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.

Access to abstract permanently restricted to Ball State community only. / Access to thesis permanently restricted to Ball State community only. / School of Physical Education, Sport, and Exercise Science

When O2 uptake at the lung is used to characterise the oxidative metabolic response to increased contractile activity ( O2 kinetics) in exercising muscle, the O2 profile reflects the combined influence of all involved muscle fibres. Consequently, during high-intensity exercise that mandates activation of fibres with considerable metabolic diversity (e.g., both principal fibre types), response characteristics specific to discrete segments of the recruited pool cannot be determined. The purpose of this thesis was to identify fibre-type-specific effects of conditions that might impact O2 delivery and/or motor unit recruitment patterns on O2 kinetics by using two models that increase fibre recruitment homogeneity during exercise transitions. In four experiments, subjects initiated high-intensity exercise from a moderate baseline (i.e., performed ‘work-to-work’ transitions; M→H) to target higher-order fibres, and in two experiments, subjects cycled at extremely slow and fast pedal rates to skew recruitment toward slow- and fast-twitch fibres, respectively. At mid-range contraction frequency, O2 kinetics (as indicated by the primary time constant, τp) was slower for M→H compared to unloaded-to-high-intensity transitions (U→H) (e.g., 42 v. 33 s; Ch 4) and this slowing was ~50% greater for M→H in a supine body position (decreased oxygenation; Ch 6). Slower kinetics was also present for U→H cycling at fast compared to slow pedal rates (τp, 48 v. 31 s; Ch 8). Conversely, M→H slowing relative to U→H was absent at extreme cadences (36 v. 31 s and 53 v. 48 s for slow and fast, respectively; Ch 7). After ‘priming’ (increased oxygenation), τp was reduced for U→H after fast-cadence priming only (Ch 8) and for M→H in the supine position (Ch 6), but unaffected for upright cycle and prone knee-extension M→H, for which priming reduced the O2 slow component and delayed-onset fibre activation (as indicated by iEMG; Chs 4 and 5). These results provide evidence in exercising humans that high-order fibres possess innately slow O2 kinetics and are acutely susceptible to interventions that might alter O2 delivery to muscle.

The purpose of this thesis is to extend understanding of the muscle metabolic responses of children and adolescents during exercise using the non-invasive technique of 31P-magnetic resonance spectroscopy (31P-MRS). The first experimental paper examined the reliability of measuring parameters of muscle metabolism in 11-12 year old children over three exhaustive incremental tests using a single-legged quadriceps ergometer. Exercise performance (peak power: ~ 10% coefficient of variation [CV]) and metabolic variables (muscle phosphate and pH intracellular thresholds [IT]: ~ 10% CV, and pH: ~ 1% CV at exhaustion) demonstrated good reliability, whereas the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) at exhaustion had poor reproducibility (~ 50% CV). The second paper examined the influence of age and sex on the muscle metabolic responses during incremental exercise in 9-12 year old children and young adults. The Pi/PCr and pH responses before and at the ITs were independent of age and sex, although during exercise above the ITs, the anaerobic energy contribution (increase in Pi/PCr, fall in pH) was higher in adults than children and in females compared with males, indicating an intensity dependence on age- and sex-related differences in muscle energetics. The third paper examined the relationship between the dynamics of muscle PCr, a putative controller of muscle respiration, and pulmonary oxygen uptake (pVO2) in 9-10 year old children during moderate intensity quadriceps and cycling exercise respectively. No differences were found between the PCr and phase II VO2 time constants at the onset (PCr 23 s [SD 5] vs. pVO2 23 s [SD 4]; P=1.000) or offset (PCr 28 s [SD 5] vs. pVO2 29 s [SD 5]; P=1.000) of exercise, suggesting an age-related slowing of the phosphate linked controller(s) of mitochondrial oxidative phosphorylation may underlie the faster pVO2 kinetics found in children compared to adults. The final experimental chapter tested this hypothesis, but no age or sex related differences were found in the PCr kinetic time constant at the onset (boys: 21 s [SD 4]; girls: 24 s [SD 5]; men: 26 s [SD 9]; women: 24 s [SD 7], P>0.200) or offset (boys: 26 s [SD 5]; girls: 29 s [SD 7]; men: 23 s [SD 9]; women: 29 s [SD 7], P>0.070) of exercise. In conclusion, this thesis has demonstrated that muscle metabolic parameters determined by 31P-MRS are suitable for the study of developmental exercise metabolism. During exercise below the metabolic ITs, the phosphate-linked regulation of muscle respiration is comparable between children and adults, although during exercise above the ITs children are characterised by a lower ‘anaerobic’ energy turnover than adults, indicating an age-related modulation of metabolic control during high intensity exercise.

