Bout Of Continuous Exercise Research Articles

Do the speeds defined by the American College of Sports Medicine metabolic equation for running produce target energy expenditures during isocaloric exercise bouts?

The accuracy of the American College of Sports Medicine (ACSM) equations for producing predicted values of heart rate reserve (HRR) and oxygen uptake reserve (VO2R) and consequently, target energy expenditure (EE) during exercise are yet to be established. This study investigated whether speeds defined by the ACSM metabolic equation for running correctly estimate the EEs during isocaloric exercise bouts. Twenty-eight men performed a ramp-incremental maximal exercise test to determine HRmax and VO2max. Two continuous exercise bouts at 60 and 80% VO2R and target EE of 400 kcal were then performed. In the 60% VO2R exercise the observed VO2R and EE were lower than predicted only during the first time quartile of the bout (t = 6.5, p < 0.001), whereas at 80% VO2R it was lower during the first (t = 15.3, p < 0.001), second (t = 5.4, p < 0.001) and third (t = 3.1, p = 0.025) quartiles. The observed HR was lower than predicted in the first time quartile of the 60% [Formula: see text] (t = 5.6, p < 0.001) and 80% VO2R bouts (t = 10.7, p < 0.001), whereas no significant differences occurred for any other time quartiles (p ≥ 0.23). In conclusion, the running speed defined by the ACSM metabolic equation overestimated VO2R and EE within exercise performed at 60 and 80% VO2R especially in higher intensities.

A single versus multiple bouts of moderate-intensity exercise for fat metabolism

This study compared the fat metabolism between 'a single bout of 30-min exercise' and 'three bouts of 10-min exercise' of the same intensity (60% maximal oxygen uptake) and total exercise duration (30 min). Nine healthy men participated in three trials: (1) a single 30-min bout of exercise (Single), (2) three 10-min bouts of exercise, separated by a 10-min rest (Repeated) and (3) rest (Rest). Each exercise was performed with a cycle ergometer at 60% of maximal oxygen uptake, followed by 180-min rest. Blood lactate concentration increased significantly after exercise in the Single and Repeated trials (P < 0.05), but the Single trial showed a significantly higher value during the recovery period (P < 0.05). No significant difference was observed in the responses of plasma glycerol concentration. The Repeated trial produced a smaller increase in the ratings of perceived exertion during the exercise (P < 0.01). During the exercise, no significant difference was observed in respiratory exchange ratio (RER) between the Single and Repeated trials. However, the RER values during the recovery period were significantly lower in the Repeated trial than in the Single and Rest trials (P < 0.05), indicating higher relative contribution of fat oxidation in the Repeated trial (P < 0.05). These results suggest that the repetition of 10-min of moderate exercise can contribute to greater exercise-induced fat oxidation compared with a single 30-min bout of continuous exercise.

Muscular Angiogenic Factors and Capillary Growth - Changes with Intense Interval vs. Moderate Continuous Training.

PURPOSE: To examine the effect of a period of interval exercise training preceded by a period of continuous exercise training on angiogenic factors and capillarization in skeletal muscle. METHODS: Nine young males (intervention group) performed 60 min of continuous cycling at 62% of VO2 max 3 times/wk for 4 wks, followed by 4 wks of interval cycling consisting of 24 repetitions of 1 min bouts at 132% of VO2 max separated by 1.5 min of rest repeated 3 times/wk. In addition, five males performed 60 min of continuous cycling at 62% of VO2 max 3 times/wk for 8 wks (control group). Muscle biopsies were obtained from m. v. lateralis before as well as after 4 and 8 wks of training. Muscle interstitial fluid was collected during acute continuous cycling at week 0 and 4, and during acute interval cycling at week 4 and 8 in the intervention group. RESULTS: Intervention group: A bout of continuous exercise induced an increase in interstitial VEGF (106 ± 33 to 563 ± 131 pg/ml). A bout of interval cycling performed at 4 wks, resulted in a lower level of interstitial VEGF protein compared to continuous cycling (372 ± 107 and 690 ± 128 pg/ml, respectively; P < 0.01). Training had no effect on the magnitude of interstitial VEGF in response to exercise. Resting levels of muscle VEGF protein were 16 ± 4% lower (P < 0.05) after 4 and 8 wks of training compared to week 0 with no difference between week 4 and 8. The first 4 wks of training increased (50 ± 15%; P < 0.001) muscle eNOS protein levels and the levels were further elevated (30 ± 10%; P < 0.01) by the subsequent 4 wk period. Four wks of continuous training enhanced the capillary to fiber ratio (C:F) (2.37 ± 0.14 to 3.00 ± 0.26 cap fiber−2; P < 0.001) with no further change after 4 wks of interval training. Capillary density was elevated (433 ± 30 to 560 ± 40 cap mm−2; P < 0.05) after the first 4 wks and was further elevated (635 ± 35 cap mm−2; P < 0.05) after 4 wks of interval training. Control group: Muscle VEGF protein levels were not altered by training whereas eNOS protein levels were increased (P < 0.001) similarly as in the intervention group. C:F increased (2.67 ± 0.22 to 3.07 ± 0.21 cap fiber−2; P < 0.05) from 0 to 8 wks. CONCLUSION: The results demonstrate that the interstitial VEGF levels in response to exercise are dependent on the exercise mode but not on training status. A change in training mode from continuous moderate to intense interval training does not further enhance capillary growth or angiogenic factors compared to continued moderate exercise training.

