Heart rate-index estimates oxygen uptake, energy expenditure and aerobic fitness in rugby players

The purpose of the study was to verify the suitability of heart rate-index (HRindex) in predicting submaximal oxygen consumption (VO2), energy expenditure (EE) and maximal oxygen consumption (VO2max) during treadmill running in rugby players. Fifteen professional rugby players (99.8 \ub1 12.7 kg, 1.85 \ub1 0.09 m) performed a running incremental test while VO2 (breath-by-breath) and heart rate (HR) were measured. HRindex was calculated (actual HR/resting HR) to predict submaximal and maximal VO2 ([(HRindex x 6)-5.0] x (3.5 body weight)) and EE. Measured and predicted VO2 and EE were compared by two-way RM-ANOVA (method, speed), correlation and Bland-Altman analysis. Measured and predicted VO2max were compared by paired t-test, correlation and Bland-Altman analysis. Submaximal VO2 and EE significantly increased (baseline VO2: 8.1 \ub1 1.6 ml\ub7kg-1\ub7min-1VO2max: 46.8 \ub1 4.3 ml\ub7kg-1\ub7min-1, baseline EE: 0.03 \ub1 0.01 kcal\ub7kg-1\ub7min-1, peak EE: 0.23 \ub1 0.03 kcal\ub7kg-1\ub7min-1) as a function of speed (p < 0.001 and p < 0.001 for VO2 and EE respectively) yet measured and predicted values at equal treadmill speeds were not significantly different (p = 0.17; p = 0.16) and highly correlated (r = 0.95; r = 0.94). The Bland-Altman analysis confirmed a non-significant bias between measured and estimated VO2 (measured: 40.3 \ub1 10.7, estimated: 40.7 \ub1 10.1 ml\ub7kg-1\ub7min-1, bias = 1.35 ml\ub7kg-1\ub7min-1, z = 1.12, precision = 3.39 ml\ub7kg-1\ub7min-1) and EE (measured: 20.0 \ub1 0.05 kcal\ub7kg-1\ub7min-1, estimated: 20.0 \ub1 0.05 kcal\ub7kg-1\ub7min-1, bias = 0.00 kcal\ub7kg-1\ub7min-1, z = 0.04, precision = 0.02 kcal\ub7kg-1\ub7min-1). Estimated and predicted VO2max were not statistically different (p = 0.91), highly correlated (r = 0.96), and showed a non-significant bias (bias = 0.17, z = 0.22, precision = 1.29 ml\ub7kg-1\ub7min-1). HRindex is a valid field method to track VO2, EE and VO2max during running in rugby players

Validity of a noninvasive estimation of deep body temperature when wearing personal protective equipment during exercise and recovery

©2019 The Authors. Published by BMC. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1186/s40779-019-0208-7© 2019 The Author(s). Background: Deep body temperature is a critical indicator of heat strain. However, direct measures are often invasive, costly, and difficult to implement in the field. This study assessed the agreement between deep body temperature estimated from heart rate and that measured directly during repeated work bouts while wearing explosive ordnance disposal (EOD) protective clothing and during recovery. Methods: Eight males completed three work and recovery periods across two separate days. Work consisted of treadmill walking on a 1% incline at 2.5, 4.0, or 5.5 km/h, in a random order, wearing EOD protective clothing. Ambient temperature and relative humidity were maintained at 24 °C and 50% [Wet bulb globe temperature (WBGT) (20.9 ± 1.2) °C] or 32 °C and 60% [WBGT (29.0 ± 0.2) °C] on the separate days, respectively. Heart rate and gastrointestinal temperature (TGI) were monitored continuously, and deep body temperature was also estimated from heart rate (ECTemp). Results: The overall systematic bias between TGI and ECTemp was 0.01 °C with 95% limits of agreement (LoA) of ±0.64 °C and a root mean square error of 0.32 °C. The average error statistics among participants showed no significant differences in error between the exercise and recovery periods or the environmental conditions. At TGI levels of (37.0-37.5) °C, (37.5-38.0) °C, (38.0-38.5) °C, and > 38.5 °C, the systematic bias and ± 95% LoA were (0.08 ± 0.58) °C, (-0.02 ± 0.69) °C, (-0.07 ± 0.63) °C, and (-0.32 ± 0.56) °C, respectively. Conclusions: The findings demonstrate acceptable validity of the ECTemp up to 38.5 °C. Conducting work within an ECTemp limit of 38.4 °C, in conditions similar to the present study, would protect the majority of personnel from an excessive elevation in deep body temperature (> 39.0 °C).This project was financially supported by the Australian Government, managed by the National Security Science & Technology Centre within the Defence Science & Technology Organisation, and the US Government through the Technical Support Working Group within the Combating Terrorism Technical Support Office.Published versio

