Evaluation of the numeric rating scale for perception of effort during isometric elbow flexion exercise

This is the author's accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s00421-011-2074-1.The aim of the study was to examine the reliability and validity of the numerical rating scale (0-10 NRS) for rating perception of effort during isometric elbow flexion in healthy people. 33 individuals (32 ± 8 years) participated in the study. Three re-test measurements within one session and three weekly sessions were undertaken to determine the reliability of the scale. The sensitivity of the scale following 10 min isometric fatiguing exercise of the elbow flexors as well as the correlation of the effort with the electromyographic (EMG) activity of the flexor muscles were tested. Perception of effort was tested during isometric elbow flexion at 10, 30, 50, 70, 90, and 100% MVC. The 0-10 NRS demonstrated an excellent test–retest reliability [intra class correlation (ICC) = 0.99 between measurements taken within a session and 0.96 between 3 consecutive weekly sessions]. Exploratory curve fitting for the relationship between effort ratings and voluntary force, and underlying EMG showed that both are best described by power functions (y = ax b ). There were also strong correlations (range 0.89–0.95) between effort ratings and EMG recordings of all flexor muscles supporting the concurrent criterion validity of the measure. The 0-10 NRS was sensitive enough to detect changes in the perceived effort following fatigue and significantly increased at the level of voluntary contraction used in its assessment (p < 0.001). These findings suggest the 0-10 NRS is a valid and reliable scale for rating perception of effort in healthy individuals. Future research should seek to establish the validity of the 0-10 NRS in clinical settings.School of Health Science and Social Care, Brunel Universit

The Effect of Exercise Priming on V̇O2 Kinetics, Muscle Torque Complexity and Exercise Tolerance during Intermittent Isometric Contractions.

Exercise priming can alter V̇O2 kinetics and improve the performance of subsequent exhaustive heavy exercise. During fatiguing isometric exercise there is a reduction in the complexity of muscle torque output, which correlates with metabolic changes observed in the same exercise domain. This study aims to investigate the effect of exercise priming on V̇O2 kinetics, muscle torque complexity and exercise tolerance during intermittent isometric exercise. Five males and five females (25 ± 6 years, 171.4 ± 9.3 cm, 69.2 ± 12.0 kg) completed three experimental trials in a randomised order. The trials consisted of a six-minute priming exercise bout or rest period, followed by 20 minutes of rest, before completing a second exhaustive exercise bout. Participants performed intermittent isometric contractions of the knee extensors at 40% maximal voluntary contraction (MVC) with a duty cycle of 0.6. Participants' rate of perceived exertion (RPE) and muscle oxygen consumption were measured at regular intervals throughout the exercise. There was no difference in the time to task failure between primed and non-primed exercise. There was a higher EMG amplitude at the start of the primed exhaustive bout compared to the non-primed exercise bout. The V̇O2 response to exhaustive exercise was not different between the primed and non-primed conditions. Peripheral fatigue was present at the onset of exercise following priming and a significant loss of muscle torque complexity with priming. There was no improvement in performance of subsequent intermittent isometric contractions with prior exercise, nor was there change in the V̇O2 response. Loss of complexity could be attributed to the increase in arEMG at the onset of the exhaustive exercise, more specifically an increase in motor unit recruitment with the development of fatigue. These results suggest that there is some effect of high-intensity prior exercise on exhaustive isometric contractions of the knee extensors

Investigating the physiological mechanisms of the oxygen consumption \u201cslow component\u201d.

The study of the oxygen consumption (VO2) kinetics is focused on the understanding of how human metabolism adjusts during the transition from a condition of resting/movement to another in order to satisfy the new energetic demand. As an integrated index of pulmonary, cardiovascular and muscles capacity VO2 kinetics have gained progressively increasing interests during the XX and the early XXI centuries. Thanks to the development of new technologies as well as an always increasing community of interested scientists in this subject, the knowledge in this field has been expanded considerably. However, some of the topics related to VO2 kinetics remain debated and call for further research. One of these topics is the loss of efficiency of human locomotion that occurs at the higher metabolic intensities, after the transitory period in which a new steady-state in VO2 should be achieved. This phenomenon is typically called VO2 \u201cslow component\u201d, as representative of a further increase in VO2 after the expected steady-state. The importance of the VO2 slow component lies in its link with exercise tolerance and on the understanding of the adaptations of the human body during physical activity. Therefore, researchers have tried to define the physiological underpinning of the slow component and to develop intervention strategies to reduce its amplitude. Nevertheless, a number of physiological uncertainties regarding the mechanistic bases of the slow component exist and require to be clarified. The purpose of this thesis was to deal with this gap and to study the origins of the VO2 slow component, and the loss of efficiency of locomotion that the slow component represents. In chapter one, a brief explanation of the VO2 response during exercise and the current explanatory theories for the VO2 slow component are provided. In chapter two, the experimental aims of the thesis are explained. Then, the results of four different studies are presented in chapters three, four, five, and six. Finally, chapter seven summarizes the main findings of this research work

