The reliability and validity of regulating exercise intensity by ratings of perceived exertion in step dance sessions

The purpose of this study was to determine the reliability and validity of regulating exercise intensity by ratings of perceived exertion in step dance sessions. Ten male college-aged students voluntarily participated in 2 step dance sessions for 45 minutes at 70-80% of their heart rate (HR) reserves with a 1-week interval between sessions. The step dance sessions included the same choreography with 10 minutes of warm-up, 25 minutes of the main part, 5 minutes of calisthenics for legs and abdomen, and 5 minutes of cool-down. In each session, subjects' ratings of perceived exertion (RPEs) were determined by Borg's 6-20 scale together with HR and lactic acid (LA) levels with 10-minute intervals. Values for RPE, HR, and LA increased nonlinearly in both sessions, and their trends were explained by polynomial equations to the second degree. The RPE values increased throughout each session, whereas HR and LA showed a decrease in the last time interval, which indicated that RPE did not maintain exercise intensity at proper range. Reliability coefficients for RPE scores in the first and last session ranged from 0.602 to 0.684. These findings suggest that RPE was a reliable but not a valid method for regulating exercise intensity in step dance sessions.     

Postural control in healthy young adults using a double seesaw device

Postural control on single and double seesaws was investigated in young healthy adults required to stand as still as possible on two side-by-side seesaws favoring pitch motion and lying on two separate force platforms. The device offers the possibility to get associated or dissociated seesaws and, if dissociated, to induce asymmetric patterns for the centers-of-pressure (CP) under both left and right feet by using different radii for the two seesaws. Substituting a parallelepiped volume to one seesaw offering a firm contact to one foot is also possible. The results indicated that dissociating the two seesaws led to increased resultant CP (CP_Res) and vertically projected center-of-gravity movements (CG_v) only along the mediolateral axis, whereas a slight decreasing tendency characterized these movements along the antero-posterior axis. When standing on two independent seesaws with different radii, significantly larger CP displacements were seen along the antero-posterior axis under the foot lying on the more stable support, i.e., the seesaw with the longer radius or the parallelepiped volume. In these two asymmetrical conditions, the CP_Res output results from a compensatory mechanism, i.e. larger movements under one foot to compensate for the decreased movements occurring under the opposite foot. This postural control strategy is aimed at allowing sufficient CP_Res displacements in order to appropriately secure balance. Because of the complex sensorimotor coordination induced, involving differentially in certain cases both legs, the double seesaw device can be viewed as a possible tool for challenging postural control by inducing asymmetrical patterns between left and right feet CP movements.     

Differentiated ratings of perceived exertion at ventilatory threshold in children and adults

The purpose of this study was to examine overall, leg and chest ratings of perceived exertion (RPE) at ventilatory threshold (Th_vent) in 16 children (mean age 10.9 years) and 17 adults (mean age 24.3 years). Th_vent and maximum oxygen consumption (V˙O_{2 max} ) were measured during a graded exercise test on a cycle ergometer. Overall, leg and chest RPE were obtained at the end of each exercise stage. V˙O_{2 max} was 49.9 (8.5) and 47.1 (6.1) ml · kg⁻¹· min⁻¹ [mean (SD)] in the adults and children, respectively (P > 0.05). Relative to V˙O_{2 max} , Th_vent was 61.7 (5.3)% in the adults and 64.7 (5.2)% in the children (P > 0.05). Overall, leg, and chest RPE values at Th_vent for the adults were 11.5 (2.6), 11.9 (2.5), and 10.5 (2.5), while for the children these values were 13.6 (2.2), 14.1 (2.2), and 12.6 (2.3), respectively. All RPE values were higher for the children (P < 0.05). These results suggest that children are able to discriminate levels of exertion in different parts of their body during graded exercise. Furthermore, children rate an intensity corresponding to Th_vent to require a greater overall, leg and chest effort than adults exercising at a similar intensity. This indicates that children experience more pronounced cardiorespiratory and muscular sensations during this type of exercise. Accepted: 19 February 1998     

Validity of heart rate and ratings of perceived exertion as indices of exercise intensity in a group of children while swimming.

