The Borg 6–20 rating of perceived exertion (RPE) scale is a common measure reported during exercise testing and training, and is usually taken as a response measurement to provide a subjective assessment of exercise intensity. A lesser used application of the scale is for regulating exercise intensity, referred to as its ‘production mode’. Recent research on this topic initiated by Eston et al. (2005) has led to a novel application of this procedure as a means of predicting an individual’s maximal oxygen uptake ( O2max) via a perceptually-regulated exercise test (PRET). The PRET could play a significant role in guiding exercise prescription and monitoring cardiorespiratory fitness levels in situations where the normal heart rate response is affected. The aim of this thesis is to develop further and test the integrity of the PRET technique. Firstly, a review of the evidence on the validity and reliability of the Borg RPE scale when used to regulate exercise intensity in healthy and unhealthy adults is presented, as to-date, no scholarly publication has synthesised the body of knowledge on this specific application of the scale. Subsequently, four studies were completed to investigate the effects of different methodological variations on the predictive capabilities of the PRET, including an examination (for the first time) of its utility among heart failure patients (Study 4). Study 1 re-visited the validity and reliability of the PRET technique utilising a modified protocol of differing durations (2 and 4 min bouts), with revised instructions and placing the graded exercise test (GXT) as the final trial during cycle ergometry. Superior results were observed to those reported in previous investigations (Eston et al., 2008; Faulkner et al. 2007; Eston et al., 2006) during the 3 min trial, further reinforcing the validity and reliability of this technique. Accordingly, Study 2 was the first to investigate the reliability and validity of a treadmill PRET protocol with a ceiling intensity of RPE 15, rather than RPE 17, and observed that a safer modified PRET (with practice) provides acceptably valid and reliable predictions of O2max in healthy adults. In addition, Study 3 extended the research thus far by investigating the PRET protocol during cycle exercise, once again with a ceiling intensity of RPE 15, and demonstrated that (with practice) a cycle-based PRET can yield reliable and valid predictions of O2max that compare favourably to previous investigations. Finally, given that the research employing a PRET has unanimously alluded to its likely value in clinical populations among whom heart rate as a physiological response to exercise is affected (e.g. via medication) and precluded as a means predicting O2max, Study 4 investigated the utility of a PRET in a beta-blocked population of heart failure patients. In the event, it was observed that a PRET (up to RPE 15) was too strenuous and needs to be capped at an intensity of RPE 13 in this population. In addition a continuous protocol seemed unsuitable due to its length and it was recommended that a discontinuous PRET protocol be investigated. Future research needs to investigate the utilisation of the PRET (i) in different exercise modes; (ii) determine the optimum number of practice trials required; (iii) whether a discontinuous or continuous protocol is more appropariate; (iv) whether the extrapolation should be made to RPE 19 or 20 and; (v) whether the PRET can be employed succesfully in other clinical populations.

Sprint kayaking is prominent in Europe with training methods devised and adopted from Eastern bloc training systems. There is a lack of published research on sprint kayaking locally and internationally. Consequently, the aims of this research directly address establishing a relationship between kayak specific training and the Profile of Mood States (POMS); monitoring training duration and intensity and establish a link with the POMS and Rating of Perceived Exertion (RPE); to monitor the general wellness of the kayakers. Seven elite sprint kayakers (two male, five female) with the following characteristics: age 26.5 (1.4) years, training experience 8.4 (3.7) years were part of the South African national sprint kayaking squad selected to participate in this study, based on their preparation for the 2008 Beijing Olympic Games (one male athlete did not qualify but continued to train). The females trained for the 500m K1, K2 and K4 events and the male for the 1000m K1. Three training camps (TC1, TC2, TC3) were held from 12 November to 09 December 2007, 25 February to 22 March 2008 and 14 July to 04 August 2008. RPE (Borg Scale) was recorded for each session. The 65-item POMS was completed twice a week, after half a days rest (Wednesday) and after a day and half rest (Sunday). Daily training load was calculated from RPE and session time; and an energy index calculated from the POMS vigour and fatigue scores. The Wisconsin Upper Respiratory Symptom Survey recorded illness and injury. Descriptive and Inferential Statistics, Friedman’s rank test for k correlated samples, The Wilcoxon Signed Ranks Test, Spearman rank-order correlations were used to analyse the data. Statistical significance was calculated at 5% (p=0.05) and 10% (p=0.1). The results showed higher vigour scores associated with lower RPE and low training load; and high RPE associated with higher anger, confusion, depression, fatigue and total mood disturbance scores. There was a relationship between increasing POMS scores and duration of the training camps. The POMS findings could not completely explain the relationship found between RPE and duration of the training camps. The energy index was higher pre-camp and the extended rest periods during the camps. The findings for the POMS and RPE suggested that a state of overreaching might have occurred during the camps. Monitoring of the kayakers for an extended period after the training camps would have been useful to determine whether any of these individuals became over-trained. In accordance with Kentta et al (2006), regular use of the POMS may help detect under recovery, preventing staleness and unwanted rest for extended periods. Future studies will enable a retrospective view on these results. / Dissertation (MA)--University of Pretoria, 2012. / Biokinetics, Sport and Leisure Sciences / unrestricted