The critical power (CP) model includes two constants: the CP and the W′ [P = W′ / t) + CP]. The W′ is the finite work capacity available above CP. Power output above CP results in depletion of the W′; complete depletion of the W′ results in exhaustion. It is possible to model the charge and discharge of the W′ during intermittent exercise using a novel integrating model (the W′BAL model), and to generate a function describing a curvilinear relationship between time constants of reconstitution of the W′ in terms of the difference between recovery power and CP (DCP) (r2 = 0.77). The depletion of the W′ as predicted by the W′BAL model during intermittent exercise is linearly related to the rise in V ̇O_2 above exercise baseline (r2 = 0.82 – 0.96). During intermittent exercise, the W′BAL model is generally robust with respect to the length of work and recovery interval, yielding a mean under-prediction of the W′BAL of only -1.6 ±1.1 kJ. The amount of W′ remaining after a period of intermittent exercise correlates with the difference between the subject’s V ̇O_2 at that time (V ̇O_2START) and V ̇O_2PEAK (DVO2) (r = 0.79, p < 0.01). Moreover, the W′BAL model also performs well in the field, permitting accurate estimation of the point at which an athlete becomes exhausted during hard training or competition (mean W′BAL at exhaustion = 0.5 ± 1.3 kJ (95% CI = 0 – 0.9 kJ). The W′BAL model meets the mathematical criteria of an excellent diagnostic test for exhaustion (area under ROC curve = 0.91). 31P magnetic resonance spectroscopy during single leg extensor exercise revealed a correlation between the recovery of the W′BAL model and recovery of creatine phosphate ([PCr]) after a bout of exhaustive single leg extensor exercise (r = 0.99, p < 0.01). The W′BAL model also accurately predicted recovery of the W′ in this setting (r = 0.97, p < 0.05). However, a complete understanding of the relationship between the depletion and recovery of [PCr] and the depletion and recovery of the W′ remains elusive. Muscle carnosine content is curvilinearly related to the rate of W′BAL recovery, with higher muscle carnosine associated with faster recovery, with implications for muscle buffering capacity and calcium handling. The W′BAL model may be recast in the form of a differential equation, permitting definition of the time constant of recovery of the W′BAL in terms of the subject’s known W′ and the DCP. This permits the scaling of the model to different muscle groups or exercise modalities. Moreover, modifications to this mathematical form may help explain some of the variability noted in the model in earlier studies, suggesting novel avenues of research. However, the present formulation of the W′BAL model is mathematically robust and represents an important addition to the scientific armamentarium, which may aid the understanding the physiology of human performance.

