Exercise training at the crossover point improves bodily and cardiorespiratory data but not quality of life in women with metabolic syndrome.

BACKGROUND: This study investigated the effects of an exercise program at the intensity corresponding to the crossover point of substrate utilization (COP) on anthropometric measures, health-related quality of life (HRQoL) and cardiorespiratory fitness (i.e., peak oxygen uptake [V̇O2peak] and peak power output [Ppeak]) in women with metabolic syndrome (MetS). METHODS: Nineteen obese and post-menopausal women with MetS (age: 54.8±8.1 years, body mass: 89.0±12.2 kg, Body Mass Index: 34.5±4.0 kg/m2) followed a 12-week program consisting of three 45-minute sessions per week of cycle ergometer exercise. The imposed exercise intensity corresponded to COP. Before and after the program, HRQoL, V̇O2peak and Ppeak were measured and then compared. RESULTS: Body mass (89.0±12.2 vs. 86.2±11.0 kg), Body Mass Index (34.5±4.0 vs. 33.4±3.6 kg/m2), waist (106±10 vs. 100±9 cm) and hip (117±11 vs. 114±11 cm) circumferences, waist-to-hip ratio (0.91±0.07 vs. 0.88±0.07), fat mass (43.3±4.6 vs. 41.9±4.6%), fat-free mass (56.7±4.6 vs. 58.2±4.6%), V̇O2peak (16.6±3.4 vs. 18.1±4.1 mL/min/kg) and Ppeak (102±22 vs. 125±27 W) were significantly improved after the exercise program (P<0.05), but HRQoL showed no significant improvement on any subscale (i.e., physical functioning: performance limitation for physical activities including bathing and dressing, role physical: problems with work or other daily activities, bodily pain, general health, vitality, social functioning, role emotional and mental health; P>0.05). CONCLUSIONS: Although a 12-week exercise program at COP improved anthropometric measures and cardiorespiratory fitness in women with MetS, self-perceived HRQoL did not significantly improve. This finding may be linked to a significant but still insufficient reduction in body mass, probably because COP is too weak exercise intensity to induce important energy expenditure.

Correlation of gas exchange threshold and first muscle oxyhemoglobin inflection point with time-to-exhaustion during heavy-intensity exercise.

BACKGROUND: The twofold aim of the study was to: 1) compare the gas exchange threshold (GET), the first oxyhemoglobin inflection point ([O2Hb]-T), and perceptual threshold as determined during an incremental exercise test, and 2) investigate the link between each threshold and time-to-exhaustion during heavy intensity exercise. METHODS: Fourteen competitive cyclists performed an incremental exercise test to exhaustion on a cycloergometer to determine the different thresholds and peak workload (Wpeak). The participants then performed a sub-maximal constant workload test (90% Wpeak) to exhaustion to determine time-to-exhaustion. The thresholds were identified from: 1) the first breakpoint in the oxygen uptake vs. carbon dioxide output curve (GET), 2) the [O2Hb]-T, and 3) a rating of 13 in perceived exertion (perceptual threshold: RPE13-T). RESULTS: Oxygen uptake at the different thresholds was not significantly different (P>0.05). Moreover, GET and [O2Hb]-T were significantly correlated: 1) to each other (r≥0.79; P≤0.001), and 2) to time-to-exhaustion (r=0.81 and r=0.72, respectively; P<0.01). RPE13-T, however, was not significantly correlated with the time-to-exhaustion (P=0.148). CONCLUSIONS: The anaerobic threshold as identified from GET was concomitant to [O2Hb]-T. Both thresholds were correlated to time-to-exhaustion, and could therefore be used as a performance index in middle-duration events.

Effects of Endurance Training at the Crossover Point in Women with Metabolic Syndrome.

INTRODUCTION: On the basis of theoretical evidence, intensity at the crossover point (COP) of substrate utilization could be considered as potential exercise intensity for metabolic syndrome (MetS). This study aimed to examine the effects of a training program at COP on exercise capacity parameters in women with MetS and to compare two metabolic indices (COP and the maximal fat oxidation rate point LIPOXmax®) with ventilatory threshold (VT). METHODS: Nineteen women with MetS volunteered to perform a 12-wk training program on a cycle ergometer, with intensity corresponding to COP. Pre- and posttraining values of anthropometric and exercise capacity parameters were compared to determine the effects of exercise training. The pre-post training change of COP, LIPOXmax®, and VT were also investigated. RESULTS: After training, anthropometric parameters were significantly modified, with reduction of body mass (3.0% ± 3.0%, P < 0.001), fat mass (3.3% ± 3.4%, P < 0.001), and body mass index (3.2% ± 3.4%, P < 0.001). Exercise capacity was improved after the training program, with significant increase of maximal power output (25.0% ± 18.4%, P < 0.001) and maximal oxygen uptake (V˙O2max, 9.0% ± 11.2%; P < 0.01). Lastly, when expressed in terms of power output, COP, LIPOXmax®, and VT occurred at a similar exercise intensity, but the occurrence of these three indices is different when expressed in terms of oxygen uptake, HR, or RPE. CONCLUSIONS: This study highlights the effectiveness of a 12-wk training program at COP to improve physical fitness in women with MetS. The relations between metabolic indices and VT in terms of power output highlight the determination of VT from a shorter maximal exercise as a useful method for determining metabolic indices in MetS.