Effect of a 1-hour single bout of moderate-intensity exercise on fat oxidation kinetics

The present study aimed to examine the effects of a prior 1-hour continuous exercise bout (CONT) at an intensity (Fat max) that elicits the maximal fat oxidation (MFO) on the fat oxidation kinetics during a subsequent submaximal incremental test (IncrC). Twenty moderately trained subjects (9 men and 11 women) performed a graded test on a treadmill (Incr), with 3-minute stages and 1-km·h −1 increments. Fat oxidation was measured using indirect calorimetry and plotted as a function of exercise intensity. A mathematical model (SIN) including 3 independent variables ( dilatation, symmetry, and translation) was used to characterize the shape of fat oxidation kinetics and to determine Fat max and MFO. On a second visit, the subjects performed CONT at Fat max followed by IncrC. After CONT performed at 57% ± 3% (means ± SE) maximal oxygen uptake (V̇o 2max), the respiratory exchange ratio during IncrC was lower at every stage compared with Incr ( P < .05). Fat max (56.4% ± 2.3% vs 51.5% ± 2.4% V̇o 2max, P = .013), MFO (0.50 ± 0.03 vs 0.40 ± 0.03 g·min −1, P < .001), and fat oxidation rates from 35% to 70% V̇o 2max ( P < .05) were significantly greater during IncrC compared with Incr. However, dilatation and translation were not significantly different ( P > .05), whereas symmetry tended to be greater in IncrC ( P = .096). This study showed that the prior 1-hour continuous moderate-intensity exercise bout increased Fat max, MFO, and fat oxidation rates over a wide range of intensities during the postexercise incremental test. Moreover, the shape of the postexercise fat oxidation kinetics tended to have a rightward asymmetry.

Energy Expenditure And Fat Utilization During And After Interval Versus Continuous Self-paced Exercise Bouts

PURPOSE: Exercise is often performed to achieve high energy expenditure (EE) and fat oxidation (FO). The purpose of the study was to compare exercise EE, early recovery EE (REE), and total FO during self-paced "hard interval" vs "talking intensity" continuous exercise bouts typical of fitness industry exercise prescriptions. METHODS: After preliminary testing, 9 regularly active males (age 28 ± 6 yr, VO2max 55 ± 5 ml·min-1·kg-1) performed a self-paced high intensity interval session (INT) consisting of six, 4 min work bouts interspersed by 2 min recovery periods (34 min total exercise time) with continuous gas exchange measurement during the 34 min exercise session and for 30 min post exercise. Responses were compared with those measured during a "talking intensity" exercise bout of identical total duration (SS). The two bouts were performed in randomized order. EE, REE, and FO were estimated from continuous measurements of respiratory gas exchange. Fat oxidation calculations are considered minimum estimates due to presumed contamination of CO2 production with CO2 release due to H+buffering. RESULTS: The INT session elicited higher average heart rate (171 ± 14 vs 154 ± 15, p<0.001), blood lactate concentration (6.5 ± 2.8 vs 2.1 ± 1.1 mmol·L-1, p<0.001), and RPE (17 ± 1 vs 12 ± 1, p<0.001) than the SS session. EE during INT was ∼12% higher (555 ± 75 vs 495 ± 68 kcal, p<0.01) and 30min REE was 23% higher (89 ± 15 vs 72 ± 9 kcal, p<0.01). FO during 34 min exercise tended to be higher in SS (13.0 ± 5.3 vs 9.4 ± 4.5 g, p = 0.12). FO during the first 30 min post-exercise was higher after INT (4.5± 1.4 vs 2.5 ± 1.3 g. p = 0.02). Total FO (34 min exercise+30 min recovery) was similar in the interval based and continuous exercise sessions (13.0 ± 3.7 vs 15.5 ± 6.4 g, p= 0.56). CONCLUSIONS: In this study, we have attempted to simulate two exercise prescriptions typical of the time constraints and intensity goals of "1 hour fitness classes". Our results suggest that for the same time investment, self-paced interval training results in significantly greater total energy expenditure and similar total fat oxidation than continuous exercise performed at "talking intensity."

