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On the Importance of Testing Time Delay to Assess Central Fatigue Induced by Endurance Exercise
Medicine and Science in Sports and Exercise, 2014
The purposes of the present study were twofold: 1) to determine if the model used for estimating the physical working capacity at the fatigue threshold (PWC FT) during incremental cycle ergometry could be applied to treadmill running to derive a new neuromuscular fatigue threshold, and 2) to compare the running velocities associated with the PWC FT , ventilatory threshold (VT), and respiratory compensation point (RCP). METHODS: Fifteen moderately-trained males and females (mean age ± SD = 21.5 ± 1.3 yrs; 68.7 ± 10.5 kg; 175.9 ± 6.7 cm) volunteered to perform an incremental treadmill test that began at 6.0 mph (1% grade) and increased 1.0 mph every two minutes until volitional fatigue. Expired gas samples were collected for the determination of VT and RCP. During each 2min stage of the test, six, 10-second electromyographic (EMG) samples were recorded from the vastus lateralis. The EMG amplitude (µVrms) values were calculated for each 10-second epoch and separately plotted across time for each stage (i.e. running velocity) of the test. The PWC FT was then determined by averaging the highest running velocity that resulted in a non-significant (P > 0.05) slope coefficient for the EMG amplitude versus time relationship, with the lowest running velocity that resulted in a significant (P < 0.05) positive slope coefficient. RESULTS: The one-way ANOVA with repeated-measures and post-hoc analyses indicated there were significant mean differences in running velocities between the VT (7.0 ± 0.8 mph) and PWC FT (8.7 ± 1.4 mph), and the VT and RCP (8.7 ± 1.1 mph), but not between the PWC FT and RCP. In addition, there were significant zero-order correlations for VT versus PWC FT (r = 0.70), RCP versus PWC FT (r = 0.70), and VT versus RCP (r = 0.91). CONCLUSIONS: The findings of the present study indicated that the PWC FT model used to estimate the onset of neuromuscular fatigue during cycle ergometry could be applied to incremental treadmill running. Theoretically, the PWC FT treadmill test estimates the maximal running velocity that can be sustained for an extended period of time without fatigueinduced increases in muscle activation. The present findings also indicated that the PWC FT and RCP occurred at the same exercise intensity (i.e. running velocity) and thus, may be related to a common physiological mechanism of fatigue.
Frontiers in Physiology
Purpose: The aim of this study was to investigate the interaction of training load quantification using heart rate (HR) and rating of perceived exertion (RPE)-based methodology, and the relationship between internal training load parameters and subjective training status (Fatigue) in high-level rowers during volume increased low-intensity training period.Methods: Training data from 19 high-level rowers (age 23.5 ± 5.9 years; maximal oxygen uptake 58.9 ± 5.8 ml·min−1·kg−1) were collected during a 4-week volume increased training period. All individual training sessions were analyzed to quantify training intensity distribution based on the HR time-in-zone method (i.e., HR Z1, HR Z2, and HR Z3) determined by the first and second ventilatory thresholds (VT1/VT2). Internal training load was calculated using session RPE (sRPE) to categorize training load by effort (i.e., sRPE1, sRPE2, and sRPE3). The Recovery-Stress Questionnaire for Athletes (RESTQ-Sport) questionnaire was implemented af...
Quantitative and non-invasive measurement of exercise-induced fatigue
Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology, 2018
Prolonged exercise-induced muscular fatigue adversely affects physical performance. The fatigue increases the risk of sport injuries, whereas early fatigue detection and assessment can prevent injuries. An assessment of the most crucial impacts of fatigue on physical performance leads to the development of an accurate, non-invasive and objective muscular fatigue measurement method. The most common manifestation of exercise-induced fatigue is a significant decline in force produced by the muscles that in turn affects motion characteristics. This directly alters body postural behaviour and decreases the amount of kinetic energy produced by the subject. The current non-invasive and objective methods to measure fatigue and analyse motion characteristics cannot provide a comprehensive information about muscular fatigue because of their limited ability to record different aspects of motion. An objective and non-invasive assessment method of exercise-induced fatigue, in which the variation...
