▼ 

The aim of the study was to investigate the relationship of stroke rate and pacing in physiological and kinetic parameters during 2 km rowing ergometer. In the first part of the study, 36 male (15.09±0.7 yrs) and 12 female (14.9±0.5 yrs) rowers participated in the study. Both sexes were asked to row 2 km on the Concept 2 Model D rowing ergometer at the best possible time. For the statistical analysis Anova repeated measures were used and Pearson’s product. The results showed that male rowers decreased the SL in higher stroke rate(r= -0.6, p=0.001). Strong relationship for both genders was found between SL and height and upper and lower extremities. Kinetic variables changed every 500m. Both sexes, rowed the 2km using the parabolic-shaped pacing strategy. In the second part, 15 male rowers aged 15.37± 1.34 yrs, height 175.96±6.34 cm, body mass 72.84±10.13 kg completed 3 different pacing strategies in Concept II rowing ergometer. The purpose of the study was to investigate the influence of different pacing strategies on performance and selected metabolic and kinetic parameters. Participants first performed in Concept 2 an incremental test to determine VO2peak (59.97±4.86 ml•kg-1•min-1). After a week, performed a baseline 2km ergometer rowing trial. From the baseline data (BPS), pacing strategies were developed for the first 1000m. A slow pacing strategy (SPS) 4% slower from mean velocity of BSP and an even pacing strategy (EPS) were developed. The results showed best performance time in BPS. Kinetic characteristics were found to be consisted over BPS, SPS and EPS with the exception of stroke length which was greater in SPS. No differences were found in La (mmol.l-1) in recovery between pacing strategies (p=0.308) No significant differences were found in metabolic parameters. In conclusion, stroke rate has a strong relationship with stroke length (SL) and the kinetic characteristics of male and female rowers change every 500m of the race. In addition, male and female performance is different. BPS allowed rowers to cover the 2 km distance in higher stroke rate and in shorter performance time compared to SPS and EPS pacing strategies presenting same physiological responses.

Η παρούσα έρευνα σχεδιάστηκε για να εξετάσει τη σχέση του κωπηλατικού ρυθμού με τα κινητικά χαρακτηριστικά νεαρών κωπηλατών και κωπηλατριών καθώς και την επίδραση της απόστασης κωπηλάτησης και των διαφορετικών αγωνιστικών τακτικών στην απόδοση.Στην πρώτη εργασία, το δείγμα αποτέλεσαν 36 αγόρια (15.09±0.7 έτη) και 12 κορίτσια (14.9±0.5 έτη) αγωνιστικού επιπέδου. Τους ζητήθηκε να κωπηλατήσουν σε εργόμετρο Concept2 την αγωνιστική απόσταση των 2km με σκοπό να πραγματοποιήσουν τον καλύτερο δυνατό χρόνο τους. Η στατιστική ανάλυση έγινε με ανάλυση διασποράς (Anova) για επαναλαμβανόμενες μετρήσεις και Pearson’s product. Τα αποτελέσματα έδειξαν ότι το μήκος της κουπιάς (SL) στα αγόρια μειώνεται με την αύξηση του ρυθμού (r= -0.6, p=0.001). Αντίθετα, στα κορίτσια το SL δε συσχετίζεται με το ρυθμό. Το SL συσχετίζεται με το ανάστημα και το μήκος των άνω και…

▼ In this thesis a problem of determining the optimal pacing strategy to minimize travel time is considered. The problem is restricted to a straight race track with constant slope and rolling resistance, and no headwind. It is expressed as an optimal control problem that can be solved using Pontryagin's Maximum Principle. The control variable is the cyclist's power, which is modelled according to a hyperbolic power-time relationship, where a maximum power level is assumed. The Hamiltonian is linear with respect to this control variable. The minimum time problem is redefined as a maximum excursion problem, which is related to Goddard’s problem of a rocket's ascent through the atmosphere. It turns out that the optimal pacing problem is a singular control problem. Such problems are difficult to solve, both numerically and analytically, and they only occur sporadically in control theory. It is proven that the singular control only accurs during a single interval; optimal pacing starts with maximum power and decays through a singular control to minimum power. The singular arc may be degenerate; a bang-bang control might be optimal, depending on the length of the race track and the amount of available energy. The solution of the pacing problem has been obtained partly numerical and partly analytical. It applies to a straight course without bends, but it can be extended to an arbitrary course by dividing it into straight segments between bends and optimize over all distributions of energy over the segments. Advisors/Committee Members: Dajani, K., Fokkink, R., Olsder, G.J., Frank, J.E..