Effects of Continuous Versus Intermittent Exercise, Obesity, and Gender on Growth Hormone Secretion

Obesity attenuates spontaneous GH secretion and the GH response to exercise. Obese individuals often have low fitness levels, limiting their ability to complete a typical 30-min bout of continuous exercise. An alternative regimen in obese subjects may be shorter bouts of exercise interspersed throughout the day. The objective of the study was to examine whether intermittent and continuous exercise interventions evoke similar patterns of 24-h GH secretion and whether responses are attenuated in obese subjects or affected by gender. This was a repeated-measures design in which each subject served as their own control. This study was conducted at the University of Virginia General Clinical Research Center. Subjects were healthy nonobese (n = 15) and obese (n = 14) young adults. Subjects were studied over 24 h at the General Clinical Research Center on three occasions: control, one 30-min bout of exercise, and three 10-min bouts of exercise. Twenty-four hour GH secretion was measured. Compared with unstimulated 24-h GH secretion, both intermittent and continuous exercise, at constant exercise intensity, resulted in severalfold elevation of 24-h integrated serum GH concentrations in young adults. Basal and pulsatile modes of GH secretion were attenuated both at rest and during exercise in obese subjects. The present data suggest that continuous and intermittent exercise training should be comparably effective in increasing 24-h GH secretion.

Post-exercise hypotension and cardiovascular responses to moderate orthostatic stress in endurance-trained males

We tested the hypothesis that following an acute bout of exercise cardiovascular and cerebrovascular responses to lower-body negative pressure (LBNP) would be altered due to post-exercise hypotension (PEH). Ten healthy, male, endurance-trained athletes (mean age +/- SD = 29.6 +/- 5) were assessed for cardiovascular and cerebrovascular responses to LBNP following acute bouts of interval and continuous exercise. Mean arterial pressure (MAP), cardiac output, total peripheral resistance, heart rate variability, and total cerebral oxygen index were determined during a baseline LBNP session. These indices were also determined during two other LBNP sessions: following an acute bout of interval exercise, and following an acute bout of continuous exercise. Compared with baseline, MAP was reduced after both exercise conditions, similar to values previously reported (10 mmHg; p < 0.05 vs. pre-exercise). Total peripheral resistance was significantly reduced following both exercise bouts, and heart rate was significantly increased post-exercise (rest: 59.6 +/- 11.2; interval: 77.8 +/- 12.8; continuous: 80.3 +/- 15.2 beats.min(-1)). Both cardiac output and stroke volume responses to LBNP following exercise were not altered when compared with baseline measurements. Tissue oxygenation during -40 mmHg (interval: 74.31% +/- 7.82% vs. continuous: 69.13% +/- 5.23%) was significantly lower than during normobaric pressure (interval: 77.14% +/- 1.30% vs. continuous: 74.41% +/- 0.94%). It appears from these observations that although young, endurance-trained males experience PEH following acute bouts of interval or continuous exercise, this hypotension does not alter the cardiovascular and cerebrovascular responses to a moderate orthostatic stress.

Lactate, Fructose and Glucose Oxidation Profiles in Sports Drinks and the Effect on Exercise Performance