Orientador: Ellen Cristini de Freitas / Banca: Marcelo Papoti / Banca: Julio Sérgio Marchini / Resumo: A taurina é um aminoácido não essencial que atua principalmente no músculo esquelético evitando lesões musculares e auxiliando no tônus muscular. Visto a importância de um aporte nutricional adequado considerando calorias, carboidratos e proteínas, a fim de maximizar a recuperação após o treino e minimizar o risco de lesões musculares, a utilização de taurina seria uma alternativa para prevenir a inflamação e danos musculares, favorecer o processo de síntese proteica e reparo muscular e consequentemente melhorar a qualidade do treino sequencial dos triatletas. OBJETIVO: Analisar os efeitos de 8 semanas de suplementação de taurina e achocolatado sobre os marcadores de lesão muscular, resposta inflamatória e a capacidade aeróbia em triatletas. MÉTODOS: Foi realizado um estudo duplo cego, crossover, randomizado o qual contou com a participação de 9 triatletas da categoria de longa distância, do sexo masculino, com idade entre 25 a 35 anos. Foi realizada a suplementação de 3 gramas de taurina (TAU) ou placebo (PLA) associado a 400 ml de achocolatado de baixo de teor de gordura, durante o período de 8 semanas. Foram coletadas amostras de sangue antes (Pré) e após (Pós) cada período de suplementação para quantificação de marcadores de lesão muscular como lactato desidrogenase (LDH) e creatina quinase (CK), e também de marcadores inflamatórios como fatores de necrose tumoral-alfa (TNF-alfa) e interleucina-6 (IL-6). O desempenho físico dos triatletas foi avaliado por teste de exaustão em esteira. RESULTADOS: Foi constatado um aumento significativo nas concentrações de CK após a suplementação taurina (p=0,01). Entretanto as concentrações de LDH não apresentaram diferença significativa após as suplementações realizadas (TAU 16 Pré; 270,13±141,3 U.L-1 e... / Abstract: Taurine is an essential amino acid that acts primarily in skeletal muscle preventing muscle damage and improving muscle tone. Given the importance of an adequate nutritional supply considering calories, carbohydrates and proteins in order to maximize recovery after training and to minimize the risk of muscle damage, the use of taurine would be an alternative to prevent the inflammation and muscle damage, favor the process of protein synthesis and muscle repair and consequently improve the quality of triathlon training. In order to verify the effects of 8 weeks of taurine and chocolate milk supplementation, markers of muscle damage and inflammatory response, and aerobic capacity were quantified in triathletes. METHODS: A double-blind, crossover, randomized study was conducted with 9 male long distance triathletes, aged 25-35 years. Supplementation of 3 g of taurine was performed (TAU) or placebo (PLA) associated with 400 ml low fat chocolate milk during an 8-week period. Blood samples were collected before (Pre) and after (Post) each supplementation period for quantification of markers of muscle damage: Lactate dehydrogenase (LDH), creatine kinase (CK), inflammatory markers: tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), the physical performance of triathletes was evaluated by treadmill test until exhaustion. RESULTS: It was observed a significant increase in CK levels after TAU supplementation (p = 0.01). However, LDH concentrations did not differ significantly after the supplementations performed (TAU Pre; 270.13 ± 141.3 UL-1 and Post 350 ± 186 UL-1 ); (PLA Pre 196.07 ± 78.1 UL-1 and Post 230.2 ± 98.5 UL-1 ), and there were no changes in physical performance parameters; Anaerobic Threshold (TAU Pré 11,05±0,7 km/h e Pós 11,12±0,94 km/h); (PLA Pré 11,1±0,8 km/h e Pós 18 11,05±1,2), ... / Mestre

Priming exercise, or the ‘warm-up’, is an accepted practice prior to exercise participation, physical training or sporting competition. Traditionally, low intensity exercise has been used prior to both short- and long-duration events in an effort to prepare the athlete, but not fatigue them. Recently, however, a more scientific approach to priming exercise has been considered important, with some research suggesting that a high intensity intermittent priming strategy may be optimal. However, given the paucity of performance focussed ‘warm-up’ studies, and that existing data regarding high-intensity priming strategies is inconclusive, the aim of this thesis was to determine the effects of three high-intensity intermittent priming strategies on physiological responses and subsequent 3km laboratory time-trial (TT) performance. Ten well-conditioned endurance-trained male cyclists (mean ± SD: age, 28.3 ± 8.4 yr, body mass, 81.8 ± 11.6 kg, stature, 1.8 ± 0.1 m, O2peak, 4.6 ± 0.5 L•min−1) were recruited for this study. After an initial incremental exercise test to exhaustion, participants completed four 3km time trials (TT) on four separate occasions, each preceded by a different priming strategy. These included a ‘self-selected’ (control) condition, and three high-intensity intermittent priming strategies of varying intensity (100% and 150% of the power at O2peak, and all-out) and fixed duration (15 minutes), each in predetermined random order. Five minutes passive rest separated each priming exercise condition from the experimental 3km-TT. Oxygen uptake ( O2) and heart rate (HR) were measured continuously, while blood lactate concentration ([BLa]) and core temperature (TC) were recorded at rest, post-priming exercise, and immediately prior to and following the 3km-TT. In an attempt to provide a mechanistic explanation for changes in performance, O2 kinetic variables were determined from the O2 data. Performance was quantified as a mean power (Wmean) and total time taken to complete the 3km-TT. Mean power output and time taken for each 500m segment of the 3km-TT were also calculated. Results demonstrated that the athletes self-chosen priming condition (378.6 ± 44.0 W) resulted in Wmean that was slightly greater than both the lowest (376.3 ± 44.9 W; 0.7%; p = 0.57) and moderate (373.9 ± 47.8 W; 1.5%, p = 0.30) intensity intermittent priming condition, but significantly greater than the ‘all-out’ intermittent sprint priming condition (357.4 ± 44.5 W; 5.8%, p = 0.0033). Similar differences were observed for time. While differences existed in the O2 deficit (however, mainly non-significant), these differences did not provide clear explanations for the differences in performance, with the moderate priming condition displaying a significantly reduced O2 deficit (59.4 ± 15.6 L, p < 0.05), despite the non-significant change in Wmean, compared to the self-chosen priming condition (73.3 ± 18.6 L). Additionally no significant differences were observed in either the time constant or the mean response time of O2. Significant findings with regard to HR, [BLa] and TC were observed, but consistent with O2 kinetic variables, they were not related to, nor explain performance changes. In conclusion, regardless of intensity, different high-intensity intermittent priming exercise did not improve 3km-TT performance more than the control condition (self-chosen). A priming strategy that is overly intense was detrimental to subsequent cycling performance. The observed finding that a self-chosen priming strategy resulted in a comparable performance suggests that athletes are able to self-select (consciously or sub-consciously) a ‘warm-up’ that is of appropriate intensity/duration. Further work utilising the priming strategies from the current study with events of shorter duration is required to further clarify how priming strategies of this nature may affect track cycling performance.