▼ 

In this thesis a problem of determining the optimal pacing strategy to minimize travel time is considered. The problem is restricted to a straight race track with constant slope and rolling resistance, and no headwind. It is expressed as an optimal control problem that can be solved using Pontryagin's Maximum Principle. The control variable is the cyclist's power, which is modelled according to a hyperbolic power-time relationship, where a maximum power level is assumed. The Hamiltonian is linear with respect to this control variable. The minimum time problem is redefined as a maximum excursion problem, which is related to Goddard’s problem of a rocket's ascent through the atmosphere. It turns out that the optimal pacing problem is a singular control problem. Such problems are difficult to solve, both numerically and analytically, and they only occur sporadically in control theory. It is proven that the singular control only accurs during a single interval; optimal pacing starts with maximum power and decays through a singular control to minimum power. The singular arc may be degenerate; a bang-bang control might be optimal, depending on the length of the race track and the amount of available energy. The solution of the pacing problem has been obtained partly numerical and partly analytical. It applies to a straight course without bends, but it can be extended to an arbitrary course by dividing it into straight segments between bends and optimize over all distributions of energy over the segments.

Applied mathematics

Electrical Engineering, Mathematics and Computer Science

Advisors/Committee Members: Fokkink, R. (mentor), Olsder, G.J. (mentor).

▼ 

Esforços físicos prolongados em ritmo dinâmico parecem promover menor demanda metabólica, estresse fisiológico e cardiovascular comparado a tarefas em ritmo constante. Contudo, os mecanismos não são completamente descritos. Além disso, sugere-se que o tempo que o indivíduo é capaz de suportar um exercício em intensidade máxima (TLim[FCmax]) correlaciona-se com o desempenho no ciclismo. Assim, os objetivos do presente estudo foram verificar como a estratégia de prova (EP) influencia nas respostas fisiológicas, no controle autonômico cardiovascular e no desempenho de tarefas aeróbias subseqüentes. Adicionalmente, verificar se o Lim[FCmax] correlaciona-se com o desempenho em teste contrarelógio de 3 km (CR3KM). Participaram desse estudo oito ciclistas treinados masculinos. Após avaliações antropométricas e familiarização com os cicloergômetros, os indivíduos foram submetidos: (i) teste máximo progressivo para determinação da potência aeróbia máxima e dos limiares metabólicos; (ii) teste TLim[FCmax]; (iii) teste de 20 km adotando diferentes EP, mas mantendo a potência média em todas as sessões; (iv) teste CR3KM realizado 30 minutos após as EP. A frequência cardíaca (FC), a variabilidade da FC, a percepção de esforço (PSE) e o lactato sanguíneo [Lac] foram registrados em todas as situações experimentais. A transformada de Fourier e a amostragem entrópica foram empregadas para analisar a VFC, ao passo que a FC foi descrita por função exponencial. Adicionalmente, a ANOVA two way (estratégia de prova x distância) e a correlação produto momento de Pearson foram utilizadas para comparações estatísticas. Para todas as análises, foi assumido um p < 0,05. Os principais achados foram que o TLim[FCmax] não correlacionou-se o desempenho do CR3KM, a EP não modificou o teste CR3KM subseqüente. No entanto, houve menores incrementos de [Lac], FC e PSE na EP positiva. Possivelmente o início rápido na EP positiva reduz o déficit anaeróbio de oxigênio, reduzindo a contribuição glicolítica nesse período inicial. Finalmente, a VFC apresentou menor complexidade imediatamente após a tarefa, comparado ao repouso e aos minutos finais de recuperação, indicando maior redundância do sistema na tentativa de evitar eventos catastróficos ao organismo

Prolonged physical efforts in variable pacing promote lower metabolic demand, physiological and cardiovascular stress compared with workouts in even pacing. However, the mechanisms is not completely understanding. Additionally, one suggests that the period of time that someone can support exercises in maximal intensity (TLim[FCmax]) could be correlate with performance on the cycling. Thus, the objectives of this study were verified if the pacing strategy (EP) could influence the physiological responses, cardiovascular autonomic control and the performance of the subsequent aerobic exercises. Additionally, to verify the correlation between TLim[FCmax] with the performance on time trials of 3 km (CR3KM). Eight male trained cyclists took part of this study. After anthropometric tests and familiarization…

Advisors/Committee Members: Pereira, Benedito.

