; and Q4=-0.3±2.8 and -4.5±15.8 (p<0.05)) and for women (Q1=1.6±3.3 and 3.6±10.2; Q2-3=0.4±2.7 and -0.4±11.8; and Q4=-0.9±2.3 and -10.0±22.7 (p<0.05)).

CONCLUSION:

Central obesity directly influences the magnitude of the error of estimate of maximal oxygen uptake and should be considered when direct expired gas analysis is unavailable.

Physiological strain to prolonged exercise bouts at the walk-run transition speeds depends on locomotion mode in healthy untrained men

This study compared the physiological strain induced by prolonged walking and running performed at the walk-run transition speed (WRTS) in healthy untrained men. Twenty volunteers (age: 28 ± 5.01 years; height: 174.0 ± 0.3 cm; body mass: 74.5 ± 0.6 kg) underwent the following: (a) ramp-incremental maximal cardiopulmonary exercise test (CPET); (b) specific protocol to detect the WRTS; and (c) two 30-min walking and running bouts at WRTS (mean ± SD: 6.9 ± 0.06 km/h). Expired gases were collected during exercise bouts via the metabolic cart. A significant effect of locomotion mode (F = 4.8, P < 0.001) was observed with running resulting in higher cardiorespiratory responses than walking at the WRTS (oxygen uptake: mean difference = 0.26 L/min; pulmonary ventilation: mean difference = 5.53 L/min; carbon dioxide output: mean difference = 0.32 L/min; heart rate: mean difference = 13 beats/min; total energy expenditure: mean difference = 59 kcal). The rating of perceived exertion was similar across locomotion modes (mean difference = 0.3; P = 0.490). In conclusion, running promoted greater cardiorespiratory responses than walking at the WRTS in untrained healthy men. These data might have practical impact on aerobic training performed at intensities corresponding to WRTS.

Influence of age in estimating maximal oxygen uptake

Objective

To assess the influence of age on the error of estimate (EE) of maximal oxygen uptake (VO₂max) using sex and population specific-equations in cycle ergometer exercise testing, since estimated VO₂ max is associated with a substantial EE, often exceeding 20%, possibly due to intrinsic variability of mechanical efficiency.

Methods

1850 adults (68% men), aged 18 to 91 years, underwent maximal cycle ergometer cardiopulmonary exercise testing. Cardiorespiratory fitness (CRF) was assessed relative to sex and age [younger (18 to 35 years), middle-aged (36 to 60 years) and older (> 60 years)]. VO₂max [mL·(kg·min)⁻¹] was directly measured by assessment of gas exchange and estimated using sex and population specific-equations. Measured and estimated values of VO₂max and related EE were compared among the three age- and sex-specific groups.

Results

Directly measured VO₂max of men and women were 29.5 ± 10.5 mL·(kg·min)⁻¹ and 24.2 ± 9.0 mL·(kg·min)⁻¹ (P < 0.01). EE [mL·(kg·min)⁻¹] and percent errors (%E) for men and women had similar values, 0.5 ± 3.2 and 0.4 ± 2.9 mL·(kg·min)⁻¹, and −0.8 ± 13.1% and −1.7 ± 15.4% (P > 0.05), respectively. EE and %E for each age-group were, respectively, for men: younger = 1.9 ± 4.1 mL·(kg·min)⁻¹ and 3.8 ± 10.5%, middle-aged = 0.6 ± 3.1 mL·(kg·min)⁻¹ and 0.4 ± 10.3%, older = −0.2 ± 2.7 mL·(kg·min)⁻¹ and −4.2 ± 16.6% (P < 0.01); and for women: younger = 1.2 ± 3.1 mL·(kg·min)⁻¹ and 2.7 ± 10.0%, middle-aged = 0.7 ± 2.8 mL·(kg·min)⁻¹ and 0.5 ± 11.1%, older = -0.8 ± 2.3 mL·(kg·min)⁻¹ and −9.5 ± 22.4% (P < 0.01).

Conclusion

VO₂max were underestimated in younger age-groups and were overestimated in older age groups. Age significantly influences the magnitude of the EE of VO₂max in both men and women and should be considered when CRF is estimated using population specific equations, rather than directly measured.