PowerCranks(tm) are claimed to increase economy of motion and cycling efficiency by reducing the muscular recruitment patterns that contribute to the resistive forces occurring during the recovery phase of the pedal stroke. However, scientific research examining the efficacy of training with PowerCranks(tm) is lacking. Therefore, the purpose of this study was to determine if five weeks of training with PowerCranks(tm) improves economy of motion (EOM), gross efficiency (GE), oxygen uptake (V.O2) and muscle activation patterns in trained cyclists. Sixteen trained cyclists were matched and paired into either a PowerCranks(tm) (PC) or Normal Cranks (NC) training group. Prior to training, all subjects completed a graded exercise test (GXT) using normal bicycle cranks. Additionally, on a separate day the PC group performed a modified GXT using PowerCranks? and cycled only until the end of the 200W stage (PCT). During the GXT and PCT, FeO2, FeCO2 and V.E were measured to determine EOM, GE and V.O2max. Integrated electromyography (iEMG) was also used to examine selected muscular activation patterns. Subjects then repeated the tests following the completion of training on their assigned cranks.

The effective of additional muscle mass in a priming exercise on cardiac output (Q) and pulmonary oxygen uptake (VO2) kinetics (mean response time, s) were determined in cyclists. Outcomes were measured over four trials, each consisting of a 6-minute legs alone (UAL) or arms and legs (ULO) warm-up, 3 minute passive recovery, then 6 minutes leg cycling (PAL, PLO; respectively). Q was significantly higher preceding exercise onset with PAL compared to PLO or ULO (0.72 ± 0.13 vs. 0.58 ± 0.09, 0.43 ± 0.09 L∙min-1; respectively, P < 0.05). Q kinetics did not differ between unprimed (ULO: 38.9 ± 8.6) and primed exercise regardless of muscle mass (PLO: 38.6 ± 11.0; PAL: 40.7 ± 11.3). VO2 kinetics were faster (P < 0.05) with PAL (36.9 ± 6.0) compared to ULO (58.7 ± 10.5). Muscle mass employed during priming exercise had only slight effect on subsequent VO2 and Q responses.

The effective of additional muscle mass in a priming exercise on cardiac output (Q) and pulmonary oxygen uptake (VO2) kinetics (mean response time, s) were determined in cyclists. Outcomes were measured over four trials, each consisting of a 6-minute legs alone (UAL) or arms and legs (ULO) warm-up, 3 minute passive recovery, then 6 minutes leg cycling (PAL, PLO; respectively). Q was significantly higher preceding exercise onset with PAL compared to PLO or ULO (0.72 ± 0.13 vs. 0.58 ± 0.09, 0.43 ± 0.09 L∙min-1; respectively, P < 0.05). Q kinetics did not differ between unprimed (ULO: 38.9 ± 8.6) and primed exercise regardless of muscle mass (PLO: 38.6 ± 11.0; PAL: 40.7 ± 11.3). VO2 kinetics were faster (P < 0.05) with PAL (36.9 ± 6.0) compared to ULO (58.7 ± 10.5). Muscle mass employed during priming exercise had only slight effect on subsequent VO2 and Q responses.