The purpose of this study was to investigate the validity of heart rate (fc) and ratings of perceived exertion (RPE) as indices of exercise intensity in a group of children while swimming. Six healthy male swimmers, aged 10-12, swam tethered using the breast-stroke in a flume. The resistance started at 1.0 kg and increased in 1.0 kg steps up to the point of their exhaustion. The subjects swam for 5 min during each period, with a rest of 10-20 min until they had returned to their resting fc level. The last exercise intensity was with the maximal mass the subjects could support for 2 min. The last min of oxygen consumption (VO2) and 30 s of fc were measured during each exercise period. The subjects gave their RPE assessment at the end of exercise. The individual relationships between fc and VO2, and percentage maximal oxygen consumption (%VO2max) were linear with a high correlation r = 0.962-0.996 and r = 0.962-0.996, respectively. Therefore, it was concluded that fc was valid as an index of the exercise intensity of children while swimming. Compared to the results found in adults using a similar protocol, the children's fc were 8.3-26.9 beats.min-1 higher than those of the adults at the given %VO2max. The present study showed two different patterns in the relationship between VO2 and RPE in individuals. In two subjects the RPE increased linearly with VO2 while in the other four subjects the increase was discontinuous. If fc and RPE were to be applied to the setting and evaluation of exercise intensity during swimming, it would seem that fc would be a more useful guide than RPE for some children.     

Gender governs the relationship between exercise intensity and growth hormone release in young adults.

We previously reported that in young adult males growth hormone (GH) release is related to exercise intensity in a linear dose-response manner (Pritzlaff et al. J Appl Physiol 87: 498-504, 1999). To investigate the effects of gender and exercise intensity on GH release, eight women (24.3 +/- 1.3 yr, 171 +/- 3.2 cm height, 63.6 +/- 8.7 kg weight) were each tested on six randomly ordered occasions [1 control condition (C), 5 exercise conditions (Ex)]. Serum GH concentrations were measured in samples obtained at 10-min intervals between 0700 and 0900 (baseline) and 0900 and 1300 (Ex + recovery or C). Integrated GH concentrations (IGHC) were calculated by trapezoidal reconstruction. During Ex, subjects exercised for 30 min (0900-0930) at one of the following intensities [normalized to the lactate threshold (LT)]: 25 and 75% of the difference between LT and rest, at LT, and at 25 and 75% of the difference between LT and peak O2 uptake. No differences were observed among conditions for baseline IGHC. To determine whether total (Ex + recovery) IGHC changed with increasing exercise intensity, slopes associated with individual linear regression models were subjected to a Wilcoxon signed-rank test. To test for gender differences, data in women were compared with the previously published data in men. A Wilcoxon ranked-sums two-tailed test was used to analyze the slopes and intercepts from the regression models. Total IGHC increased linearly with increasing exercise intensity. The slope and intercept values for the relationship between total IGHC and exercise intensity were greater in women than in men. Deconvolution analysis (0700-1300 h) revealed that, regardless of gender, increasing exercise intensity resulted in a linear increase in the mass of GH secreted per pulse and summed GH production rate, with no changes in GH secretory pulse frequency or apparent half-life of elimination. Exercise reduced the half-duration of GH secretory burst in men but not in women. Gender comparisons revealed that women had greater basal (nonpulsatile) GH secretion across all conditions, more frequent GH secretory pulses, a greater GH secretory pulse amplitude, a greater production rate, and a trend for a greater mass of GH secreted per pulse than men. We conclude that, in young adults, the GH secretory response to exercise is related to exercise intensity in a linear dose-response pattern. For each incremental increase in exercise intensity, the fractional stimulation of GH secretion is greater in women than in men.     