A Validation Study of a Noninvasive Lactate Threshold Device

International Journal of Exercise Science 12(2): 221-232, 2019. The lactate threshold is considered a key marker of endurance exercise performance and identification of this threshold is important in writing an exercise training program. Unfortunately, assessment of the lactate threshold has traditionally required venous or capillary blood samples and a specialized meter to assess blood lactate concentrations. Recently, a consumer grade, non-invasive device was developed to determine muscle oxygenation and estimate the lactate threshold. Purpose: The aim of this study was to assess the validity of a noninvasive lactate threshold device (NID) to determine lactate threshold heart rate (LTHR). Methods: Twenty-one recreational athletes (14 females, 39 ± 7 years, 29.1 ± 5.2% fat, 37.8 ± 6.0 ml·kg-1·min-1; 7 males, 42 ± 9 years, 16.8 ± 2.2% fat, 45.9 ± 6.4 ml·kg-1·min-1) completed a personalized graded exercise test on a treadmill. All participants wore the NID and blood lactate samples were taken at the end of 3-minute stages. LTHR was then calculated using two traditional methods (4 mmol/L and \u3e1 mmol/L increase) and compared against the same heart rate values calculated by the NID. Results: No significant differences (p = .87) were found in LTHR between the NID and the traditional lactate methods (NID: 167 ± 9 bpm, 4 mmol/L: 167 ± 12 bpm, \u3e1 mmol/L: 167 ± 12 bpm). Conclusions: This study provides preliminary support for the validity of the NID for estimation of LTHR

ESTIMATING CALORIC EXPENDITURE USING THE PHYSICAL ACTIVITY INDEX (PAI) IN CHILDREN AND ADOLESCENTS PERFORMING A MULTISTAGE MAXIMAL EXERCISE TEST

PURPOSE: The primary purposes of this investigation were (a) to examine the validity of the PAI, (b) to develop a statistical model to predict cumulative Kcal expenditure using PAI as the predictor variable and (c) to develop a statistical model to predict total Kcal expenditure using PAItotal and selected physiological and behavioral measures as the predictor variables for children and adolescents performing load incremented maximal treadmill exercise. The secondary purpose of the study was to develop a prediction model to estimate total Kcal expenditure using the PAI (session) alone and in combination with selected physiological measures as the predictor variables. METHODS: Eighty-four children and adolescents (12.5±2.4 yrs) performed a maximal Bruce treadmill (TM) protocol. During TM, heart rate (HR), oxygen consumption (VO2), rating of perceived exertion (RPE-overall), pedometer step count, and Kcal expenditure were measured. Post-TM, RPE-session was obtained and a physical activity questionnaire administered. The PAI, PAItotal, and PAI (session) were calculated as: PAI = Cumulative step count x RPE-overall PAItotal = Total step count x RPE-overall at test termination PAI (session) = Total step count x RPE-session RESULTS: Multiple regression analyses revealed a strong, positive relation between the PAI score and VO2 in L.min-1(r=0.607, p<0.05), VO2 in mL.kg-1.min-1 (r=0.725, p<0.05) and HR in beats.min-1 (r=0.755, p<0.05). These findings established a high level of concurrent validity for the PAI. The following models to predict Kcal expenditure were developed: Model I : Cumulative Kcal = 21.632 + 0.006(PAI) p<0.05, SEE=17.59, r=0.74, r2=0.54. Model II : Total Kcal = -11.59+0.002(PAItotal)+27.245(VO2max) p<0.05, SEE=15.37, r=0.86, r2=0.739. Model V : Total Kcal = 38.6 + 0.004(PAIsession), p<0.05, SEE=24.23, r=0.36, r2=0.13. Model VI : Total Kcal = -64.759+26.998(VO2max)+0.305(HRmax)+0.001 (PAIsession) p<0.05, SEE=10.46, r = 0.918 , r2 = 0.842. In comparison to the PAI (session), PAI was a stronger predictor of Kcal expenditure during a load incremented treadmill protocol in a sample of children and adolescents. CONCLUSIONS: The PAI has public health implications, provides an easy tool to estimate total physical activity load (i.e. volume x intensity) and predicts Kcal expenditure in children and adolescents performing standard treadmill exercise protocols. Generalizability of findings is limited to healthy children and adolescents performing load incremented maximal treadmill exercise