British Journal of Sports Medicine, 2011
Objective This study analysed cardiopulmonary, metabolic and rating of perceived exertion (RPE) responses during exercise bouts performed below, at and above the second lactate threshold (LT2) intensity. Methods 10 healthy men performed constant workloads to exhaustion at the fi rst lactate threshold (LT1), LT2 and 25% of the difference between LT2 and maximal aerobic power output (TW 25% ) identifi ed during an incremental test. The time to exhaustion (TE) was 93.8 (18.0), 44.5 (16.0) and 22.8 (10.6) min at LT1, LT2 and TW 25% , respectively (p < 0.001). Metabolic and cardiopulmonary parameters and RPE data were time normalised to the exercise bout duration. The correlation between the slope of these variables and TE was calculated. Results Differences were found for respiratory exchange ratio (RER), RPE and potassium at LT1; RER, RPE, norepinephrine and potassium at LT2; and ventilation, respiratory rate (RR), RPE, lactate and potassium at TW 25% . Except for RR, no cardiopulmonary or metabolic parameter increased signifi cantly after 50% of the exercise duration, indicating a physiological steady state. VO 2 , heart rate and lactate at exhaustion in all exercise bouts were signifi cantly lower than values reached in the maximal incremental test. The slope of most metabolic variables was not correlated to TE in LT1, LT2 and TW 25% , whereas the slope of RPE was signifi cantly correlated to TE (r = −0.72 to −0.84; p < 0.05) for the three exercise intensities. Conclusion Contrary to traditional suggestions, exercise at LT1, LT2 and TW 25% intensities is performed and terminated in the presence of an overall physiological steady state.
International Journal of Computer and Electrical Engineering, 2015
In this study, determination of fatigue at the onset, and following maximal loaded exercise was evaluated from mechanomyography (MMG) and electromyography (EMG) recordings in exercise trained men. Twenty four recreationally active men were participated into this study. Participants were performed a fatiguing Bruce Protocol which is widely-used maximal loading treadmill test. EMG and MMG recordings were obtained from rectus femoris muscle during maximal isometric contractions both at the onset, and following Bruce Protocol. Following pre-training measurements, volunteers were subjected to sprint running exercise involved 3 sessions per week for 8 weeks. MMG and EMG recordings were repeated following 8 weeks of sprint running training. Recordings were decomposed in 8 levels by using the wavelet packet transform and so windows with 15 nodes and 5 sliding nodes were created. Then the mean energy values at each window were obtained from the 24 persons group and were applied to the input of Multilayer Perceptron Neural Network (MLPNN). In the output, the classification process was performed both before and after fatiguing exercise, and the success rate of the test was evaluated for fatigue. In the post-training measurements, MMG has been failed to determine fatigue with decreased success rate, whereas EMG results were shown that success rate is increased by 20 percent compared to pre-training measurements.
Measuring and Evaluating Human Energy-Generating Capacities During Exercise
• Compare and contrast the concepts of measurement, evaluation, and prediction. • Explain specificity and generality applied to exercise performance and physiologic function. • Describe procedures to administer two practical "field tests" to evaluate power output capacity of the intramuscular high-energy phosphates (immediate energy system). • Describe a commonly used test to evaluate the power output capacity of glycolysis (short-term energy system). • Explain the differences between direct and indirect calorimetry. • Explain the differences between open-and closed-circuit spirometry. • Describe different measurement systems used in open-circuit spirometry. • Define the term respiratory quotient (RQ), including its use and importance. • Explain factors that influence RQ and respiratory exchange ratio. • Define maximal oxygen uptake (V. O 2max), including its physiological significance. • Define graded exercise stress test. • List criteria that indicate when a person reaches "true" V. O 2max and V. O 2peak during a graded exercise test. • Outline three commonly used treadmill protocols to assess V. O 2max. • Explain how each of the following affects V. O 2max : (1) mode of exercise, (2) heredity, (3) state of training, (4) gender, (5) body composition, and (6) age. • Describe procedures to administer a submaximal walking "field test" to predict V. O 2max. • Outline the procedure to administer a step test to predict V. O 2max. • List three assumptions when predicting V. O 2max from submaximal exercise heart rate.
Effect of Muscle Fatigue on EMG Signal and Maximum Heart Rate for Pre and Post Physical Activity
Journal of Electronics, Electromedical Engineering, and Medical Informatics
Sport is a physical activity that can optimize body development through muscle movement. Physical activity without rest with strong and prolonged muscle contractions results in muscle fatigue. Muscle fatigue that occurs causes a decrease in the work efficiency of muscles. Electrocardiography (ECG) is a recording of the heart's electrical activity on the body's surface. EMG is a technique for measuring electrical activity in muscles. This study aims to detect the effect of muscle fatigue on cardiac signals by monitoring ECG and EMG signals. This research method uses the Maximum Heart Rate with a research design of one group pre-test-post-test. The independent variable is the ECG signal when doing plank activities, while the dependent variable is the result of monitoring the ECG signal. To get the Maximum Heart Rate results, respondents use the Karnoven formula and perform the T-test. Test results show a significant value (pValue <0.05) in pre-exercise and post-exercise. Wh...