Prediction of maximal or peak oxygen uptake from ratings of perceived exertion.

Maximal or peak oxygen uptake (V˙O2 max and V˙O2 peak , respectively) are commonly measured during graded exercise tests (GXTs) to assess cardiorespiratory fitness (CRF), to prescribe exercise intensity and/or to evaluate the effects of training. However, direct measurement of CRF requires a GXT to volitional exhaustion, which may not always be well accepted by athletes or which should be avoided in some clinical populations. Consequently, numerous studies have proposed various sub-maximal exercise tests to predict V˙O2 max or V˙O2 peak . Because of the strong link between ratings of perceived exertion (RPE) and oxygen uptake (V˙O2), it has been proposed that the individual relationship between RPE and V˙O2 (RPE:V˙O2) can be used to predict V˙O2 max (or V˙O2 peak) from data measured during submaximal exercise tests. To predict V˙O2 max or V˙O2 peak from these linear regressions, two procedures may be identified: an estimation procedure or a production procedure. The estimation procedure is a passive process in which the individual is typically asked to rate how hard an exercise bout feels according to the RPE scale during each stage of a submaximal GXT. The production procedure is an active process in which the individual is asked to self-regulate and maintain an exercise intensity corresponding to a prescribed RPE. This procedure is referred to as a perceptually regulated exercise test (PRET). Recently, prediction of V˙O2max or V˙O2 peak from RPE:V˙O2 measured during both GXT and PRET has received growing interest. A number of studies have tested the validity, reliability and sensitivity of predicted V˙O2 max or V˙O2 peak from RPE:V˙O2 extrapolated to the theoretical V˙O2 max at RPE20 (or RPE19). This review summarizes studies that have used this predictive method during submaximal estimation or production procedures in various populations (i.e., sedentary individuals, athletes and pathological populations). The accuracy of the methods is discussed according to the RPE:V˙O2 range used to plot the linear regression (e.g., RPE9­13 versus RPE9­15 versus RPE9­17 during PRET), as well as the perceptual endpoint used for the extrapolation (i.e., RPE19 and RPE20). The V˙O2 max or V˙O2 peak predictions from RPE:V˙O2 are also compared with heart rate-related predictive methods. This review suggests that V˙O2 max (or V˙O2 peak ) may be predicted from RPE:V˙O2 extrapolated to the theoretical V˙O2 max (or V˙O2 peak) at RPE20 (or RPE19). However, it is generally preferable to (1) extrapolate RPE:V ˙ O 2 to RPE19 (rather than RPE20); (2) use wider RPE ranges (e.g. RPE ≤ 17 or RPE9­17) in order to increase the accuracy of the predictions; and (3) use RPE ≤ 15 or RPE9­15 in order to reduce the risk of cardiovascular complications in clinical populations.

Estimated time limit: a brief review of a perceptually based scale.

The ability to predict performance is of great interest for athletes and coaches. It is helpful for the selection of athletes to a team, the prescription of individualized training and the determination of the optimal pacing strategy. However, it is often difficult to judge the time to exhaustion without maximal exercise testing, which is often difficult to schedule during a competitive season. Consequently, the purpose of this review is to present a recent tool based on subjective prediction of time to exhaustion than can be achieved without requiring a maximal effort. This tool is the estimated time limit (ETL) scale. This review summarizes all experimentations that have studied the ETL scale. These studies suggest that the ETL scale may be used to predict time to exhaustion.

Prediction of time to exhaustion in competitive cyclists from a perceptually based scale.