This study is a subset of a larger body of research that examined shoulder time to fatigue during overhead work in an attempt to reduce the prevalence and impact of work-related musculoskeletal problems in the shoulder associated with overhead work, particularly during automobile assembly. Existing evidence suggests that shoulder injuries are diverse in terms of tissues affected and symptoms presented. Furthermore, the cause of these injuries is multifactorial. The work presented here assumes that musculoskeletal injuries of the shoulder mechanism are at least related to, if not caused by, fatigue localized to the shoulder musculature. While the exact relationship between fatigue and injury has not been clearly established, there is consensus among researchers that fatigue plays and important role. Muscular fatigue, therefore, is viewed as a surrogate measure of risk, and task design to avoid fatigue is seen as a rational method to minimize this risk. An experiment to determine the effects of tool weight on shoulder fatigue and performance during overhead work with work/rest cycles was performed. Times to fatigue were derived based on dependent measures including total task duration, controlled maximum muscle contractions, subjective ratings based on Borg's CR-10 RPE scale, electromyogram behavior (MdPF), and hand force performance measures. Experimental findings indicated that duty cycle (percentage of total task cycle time spent working) significantly affected task duration (p<0.0001), changes in maximum voluntary contraction values for the infraspinatus (p<0.05), and the minimum time for any shoulder muscle to fatigue as determined by changes in the EMG power spectrum (p<0.05). Time to fatigue for the mid deltoid as determined by changes in the median frequency of the EMG power spectrum was shown to change significantly (p<0.05) with change in tool weight. Large intersubject variation was observed for the dependent measures, which showed subjects experiencing different levels of fatigue while performing the same task. Limitations of the study and recommendations for future direction are also discussed. / Master of Science

This thesis describes a series of experiments to investigate sex differences in neuromuscular fatigue mechanisms of the ankle muscles and related postural control changes in healthy young adults. We found that isometric exercise-induced ankle muscle fatigue led not only to significant declines in twitch contractile function and voluntary activation (using twitch interpolation technique, Article 2) but also to significant changes in the center of pressure (COP) sway (backward/right shifts of the COP position and/or increased COP sway velocity) during quiet standing and/or standing forward leaning (FL) task with eyes open and/or eyes closed (Articles 3 and 4). However, we found minor or no significant sex differences in the fatigue mechanisms and fatigue-induced COP sway changes regardless of task difficulty, except for a significant sex X fatigue interaction for COP sway velocity (Article 3). The interaction effect was due to a significant increase in sway velocity in males during the FL task with eyes closed (but not in females), suggesting that males may preferentially rely on ankle control during a relatively challenging task (as compared to females). The general lack of sex differences is not surprising given similar performance and/or perceived fatigability between the sex groups (Articles 2-4), which could be explained by the relatively small differences in contractile function (and/or muscle strength) between males and females for ankle plantar and dorsi flexors compared with other muscle groups. In addition, this thesis involves a scoping review (Article 1), which summarized the broad range of rating of perceived exertion (RPE) values documented in studies observing an effect of muscle fatigue on postural control and suggested the potential effect of various fatigue levels on postural changes. Collectively, these findings advance our understanding of sex-specific fatigue mechanisms and postural control behavior. These findings also indirectly contribute to the understanding of sex differences in injury risks during physically or stability-demanding tasks and sports, as well as to the improvement in the prescription of physical training or rehabilitation exercise.