Haemodynamic response to exercise in healthy young and elderly subjects

Whereas with advancing age, peak heart rate (HR) and cardiac index (CI) are clearly reduced, peak stroke index (SI) may decrease, remain constant or even increase. The aim of this study was to describe the patterns of HR, SI, CI, arteriovenous difference in oxygen concentration (C _a-vO₂), mean arterial pressure (MAP), systemic vascular resistance index (SVRI), stroke work index (SWI) and mean systolic ejection rate index (MSERI) in two age groups (A: 20–30 years, n = 20; B: 50–60 years n = 20. After determination of pulmonary function, an incremental bicycle exercise test was performed, with standard gas-exchange measurements and SI assessment using electrical impedance cardiography. The following age-related changes were found: similar submaximal HR response to exercise in both groups and a higher peak HR in A than in B[185 (SD 9) vs 167 (SD 14) beats · min⁻¹, P < 0.0005]; increase in SI with exercise up to 60–90 W and subsequent stabilization in both groups. As SI decreased towards the end of exercise in B, a higher peak SI was found in A [57.5 (SD 14.0) vs 43.6 (SD 7.7) ml · m⁻², P < 0.0005]; similar submaximal CI response to exercise, higher peak CI in A [10.6 (SD 2.5) vs 7.2 (SD 1.3) l · min⁻¹ · m⁻², P < 0.0005]; no differences in C _a-vO₂ during exercise; higher MAP at all levels of exercise in B; higher SVRI at all levels of exercise in B; lower SWI in B after recovery; higher MSERI at all levels of exercise in A. The decrease in SI with advancing age would seem to be related to a decrease in myocardial contractility, which can no longer be compensated for by an increase in preload (as during submaximal exercise). Increases in systemic blood pressure may also compromise ventricular function but would seem to be of minor importance. Accepted: 24 September 1996     

Physical exercise capacity is associated with coronary and peripheral vascular function in healthy young adults

Short-term exercise training has been shown to improve cardiovascular function, whereas long-term effects of a physically active lifestyle, on coronary artery function in particular, are still not well studied. We explored possible relationships between physical exercise capacity and coronary and peripheral vascular function in healthy young adults. Twenty-nine healthy young male and female volunteers participated in the study. They underwent 1) basic clinical and echocardiographic characterization, 2) coronary flow velocity reserve (CFVR) measurement of the left anterior descending coronary artery (LAD), 3) common carotid artery (CCA) intima-media thickness (IMT) measurement, 4) assessment of CCA stiffness index (SI), 5) forearm flow-mediated vasodilation (FMD), and 6) submaximal exercise test. The calculated weight-adjusted maximal oxygen uptake capacity (Vo(2 max)(c)) was positively correlated to LAD CFVR and inversely correlated to IMT and SI. Also, subjects with high compared with moderate exercise capacity had higher FMD. In addition, subjects with LAD CFVR in the upper median had greater ratios between endothelium-dependent and -independent vasodilation in the forearm and lower SI in CCA. High exercise capacity due to a physically active lifestyle is associated with high coronary and peripheral artery function, indicating an early protective role of physical exercise for cardiovascular health.     

Small,movement dependent perturbations substantially alter postural control strategy in healthy young adults

Postural control is commonly investigated by observing responses to perturbations. We developed a perturbation paradigm mimicking self-generated errors in weight shifting, which are a common cause of falling among older adults. Our aim was to determine the effects of this small, but complex, perturbation on postural sway of healthy young adults and evaluate the role of vision and cognition during movement dependent perturbations. Fifteen participants stood hip-width apart with their eyes open, closed and while performing two different cognitive tasks. Participants were continuously perturbed by medial-lateral (ML) support surface translations corresponding to, and hence doubling, their own center of mass sway. We analyzed the standard deviation (SD), root mean square (RMS), range, and mean power frequency (MPF) of center of pressure displacements. ML postural sway increased due to the perturbation (SD p ≤ .001, range p < .001, RMS p ≤ .001, MPF p < .001). Cognitive load increased the ML sway range (p = .048). Lack of vision increased ML MPF (p = .001) and anterior-posterior (AP) range (p < .001), SD (p < .001), and RMS (p = .001). Significant interaction of vision with the perturbation was found for the ML range (p = .045) and AP SD (p = .018). The perturbation specifically affected ML postural sway. Increased MPF is indicative of a postural control strategy change, which was insufficient for fully controlling the increased sway. Despite being small, this type of perturbation appears to be challenging for young adults.     