▼ This thesis aimed to investigate the way in which distance runners modulate their speed in an effort to understand the key processes and determinants of speed selection when encountering hills in natural outdoor environments. One factor which has limited the expansion of knowledge in this area has been a reliance on the motorized treadmill which constrains runners to constant speeds and gradients and only linear paths. Conversely, limits in the portability or storage capacity of available technology have restricted field research to brief durations and level courses. Therefore another aim of this thesis was to evaluate the capacity of lightweight, portable technology to measure running speed in outdoor undulating terrain. The first study of this thesis assessed the validity of a non-differential GPS to measure speed, displacement and position during human locomotion. Three healthy participants walked and ran over straight and curved courses for 59 and 34 trials respectively. A non-differential GPS receiver provided speed data by Doppler Shift and change in GPS position over time, which were compared with actual speeds determined by chronometry. Displacement data from the GPS were compared with a surveyed 100m section, while static positions were collected for 1 hour and compared with the known geodetic point. GPS speed values on the straight course were found to be closely correlated with actual speeds (Doppler shift: r = 0.9994, p < 0.001, Δ GPS position/time: r = 0.9984, p < 0.001). Actual speed errors were lowest using the Doppler shift method (90.8% of values within ± 0.1 m.sec -1). Speed was slightly underestimated on a curved path, though still highly correlated with actual speed (Doppler shift: r = 0.9985, p < 0.001, Δ GPS distance/time: r = 0.9973, p < 0.001). Distance measured by GPS was 100.46 ± 0.49m, while 86.5% of static points were within 1.5m of the actual geodetic point (mean error: 1.08 ± 0.34m, range 0.69-2.10m). Non-differential GPS demonstrated a highly accurate estimation of speed across a wide range of human locomotion velocities using only the raw signal data with a minimal decrease in accuracy around bends. This high level of resolution was matched by accurate displacement and position data. Coupled with reduced size, cost and ease of use, the use of a non-differential receiver offers a valid alternative to differential GPS in the study of overground locomotion. The second study of this dissertation examined speed regulation during overground running on a hilly course. Following an initial laboratory session to calculate physiological thresholds (VO2 max and ventilatory thresholds), eight experienced long distance runners completed a self- paced time trial over three laps of an outdoor course involving uphill, downhill and level sections. A portable gas analyser, GPS receiver and activity monitor were used to collect physiological, speed and stride frequency data. Participants ran 23% slower on uphills and 13.8% faster on downhills compared with level sections. Speeds on level…

▼ Exercise or activity in high ambient temperatures offers a particular challenge to the thermoregulatory system. It is likely that mechanisms such as sweat evaporation alone are not sufficient for maintaining body temperature within a safe limit (~36.5-38.5˚C) and below 40˚C, which may result in impaired physiological function and performance. Exogenous cooling may be of benefit prior to, during and after events that place increased thermal strain due to increased metabolic heat production and elevated environmental temperatures upon the thermoregulatory system. Conversely, in situations where it is not possible to maintain body temperature via either continued physical activity or elevated ambient temperatures, exogenous heating may be required in order to allow optimal physiological performance. Few studies have directly aligned cooling devices with data detailing effective target regions for cooling to allow a pre-cooling garment to be of minimal weight but maximal cooling efficiency. Conversely, no study has considered the effect of muscle temperature maintenance during rest periods on subsequent power-based activities. The aim of this thesis was to determine ways in which body temperature manipulation is capable of improving exercise performance in both power and endurance-based events. It was hypothesised that the manipulation of body temperature will result in subsequent changes in body temperature that would improve performance. Specifically, the use of pre-cooling would result in a reduction of body temperature and improve endurance exercise performance. Conversely, maintaining Tm following warm up completion would have a beneficial effect on sprint and power related performance. Study one set out to determine differences in regional body heat loss in 12 individual anatomical zones using a water perfused suit. Data obtained from this initial study allowed for the specific targeting of regions that were identified as having high rates of heat loss in subsequent studies that focused on pre-cooling and performance. The anatomical regions identified as having high potential affinity for heat exchange with the surrounding environment and cooling devices were the hands, forearms, upper and lower back and torso. Subsequent studies demonstrated that cooling of these areas was capable of lowering thermal sensation and improving thermal comfort prior to and during exercise in moderate environmental conditions (24˚C, 50% RH). In these moderate conditions, there was no statistically significant improvement in treadmill based self-paced 5000m running performance. However, in hot conditions (35˚C 50% RH), the use of a cooling vest and sleeves did yield a significant improvement in cycling time trial performance, which equated to 4.8%. This leads to the suggestion that there may be a threshold ambient temperature, above which pre-cooling becomes an important tool in maximizing performance potential. A parallel area of investigation, on the other side of the temperature spectrum, was the effect of muscle temperature…