Prediction of time to exhaustion in competitive cyclists from a perceptually based scale. We have tested the validity of the estimated time limit (ETL) scale to predict an exhaustion time (T(lim)) from values stemming from incremental and randomized constant workloads tests on a cycle ergometer. Twenty-five cyclists performed 1 continuous incremental test, 1 discontinuous test with randomized workloads, and 1 constant power output test at 90% of maximal aerobic power (MAP) to exhaustion. Estimated time limits at 90% MAP during the incremental test and the test with randomized workloads were calculated from exponential relationships between power and ETL using the same 4 workloads. Real measured T(lim) during the constant power output test was converted into ETL values (called measured ETL). The differences between the calculated and measured ETLs were examined. Estimated time limits calculated at 90% MAP during the incremental and randomized tests corresponded to 14 minutes 56 seconds and 10 minutes 14 seconds, whereas measured ETL was equal to 11 minutes 19 seconds ± 3 minutes 40 seconds. The results showed a nonsignificant difference between calculated and measured ETLs. However, the mean differences between the measured ETL values during the constant test performed at the same intensity were -1.3 ± 2.9 and 0.3 ± 3.0 for the incremental and the randomized constant workloads tests, respectively. Consequently, the use of ETL calculated at 90% MAP during the test with randomized constant workloads may be preferable to predict the accurate T(lim). Moreover, it would seem that high-level cyclists, who were more consciously attuned to their bodies and their own effort sense, were more accurate in their prediction than low-level cyclists. It is concluded that the randomized constant workloads test that is both shorter and less strenuous would be more convenient for high-level athletes.

Prediction of peak oxygen uptake from age and power output at RPE 15 in obese women.

The purpose of this study was to develop a simple, convenient and indirect method for predicting peak oxygen uptake (VO2peak) from a sub-maximal graded exercise test (GXT), in obese women. Thirty obese women performed GXT to volitional exhaustion. During GXT, oxygen uptake and the power at RPE 15 (VO2peak) were measured, and VO2peak was determined. Following assessment of the relationships between VO2peak and PRPE 15, age, height and mass were made available in a stepwise multiple regression analysis with VO2peak as the dependent variable. The equation to predict VO2peak was: (1 min-1) = 1.355 - 9.920e-3 x age + 8.497e-3 x PRPE 15 (r = 0.83; SEE = 0.156 l min(-1)). This study suggests that age and PRPE 15 elicited during a sub-maximal GXT provides a reasonably accurate prediction of VO2peak in obese women.

Athletes' dietary intake was closer to French RDA's than those of young sedentary counterparts.

It has been demonstrated that athletes' dietary intake was relatively well-balanced according to the recommended dietary allowances (RDAs). In contrast, other studies have shown that athletes may have low energy intake or imbalance of protein and fat and insufficient minerals and vitamins. Nonetheless, we hypothesized that practicing a sport may allow young adults to have a nutritional status closer to recommended values. The purpose of this experiment was to study the nutritional status of young French adults, particularly to compare the nutritional status of trained young male and female athletes to those of young sedentary control subjects, and to national RDAs. A total of 85 young adults were recruited and filled a 4-day food and physical activity record. Dietary intake, energy expenditure, energy balance, carbohydrate, protein, fat, water, vitamins, and minerals were recorded. Data were analyzed with a software Nutrilog and statistics with Sigma Stat. Energy intake values were 9874 +/- 3050 kJ for the athletes and 7506 +/- 1845 kJ for control subjects. Athletes' nutritional status was closer to French RDAs than those of sedentary subjects who present a lower energy intake, a greater percentage of the energy intake from fat and lower values for minerals and vitamins. In conclusion, practicing a sport may allow athletes to balance their energy intake and expenditure and could be a good way to have a nutritional status closer to RDAs. Educational programs for students on proper food selection, eating habits and physical activity are needed to improve the nutritional status of these young French adults, particularly in sedentary students.

Prediction of peak oxygen uptake from sub-maximal ratings of perceived exertion elicited during a graded exercise test in obese women.

The purpose was to assess the validity of predicting peak oxygen uptake (.VO(2)peak) from Ratings of Perceived Exertion (RPE)< or =15, during a graded exercise test (GXT), in obese women. Forty-three obese women performed GXT to volitional exhaustion. During GXT, oxygen uptake (.VO(2)) and RPE were measured. Individual linear regressions between .VO(2) and RPE< or =15 were extrapolated to RPE 20 in order to predict .VO(2)peak. Actual and predicted .VO(2)peak were not significantly different (13.9+/-3.0 vs 14.2+/-3.3 ml kg(-1) min(-1), respectively; p=.26). The Pearson product moment correlation between actual and predicted .VO(2)peak was high (r=0.82). The 95% limits of agreement analysis on these values (bias+/-1.96SD) was -0.3+/-3.7 ml kg(-1) min(-1). Results suggested that RPE< or =15 elicited during a sub-maximal GXT provides accurate .VO(2)peak prediction. Therefore, it is not necessary to perform GXT to voluntary exhaustion to determine .VO(2)peak in obese women.

Influence of successive bouts of fatiguing exercise on perceptual and physiological markers during an incremental exercise test.