Exogenous carbohydrate oxidation was assessed in 6 male Category 1 and 2 cyclists who consumed CytoMax™ (C) or a leading sports drink (G) before and during continuous exercise (CE). C contained lactate-polymer, fructose, glucose and glucose polymer, while G contained fructose and glucose. Peak power output and VO2 on a cycle ergometer were 408±13 W and 67.4±3.2 mlO2·kg−1·min−1. Subjects performed 3 bouts of CE with C, and 2 with G at 62% VO2peak for 90 min, followed by high intensity (HI) exercise (86% VO2peak) to volitional fatigue. Subjects consumed 250 ml fluid immediately before (−2 min) and every 15 min of cycling. Drinks at −2 and 45 min contained 100 mg of [U-13C]-lactate, -glucose or -fructose. Blood, pulmonary gas samples and 13CO2 excretion were taken prior to fluid ingestion and at 5,10,15,30,45,60,75, and 90 min of CE, at the end of HI, and 15 min of recovery. HI after CE was 25% longer with C than G (6.5±0.8 vs. 5.2±1.0 min, P<0.05). 13CO2 from the −2 min lactate tracer was significantly elevated above rest at 5 min of exercise, and peaked at 15 min. 13CO2 from the −2 min glucose tracer peaked at 45 min for C and G. 13CO2 increased rapidly from the 45 min lactate dose, and by 60 min of exercise was 33% greater than glucose in C or G, and 36% greater than fructose in G. 13CO2 production following tracer fructose ingestion was greater than glucose in the first 45 minutes in C and G. Cumulative recoveries of tracer during exercise were: 92%±5.3% for lactate in C and 25±4.0% for glucose in C or G. Recoveries for fructose in C and G were 75±5.9% and 26±6.6%, respectively. Lactate was used more rapidly and to a greater extent than fructose or glucose. CytoMax significantly enhanced HI.

Effect of different intensities of effort on anaerobic glycolysis during continuous and intermittent exercise

Nós examinamos a influência de diferentes intensidades no comportamento do lactato e glicose sangüínea durante o exercício contínuo e intermitente. Oito sujeitos divididos em dois grupos de quatro foram submetidos a um teste para determinação do limiar anaeróbio (LA) e a cinco sessões de exercício intermitente ou contínuo a 10, 20, 30, 40 e 50% acima do LA. Posteriormente, os voluntários foram submetidos a um exercício contínuo/intermitente com intensidade de 30% acima do LA. Durante o exercício contínuo as amostras de sangue foram coletadas a cada intervalo de 5 min. Ao passo que, durante o exercício intermitente as amostras foram coletadas a cada 6 min, incluindo pausa e atividade. Os valores de freqüência cardíaca (FC) e percepção subjetiva de esforço (PSE) foram registrados concomitantemente com as coletas de sangue. Os resultados durante o exercício intermitente mostraram um aumento significativo nas concentrações de lactato para a intensidade de 50% comparado as demais intensidades (p &lt; 0,05). A glicemia aumentou significativamente para as intensidades de 20 e 50% comparado as demais intensidades (p &lt; 0,05). No exercício contínuo os aumentos nas concentrações de lactato foram significativos para as intensidades de 20, 30, 40 e 50% (p &lt; 0,05) comparado a intensidade de 10%, enquanto a glicemia se manteve estável para as diferentes intensidades (p &gt; 0,05). Comparados, o exercício intermitente produziu uma concentração de lactato significativamente menor que o exercício contínuo, seguido de uma menor captação de glicose (p &lt; 0,05). Os resultados sugerem que o exercício intermitente ao contrário do contínuo, pode ser realizado numa intensidade muito acima do LA por longo período de tempo, mantendo-se estáveis os níveis de lactato e seguido de uma menor utilização da glicose sangüínea

Using ratings of perceived exertionto reproduce blood lactate levels duringa continuous exercise bout of varying intensities

The purpose of this study was to investigate whether blood lactate concentra-tion (BLC) could be reproduced, corresponding to previously measured BLC, by using Borg's rate of perceived exertion (RPE) scale to determine exercise intensity at 3 different levels during a single 30-min exercise bout. Twelve participants (4 M, 8 F; age: 26.5 ± 3.7 years; height: 168.9 ± 8.3 cm; weight: 68.2 ± 14.1 kg) completed an RPE estimation trial (a 3-min stage incremental treadmill protocol to volitional fatigue, where RPE was noted at each stage); practiced running at the workloads corresponding to their RPE of 11, 14, and 16; and, within 2 weeks after the practice run, completed a continuous, self-selected intensity run for 10-min at each RPE target value (the production run). Paired t tests indicated that there were no significant difference (p > .05) in BLC between the estimation and production trials at RPE of 11, 14, and 16 (estima-tion trial 2.71 ± 0.83, 4.15 ± 1.78, 5.83 ± 2.09 mM, production trial 2.99 ± 1.18, 4.32 ± 2.09, 5.62 ± 1.90 mM), indicating as a group that subjects were able to successfully reproduce target BLC. There was, however, considerable intra-and inter-subject variability that warrants additional investigation before these results can be used to support RPE as a production tool for target BLC.