EFFECTS OF DIFFERENT PEDALING POSITIONS BY DYNAMIC-FITTING ON MUSCLE FATIGUE AND ENERGY EXPENDITURE IN AMATEUR CYCLISTS

Inappropriate cycling positions may affect muscle usage and raise the fatigue level or risk of sport injury. Dynamic bike fitting helps the cyclists select proper bikes and adjust them to fit their ergometry. The purpose of this study is to investigate how different “knee forward of foot” (KFOF) distances can influence the rate of muscle fatigue and the energy expenditure during long periods of cycling. 6 amateur cyclists were recruited to perform the graded exercise testing with different pedaling positions at four KFOF distances (+20, 0, -20, and -40 mm). Our results revealed that the muscle fatigue level, oxygen consumption and respiratory exchange that were evaluated by the Surface EMG and portable energy metabolism system would be significantly increased with KFOF at 20 and -40 mm when compared to those with KFOF at 0 and -20 mm

The reliability of 10 km treadmill time trial performance and the effect of different high intensity interval training strategies on 10 km running performance and associated physiological parameters

The reliability and validity of a performance test is important in research to detect meaningful performance differences following an intervention. In accordance with this, the aim of the first study of this thesis was to investigate the reliability and validity of a self-paced 10 km treadmill time trial. This performance measure was then used in the main section of this thesis. This comprised a large training intervention study aimed to answer specific questions following three different high intensity interval training programmes. In particular, changes in 10 km running performance were investigated with respect to various physiological parameters, both immediately following the training intervention, as well as during a subsequent three-week taper period. Methods In the first study, a group of well-trained male runners (n = 8) completed four 10 km treadmill time trials and two 10 km track time trials. Comparisons in performance time were made between the 10 km treadmill time trials to determine the typical percent error between these trials. Additionally, comparisons were made between the track and treadmill time trials. In the second study, well-trained male runners(n = 32) were randomly assigned to one of four groups; a control group, a 400 m interval group, a 1600 m interval group and a mixed (400 m and 1600 m) interval group. The intensity of the intervals was based on the participants' current 10 km time trial time. The high intensity training interventions consisted of eight interval sessions (twice per week) over a four-week period followed by a three-week singlestep30% reduction in total training volume (while maintaining training frequency and some intensity) in all groups

Mechanical Efficiency Is Lower After Cycling Compared To After Running In Trained Triathletes

Triathlon involves swimming, cycling, and running. PURPOSE: To examine whether a 40-km cycling bout alters running economy (RE) and mechanical efficiency of running (ME) in trained triathletes. METHODS: Eight competitive triathletes (7 M, 1 F; 21.0±1.5 yrs; VO2max 59.2±7.6 mL?kg-1?min-1) with a minimum of one-year experience competing in triathlons. Subjects reported to the lab for 3 separate visits. At visit 1, subjects completed the informed consent, a VO2max test, anthropometric measures, and baseline performance testing [isometric squat (MVC) and countermovement jump (CMJ)]. During the 2nd visit, RE and ME were measured after subjects completed a 5-km treadmill run (R5K). For visit 3, RE and ME were measured after subjects completed 40-km of cycling (C40K). MVC, CMJ, and muscle glycogen values were measured before and after the exercise bout on visits 2 and 3. RESULTS: ME after C40K was significantly lower than ME after R5K (C40K: 48.4±5.7%, R5K: 53.7±3.5%; p=0.004). RE, blood lactate, respiratory exchange ratio, work, glycogen, CMJ, or MVC were not statistically different between C40K and R5K. CONCLUSION: The lower ME in running observed following cycling might be due to the combined effect of slightly higher blood lactate and RER values, and slightly lower external mechanical work performed

Tecniche e metodi per un'analisi multiscala del fenomeno della fatica muscolare

This thesis proposes an integrated holistic approach to the study of neuromuscular fatigue in order to encompass all the causes and all the consequences underlying the phenomenon. Starting from the metabolic processes occurring at the cellular level, the reader is guided toward the physiological changes at the motorneuron and motor unit level and from this to the more general biomechanical alterations. In Chapter 1 a list of the various definitions for fatigue spanning several contexts has been reported. In Chapter 2, the electrophysiological changes in terms of motor unit behavior and descending neural drive to the muscle have been studied extensively as well as the biomechanical adaptations induced. In Chapter 3 a study based on the observation of temporal features extracted from sEMG signals has been reported leading to the need of a more robust and reliable indicator during fatiguing tasks. Therefore, in Chapter 4, a novel bi-dimensional parameter is proposed. The study on sEMG-based indicators opened a scenario also on neurophysiological mechanisms underlying fatigue. For this purpose, in Chapter 5, a protocol designed for the analysis of motor unit-related parameters during prolonged fatiguing contractions is presented. In particular, two methodologies have been applied to multichannel sEMG recordings of isometric contractions of the Tibialis Anterior muscle: the state-of-the-art technique for sEMG decomposition and a coherence analysis on MU spike trains. The importance of a multi-scale approach has been finally highlighted in the context of the evaluation of cycling performance, where fatigue is one of the limiting factors. In particular, the last chapter of this thesis can be considered as a paradigm: physiological, metabolic, environmental, psychological and biomechanical factors influence the performance of a cyclist and only when all of these are kept together in a novel integrative way it is possible to derive a clear model and make correct assessments