Exercise prescription when there is no exercise test: the talk test

The Talk Test is a subjective measure of exercise intensity which, like RPE, has come to be accepted as an alternative to objective measures (%HRR, %VO2max) for exercise evaluation and prescription. This paper reviews the history and indications for using the Talk Test as a tool for both exercise evaluation and exercise prescription. The Talk Test, in one form or the other, has a long history, dating from at least 1937. It appears to be robust relative to the method of provoking speech and to the exercise mode. In the most widely used version, the subject recites a standard paragraph of 30-100 words, and responds to the question ‘Can you speak comfortably?’ With answers of ‘Yes’ (POSITIVE), ‘Yes, but…’ (EQUIVOCAL), and ‘No” (NEGATIVE), the Talk Test appears to be able to identify exercise intensities closely associated with the ventilatory (VT) and respiratory compensation (RCT) thresholds, and to bracket subjects into %HRR intensities closely associated with the accepted exercise/training intensity guidelines, without the need for performing a maximal exercise test. The Talk Test appears to work well in a range of populations from college students, healthy adults, elite athletes to patients with chronic diseases. It also seems to be a valid and reliable marker of the presence of exertional ischemia. In a variety of populations, the Talk Test appears capable of being translated into absolute exercise training intensities, on the basis of a commonsense step down sequence. The Talk Test appears to work by allowing detection of when the suppression of breathing frequency, which is necessary for speech, begins to lead to CO2 trapping, which interferes with breathing comfort. Its response to disrupting stimuli such as stochastic exercise, exercise training and blood donation follow predictable patterns. Guiding exercise intensity using the Talk Test instead of %HRR provides comparable responses during exercise training, without the need for an anchoring maximal exercise test. In summary, the Talk Test seems to offer a considerable promise as a means of exercise evaluation and prescription, in a wide variety of exercising individuals, without the need for a preliminary exercise test

Frame Running : enabling health improvements through physical exercise in individuals with cerebral palsy

Introduction Cerebral palsy (CP), caused by a damage to the developing brain, is the most common cause of motor disability in childhood. People with CP may have varying degrees of activity limitation, which affect their cardiorespiratory and muscle fitness. The overall aim of the thesis was to study the health effects of Frame Running in individuals with CP and ambulatory difficulties (Gross Motor Function Classification System, GMFCS II-V). Frame Running is an exercise and parasport that enables moderate-to-high intensity physical activity in individuals with severely impaired posture, balance, and motor control. Therefore, study I investigated the effects of a Frame Running training intervention. Study II and IV explore whether the six-minute Frame Running test (6- MFRT) is a valid measure for cardiorespiratory fitness, i.e., maximal oxygen consumption (VO2peak). Finally, determinants (apart from VO2peak) of Frame Running capacity in athletes with CP were explored (study III). Methods Study I involved 15 participants with CP at GMFCS level I-IV, who completed 12 weeks of Frame Running training, with pre and post evaluation of cardiorespiratory endurance (6- MFRT), muscle thickness (ultrasound), and passive range of motion. Study II involved 24 participants with CP at GMFCS level II-IV, who performed the 6-MFRT with measure of cardiorespiratory parameters such as heart rate (HR), oxygen consumption (VO2peak) and respiratory exchange ratio (RER). Study III involved 62 participants with CP at GMFCS level I-V, who completed the 6-MFRT test as a measure of Frame Running capacity. Prior to 6-MFRT multiple specific lower limb impairments and muscle thickness was investigated. Study IV involved 16 participants with CP at GMFCS levels II-V, who performed the 6-MFRT and Frame Running Incremental Treadmill test (FRITT) to compare the cardiorespiratory response and blood lactate levels. Results In study I, Frame Running training improved cardiorespiratory endurance (6-MFRT) with 34%, and muscle thickness of the gastrocnemius in the most affected leg with 9%. There were strong correlations between 6-MFRT distance and VO2peak in both study II and IV, and >75% of the participants reached a (near) maximal exertion based on HR and RER-criteria. Moreover, a strong correlation between the VO2peak obtained during the 6-MFRT and FRITT was observed, with no significant differences in any cardiorespiratory parameters or blood lactate. A backward univariate linear regression analysis indicated that distance, sex, body weight, and height were significant predictors of VO2peak (L/min) during the 6-MFRT (Study IV). The orthogonal partial least square (OPLS) regression analysis revealed a modest degree of covariance in the variables analyzed, and that the variance in the 6-MFRT distance could be predicted with 75% accuracy based on >50 variables measured. Variable Importance in Projection (VIP) analysis indicated hip and knee extensor spasticity (negative effect), and muscle thickness (positive effect) arose as the most important factors contributing to Frame Running capacity (Study III). Conclusion Frame Running is a powerful and effective exercise modality in individuals with CP, promoting health-enhancing cardiorespiratory and peripheral adaptations. The Frame Runner can be used for aerobic exercise testing, where the 6-MFRT is valid and practical. Apart from aerobic capacity, spasticity around the hip and knee (negative effect) and muscle mass (positive effect) appears to be the most important factors contributing to Frame Running capacity. These findings are an important resource to enable optimization of training regimes to improve Frame Running capacity and contribute to evidence-based and fair classification for this parasport