Respiratory effort sensation during exercise with induced expiratory-flow limitation in healthy humans

Kayser, Bengt, Pawel Sliwinski, Sheng Yan, Mirek Tobiasz,and Peter T. Macklem. Respiratory effort sensation during exercisewith induced expiratory-flow limitation in healthy humans. J. Appl. Physiol. 83(3): 936-947, 1997.Nine healthy subjects (age 31 ± 4 yr) exercised with andwithout expiratory-flow limitation (maximal flow ~1 l/s). Wemonitored flow, end-tidal PCO₂, esophageal (Pes) and gastric pressures, changes in end-expiratory lungvolume, and perception (sensation) of difficulty in breathing. Subjectscycled at increasing intensity (+25 W/30 s) until symptom limitation.During the flow-limited run, exercise performance was limited in allsubjects by maximum sensation. Sensation was equally determined byinspiratory and expiratory pressure changes. In both runs, 90% of thevariance in sensation could be explained by the Pes swings (differencebetween peak inspiratory and peak expiratory Pes). End-tidalPCO₂ did not explain any variance insensation in the control run and added only 3% to the explained variance in the flow-limited run. We conclude that in healthy subjects,during normal as well as expiratory flow-limited exercise, the pleuralpressure generation of the expiratory muscles is equally related to theperception of difficulty in breathing as that of the inspiratorymuscles.

     

The effect of exercise intensity on hematuria in healthy male runners

The purpose of this study were: (1) to establish the prevalence of exercise-induced hematuria in a group of otherwise healthy male runners (n = 70), and (2) to investigate the role of exercise intensity in those runners who exhibited exercise-related hematuria (n = 10) by evaluating the effect of running and cycling at high and low intensities. The identified and recruited subjects participated in four different exercise protocols: (1) a 60-min treadmill run (RUN) at 90% of anaerobic threshold (Th_ae), (2) a 60-min leg cycle ergometer ride (BIKE) at 90% of Th_ae, (3) a 3×400-m sprint (SPRINT), each followed by 4 min of rest or light walking, and (4) 3×60-Wingate leg cycle ergometry tests, each followed by 4 min of rest or light cycling. The study employed a 3×4 (time by protocol) within-subjects design and dependent variables were measured before exercise, 4 min after, and 1 h after exercise, and included measurements of hematuria, proteinuria, urinary pH, serum haptoglobin concentration, serum creatine phosphokinase activity, plasma lactate concentration, and hemoglobin. The 400-m sprint at maximal effort significantly increased both hematuria and proteinuria (P < 0.01). Post-exercise hematuria for the SPRINT protocol was significantly different than that for the BIKE (P < 0.01) and RUN (P < 0.01) protocols. Due to the significant increase in hematuria and proteinuria following the SPRINT protocol, it was concluded that exercise-related changes in renal function were associated with weight-bearing exercise intensity rather than non-weight-bearing exercise duration. Accepted: 30 April 1998     

Wearing shoes increasing dorsiflexion improves short-term but not long-term balance control in young healthy adults