The purpose of this study was to examine the effects of a succession of fatiguing stages, on ratings of perceived exertion (RPE) and estimated time limits (ETL) during an incremental exercise test. Twenty-seven cyclists performed a continuous incremental test and a discontinuous test with randomized workloads. A linear mixed model was used to compare the RPE, ETL, respiratory gas, heart rate, and blood data obtained during the two exercise tests. RPE and ETL were not significantly different between the tests. Ventilation, breathing frequency, heart rate, and blood lactate concentration were significantly higher during the last incremental test workloads. In conclusion, although the incremental exercise test generated higher cardiorespiratory and muscular workloads than observed during the randomized exercise test, most likely due to a greater fatiguing process, these higher workloads did not influence the perceptual response.

Intermittent versus continuous exercise: effects of perceptually lower exercise in obese women.

INTRODUCTION: Exercise has beneficial effects on obesity and diabetes treatments. However, obese subjects do not closely adhere to training programs probably because of the monotony of the continuous exercise that is frequently proposed. To increase adherence to training programs, intermittent exercise, which is less monotonous, may be more appropriate. PURPOSE: The purposes of this study were to determine the perceptually less hard exercise (continuous vs intermittent exercise) and to analyze the impact of a training program on the basis of this exercise in obese women with and without type 2 diabetes. METHODS: Twenty type 2 diabetic obese women and 20 obese women without diabetes were recruited. In each group, 10 patients integrated a training program (i.e., training groups), whereas the remaining patients were untrained (i.e., control groups). The training groups performed a continuous exercise and an intermittent exercise to determine the perceptually less hard exercise thanks to lower ratings of perceived exertion (RPE). Then, a training program that included 32 min (3 d x wk(-1) x 10 wk(-1)) of the perceptually less hard exercise was proposed to training groups. RESULTS: RPE were significantly lower during the intermittent exercise compared to the continuous exercise in the obese women with or without diabetes (RPE = 12.3 +/- 2.3 vs 13.7 +/- 2.3 and RPE = 11.9 +/- 1.1 vs 13.2 +/- 1.6, respectively). After the training program, significant beneficial effects on the glycosylated hemoglobin (6.8 +/- 1.4% vs 6.5 +/- 1.2%), body mass (97.1 +/- 16.9 vs 95.2 +/- 16.2 kg), body mass index (37.6 +/- 6.1 vs 36.8 +/- 6.0 kg x m(-2)), and on the HR and the walked distance limit were noticed in the training groups. CONCLUSION: The obese women with or without diabetes perceived the intermittent exercise as being less hard than the continuous exercise, and a training program based on intermittent exercises produced beneficial effects on obesity and type 2 diabetes.

Objective and subjective analysis of the training content in young cyclists.

The purpose of this study was to analyse the objective and subjective training for young cyclists that is prescribed by their coaches. Seven cyclists performed an incremental exercise to exhaustion before and after 14 weeks of training using an incremental test to determine their maximal oxygen uptake (VO(2) (max)), the velocity associated with VO(2) (max) (vVO(2) (max)), and the velocity associated with the ventilatory threshold (vVT). Cyclists completed a training record with the actual content and the perceived exertion of each training session during these 14 weeks. We have focused on the actual content of the training prescribed by the coaches. Analysis of the content of each session allowed us to calculate the objective training load (volume at different intensities) and to determine the subjective training load from perceived exertion ratings (training load, monotony, strain, and fitness-fatigue). The results showed that cyclists were training at a relatively low intensity and that training rating of perceived exhaustion was weak. Moreover, after 14 weeks of training, VO2 max did not change whereas vVO(2) (max) and vVT increased significantly. Therefore, a discrepancy may exist between what is perceived during training and the effects of training. Consequently, objective and subjective indices collected from training books provided useful information supplementary to that recorded from the physiological indices alone.

Effect of incremental and submaximal constant load tests: protocol on perceived exertion (CR10) values.

The purpose of the present investigation was to determine to what extent the protocol (incremental and constant load exercises) affects the ratings of perceived exertion for a given submaximal intensity on a cycle ergometer. 10 healthy and well-trained male students (M age=23 yr., SD=2.9) performed an incremental exercise to determine maximal oxygen uptake (VO2 max), maximal aerobic power, and the ratings of perceived exertion (CR10) corresponding to 70% and 75% VO2 max (CR10(70i) and CR10(75i)). Two 30-min. constant load exercises set at these intensities were performed to establish the corresponding CR10 values. CR10(70i) (5.6 +/- 1.9) and CR10(75i) (6.2 +/- 1.9) were significantly higher than all CR10 values collected at Minutes 5, 10, 15, 20, 25, and 30 of the constant load exercises. These results indicate that, for a given exercise intensity (70% and 75% VO2 max), subjects are rated higher during an incremental exercise than during a 30-min. submaximal constant load test. Therefore, when coaches and physiotherapists want to use CR10 values reported during an incremental standard exercise to set training loads, they have to be prudent since the same relative exercise intensity does not seem to be perceived identically during a submaximal constant exercise as during an incremental one.