Health markers in obese adolescents improved by a 12-week recreational soccer program: a randomised controlled trial

The effects of a recreational soccer program (RSP) upon body composition, heart rate variability (HRV), biochemical markers, cardio-respiratory fitness, and endothelial function in obese adolescents were investigated. A randomised controlled clinical trial was conducted with 30 adolescents aged 12-17 years and body mass index (BMI) >2 standard deviations of WHO reference values, which were assigned to RSP (n = 10, 2 girls) and obese control (n = 10, 4 girls) groups. The 12-week RSP included 60-min sessions performed 3 times/week. BMI, waist circumference, blood pressure, blood glucose, lipid profile, insulin, C-reactive protein, HRV, and maximal oxygen consumption (VO2peak) were evaluated following standardised procedures. Body composition was determined by dual-energy X-ray absorptiometry and endothelial function by venous occlusion plethysmography. After intervention, RSP exhibited significant reductions in BMI (-0.7 ± 0.2 kg · m(-2)), waist circumference (-8.2 ± 1.4 cm), %body fat (-2.2 ± 0.4%), systolic blood pressure (-5.0 ± 2.3 mmHg), total cholesterol (-16.2 ± 5.8 mg · dL(-1)), triglycerides (-20.5 ± 12.9 mg · dL(-1)), C-reactive protein (-0.06 ± 0.01 mg · dL(-1)), insulin resistance (HOMA-IR, -1.4 ± 0.6), and sympathetic activity (LF, -13.9 ± 6.6 un) vs. controls (P < 0.05). Significant increase was observed in parasympathetic activity (HF, 13.9 ± 6.6 un), VO2peak (7.9 ± 2.8 ml · kg(-1) · min(-1)), and high-density lipoprotein cholesterol (11.0 ± 6.3 mg · dL(-1)) (P < 0.05). Vascular conductance (19.5 ± 8.1 ml · min(-1) · 100 ml, P = 0.005) increased and vascular resistance (-5.9 ± 2.4 ml · min(-1) · 100 ml, P = 0.041) decreased in RSP, but not in controls. A 12-week recreational soccer intervention was effective to improve biochemical, cardiovascular, and fitness health markers in obese adolescents.

Validity and reliability of Nike + Fuelband for estimating physical activity energy expenditure

Background

The Nike + Fuelband is a commercially available, wrist-worn accelerometer used to track physical activity energy expenditure (PAEE) during exercise. However, validation studies assessing the accuracy of this device for estimating PAEE are lacking. Therefore, this study examined the validity and reliability of the Nike + Fuelband for estimating PAEE during physical activity in young adults. Secondarily, we compared PAEE estimation of the Nike + Fuelband with the previously validated SenseWear Armband (SWA).

Methods

Twenty-four participants (n = 24) completed two, 60-min semi-structured routines consisting of sedentary/light-intensity, moderate-intensity, and vigorous-intensity physical activity. Participants wore a Nike + Fuelband and SWA, while oxygen uptake was measured continuously with an Oxycon Mobile (OM) metabolic measurement system (criterion).

Results

The Nike + Fuelband (ICC = 0.77) and SWA (ICC = 0.61) both demonstrated moderate to good validity. PAEE estimates provided by the Nike + Fuelband (246 ± 67 kcal) and SWA (238 ± 57 kcal) were not statistically different than OM (243 ± 67 kcal). Both devices also displayed similar mean absolute percent errors for PAEE estimates (Nike + Fuelband = 16 ± 13 %; SWA = 18 ± 18 %). Test-retest reliability for PAEE indicated good stability for Nike + Fuelband (ICC = 0.96) and SWA (ICC = 0.90).

Conclusion

The Nike + Fuelband provided valid and reliable estimates of PAEE, that are similar to the previously validated SWA, during a routine that included approximately equal amounts of sedentary/light-, moderate- and vigorous-intensity physical activity.

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 (%VO2 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 VO2 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 % VO2 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 % VO2 R at HRVT would probably result in overestimation of the energy expenditure during the bout of exercise.