Wearing sport shoes inducing ankle dorsiflexion has been shown to alter the biomechanical specificities of the stretched muscles. The possible effect over the short and long term upon the sensorial capacities induced by such stretching has not been addressed yet. Fourteen healthy individuals were involved to assess the proprioceptive repercussion and their effects upon postural control strategies. Postural control and proprioceptive assessment were measured twice: when receiving sport shoes inducing ankle dorsiflexion and 18 days later. Proprioceptive effects were assessed using an ad-hoc device through which the seated and blindfolded subjects were required to reposition their feet in a starting position after the ankles were passively displaced to dorsiflexed and plantarflexed positions. Center-of-gravity horizontal displacements (CG_v), estimated from center-of-pressure (CP) displacements, and CP–CG_v displacements were measured through a force platform during upright quiet stance maintenance. The initial session was recorded with the subjects barefoot and wearing the shoes with a set of chocks with 0° (horizontal) and −5° (dorsiflexion) tilting angles. The second session included only barefoot performance in horizontal and dorsiflexion conditions. Dorsiflexion had no immediate effect on the postural control strategies along the anteroposterior axis. In contrast, barefoot or wearing shoes, stability was increased along the mediolateral axis during the dorsiflexion conditions. No ankle proprioceptive or postural change was observed after wearing the shoes for 18 days. Wearing dorsiflexion sport shoes induces short-term effects probably by inducing a backward tilt of the pelvis. A muscular adaptation likely prevents this effect from being prolonged.     

Factors affecting postural stability of healthy young adults

The objective of this paper was to examine the relationship between body balancing functions and body characteristics, motor abilities and reaction time. Subjects were 33 university students and 11 professional basketball players sorted into four groups of athletic and non-athletic women and men. Each group consisted of eleven subjects. The body height, weight was measured and the body mass index (BMI) calculated. A bioelectrical device computed the body fat (%). Static and dynamic motor tests, as well as static and dynamic balance tests were used. The reaction time (RT) to sound and light stimuli was measured. The regression analysis of the data revealed significant linear relationship between the amplitude of body sways (BS) and BMI in all groups. Also high correlation was found between back muscle strength and BS in all groups except the non-athletic women. Negative correlation was found between endurance capacity and BS in basketball players, i.e. at higher endurance capacity smaller amplitude BS occurred (r = -0.620, p < 0.04). The RT values showed significant correlations with BS only in the basketball players (r = 0.620, p < 0.04). It is concluded that increase in BMI, back muscle strength and endurance capacity is associated with better postural stability. Some motor abilities (hip flexibility, vertical jumping) show no significant correlations with body balancing, while other motor performances (static hanging) and RT values correlate well with BS only in the well-trained elite basketball players.     

Estimation of oxygen uptake from heart rate and ratings of perceived exertion in young soccer players

The objective of this study was to estimate the oxygen uptake (&OV0312;O2) in elite youth soccer players using measures of heart rate (HR) and ratings of perceived exertion (RPEs). Forty-six regional-level male youth soccer players (～13 years) participated in 2 VO(2)max tests. Data for HR, RPE, and VO(2) were simultaneously recorded during the VO(2)max tests with incremental running speed. Regression equations were derived from the first VO(2)max test. Two weeks later, all players performed the same VO(2)max test to validate the developed regression equations. There were no significant differences between the estimated values in the first test and actual values in the second test. During the continuous endurance exercise, the combination of percentage of maximal HR (%HRmax) and RPE measures gave similar estimation of %VO(2)max (R = 83%) in comparison to %HRmax alone (R = 81%). However, the estimation of VO(2) using combined %HRmax and RPE was not satisfactory (R = 45-46%). Therefore, the use of %HRmax (without RPE) to estimate %VO(2)max could be a useful tool in young soccer players during field-based continuous endurance testing and training. Specifically, coaches can use the %HRmax to quantify internal loads (%VO(2)max) and subsequently implement continuous endurance training at appropriate intensities. Furthermore, it seems that RPE is more useful as a measure of internal load during noncontinuous (e.g., intermittent and sprint) exercises but not to estimate %VO(2)max during continuous aerobic exercise (R = 59%).