Prediction of Maximal or Peak Oxygen Uptake from Ratings of Perceived Exertion
Sports Medicine, 2014
Maximal or peak oxygen uptake ( _ VO 2 max and _ VO 2 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 _ VO 2 max or _ VO 2 peak. Because of the strong link between ratings of perceived exertion (RPE) and oxygen uptake ( _ VO 2 ), it has been proposed that the individual relationship between RPE and _ VO 2 (RPE: _ VO 2 ) can be used to predict _ VO 2 max (or _ VO 2 peak) from data measured during submaximal exercise tests. To predict _ VO 2 max or _ VO 2 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 _ VO 2 max or _ VO 2 peak from RPE: _ VO 2 measured during both GXT and PRET has received growing interest. A number of studies have tested the validity, reliability and sensitivity of predicted _ VO 2 max or _ VO 2 peak from RPE: _ VO 2 extrapolated to the theoretical _ VO 2 max at RPE 20 (or RPE 19 ). 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: _ VO 2 range used to plot the linear regression (e.g. RPE 9-13 versus RPE 9-15 versus RPE 9-17 during PRET), as well as the perceptual endpoint used for the extrapolation (i.e. RPE 19 and RPE 20 ). The _ VO 2 max or _ VO 2 peak predictions from RPE: _ VO 2 are also compared with heart raterelated predictive methods. This review suggests that _ VO 2 max (or _ VO 2 peak) may be predicted from RPE: _ VO 2 extrapolated to the theoretical _ VO 2 max (or _ VO 2 peak) at RPE 20 (or RPE 19 ). However, it is generally preferable to (1) extrapolate RPE: _ VO 2 to RPE 19 (rather than RPE 20 ); (2) use wider RPE ranges (e.g. RPE B 17 or RPE 9-17 ) in order to increase the accuracy of the predictions; and (3) use RPE B 15 or RPE 9-15 in order to reduce the risk of cardiovascular complications in clinical populations.
PloS one, 2015
Our study aimed to investigate changes of different markers for routine assessment of fatigue and recovery in response to high-intensity interval training (HIIT). 22 well-trained male and female team sport athletes (age, 23.0 ± 2.7 years; V̇O2max, 57.6 ± 8.6 mL·min·kg-1) participated in a six-day running-based HIIT-microcycle with a total of eleven HIIT sessions. Repeated sprint ability (RSA; criterion measure of fatigue and recovery), countermovement jump (CMJ) height, jump efficiency in a multiple rebound jump test (MRJ), 20-m sprint performance, muscle contractile properties, serum concentrations of creatinkinase (CK), c-reactive protein (CRP) and urea as well as perceived muscle soreness (DOMS) were measured pre and post the training program as well as after 72 h of recovery. Following the microcycle significant changes (p < 0.05) in RSA as well as in CMJ and MRJ performance could be observed, showing a decline (%Δ ± 90% confidence limits, ES = effect size; RSA: -3.8 ± 1.0, E...
Scandinavian Journal of Medicine and Science in Sports, 2000
A popular concept in the exercise sciences holds that fatigue develops during exercise of moderate to high intensity, when the capacity of the cardiorespiratory system to provide oxygen to the exercising muscles falls behind their demand inducing ''anaerobic'' metabolism. But this cardiovascular/anaerobic model is unsatisfactory because (i) a more rigorous analysis indicates that the first organ to be affected by anaerobiosis during maximal exercise would likely be the heart, not the skeletal muscles. This probability was fully appreciated by the pioneering exercise physiologists, A. V. Hill, A. Bock and D. B. Dill, but has been systematically ignored by modern exercise physiologists; (ii) no study has yet definitely established the presence of either anaerobiosis, hypoxia or ischaemia in skeletal muscle during maximal exercise; (iii) the model is unable to explain why exercise terminates in a variety of conditions including prolonged exercise, exercise in the heat and at altitude, and in those with chronic diseases of the heart and lungs, without any evidence for skeletal muscle anaerobiosis, hypoxia or ischaemia, and before