▼ 

Apesar de descrito em diversos esportes, as estratégias de prova não foram descritas em uma prova de mountain bike cross country (XCO). Em conjunto, uma melhor compreensão das respostas emocionais e cognitivas contribui para um melhor entendimento do esporte. A presente dissertação tratará desses dois temas em dois diferentes artigos. O artigo 1 teve como objetivo comparar e classificar as estratégias de prova adotadas por sujeitos com diferentes níveis de desempenho num teste de desempenho simulado (TDS) O objetivo do estudo 2 foi descrever a resposta do humor ao longo do TDS, além de analisar o relacionamento da percepção subjetiva de esforço (PSE) em função da distância completada e da potência média produzida a cada volta (WSPT). No artigo 1, ciclistas de nível nacional e regional de XCO (n=20, 32,36,5 anos, 175.75,9cm, 69,25,6kg, 297,621,8Wmax e 65,75,4mL.kg.min) participaram de uma competição simulada em um cicloergômetro eletrônico (Computrainer ), composta por 4 voltas em um circuito. Os atletas foram divididos em dois grupos (alto e baixo) baseados no tempo de desempenho e instruídos a realizarem o percurso o mais rápido que pudessem. Não houve interação para o tempo da volta (P=0,169) potência produzida absoluta (P=0,719) e relativa (P=0,607), PSE (P=0,182) e frequência cardíaca (P=0,125). No artigo 2, ciclistas de nível nacional e regional de XCO (n=19, 32,26,5 anos, 174,95,4cm, 67,86,5kg, 295,821,1Wmax e 65,34,9mL.kg.min) realizaram a mesma simulação de desempenho descrita no método do estudo 1. No último km de cada volta foi utilizada a escala de perfil de estado de humor (POMS) e a escala CR100 para a quantificação da PSE. Foram observadas a diminuição no vigor (P=0,049) e aumento na fadiga (P=0,000) e no distúrbio total de humor (DTH) (P=0,014). Além disso encontramos boa correlação entre a PSE e a distância percorrida (r=0,999 P=0,000), o %tempo (r=0,999 P=0,000) e a W (r=0,969 P=0,030). Concluímos a partir dos nossos resultados que o nível de desempenho não afetou a estratégia, e que o humor foi afetado negativamente em nível competitivo, confirmado pelo aumento do DTH assim como pelo aumento do cofator fadiga do POMS e da PSE ao longo do TDS.

Despite described in many sports, pace strategy have not been described in mountain bike cross country race (XCO). Together, a better comprehension of cognitive and emotional responses contribute for a better understanding of sport. This dissertation will address these two issue on two different articles. The purpose of article 1 was to compare and classify the pace strategy adopted by subjects with different levels of performance on a simulated performance test (SPT). The purpose of article 2 was to describe the mood responses over a SPT, in addition to analyze the relationship of rating of perceived exertion (RPE) against distance covered and mean power output of each lap (WSPT). On the article 1, cyclists of regional and national level of XCO (n=20, 32,36,5 anos, 175.75,9cm, 69,25,6kg, 297,621,8Wmax e 64,94,8mL.kg-1.min-1), participated of a simulated…

Advisors/Committee Members: Andréa Camaz Deslandes, Tony Meireles dos Santos, Flávio de Oliveira Pires.

▼ 

O sistema visual exerce importante papel para o reconhecimento do ambiente externo e para estabelecer relações entre objetos, tempo e espaço. Além disso, ele está relacionado com o controle e o desempenho motor. O objetivo deste estudo foi verificar se a privação de luz ambiente alteraria o desempenho e as respostas fisiológicas e psicológicas durante dois modelos de exercício, um fechado e um aberto. Onze ciclistas formaram o grupo de exercício fechado (GEF) e completaram um teste de 20 km, enquanto doze indivíduos ativos formaram o grupo de exercício aberto (GEA) e executaram um teste de potência constante até a exaustão (TWC). Após teste incremental máximo, GEF e GEA realizaram exercício na presença (controle) ou privação (experimental) de luz ambiente, em ordem balanceada. Respostas de desempenho, VE, VO2, VCO2 RER, FC, eletromiografia do músculo vato lateral (EMG), percepção subjetiva de esforço (PSE) e pensamento associado ao exercício (PAE) foram obtidas durante, e no ponto final do exercício, em ambas as condições. O tempo total de exercício indicou a resposta de desempenho em GEF e GEA. As respostas das variáveis fisiológicas e psicológicas foram analisadas durante a realização, ou no ponto final do exercício. A média das respostas geradas durante os 20 km no GEF, e as respostas obtidas no mesmo tempo absoluto do TWC no GEA, pareado pelo menor tempo de exaustão atingido no teste, indicaram as respostas durante a execução do exercício. As respostas obtidas nos 5 segundos finais de cada exercício indicaram as respostas do ponto final do GEF e GEA. A taxa de incremento na PSE foi calculada em GEF e GEA, e o erro de predição da distância real percorrida no teste de 20 km foi obtido no GEF. No GEF, não houve efeito da privação de luz sobre o tempo para completar o teste de 20 km, porém a privação de luz gerou menores respostas (P< 0,01) na VE, VO2, VCO2, EMG e PAE, quando comparada ao controle. No ponto final do exercício, nenhuma diferença foi verificada entre as condições. A privação de luz não alterou a taxa de elevação da PSE ou o erro de predição da distância percorrida. No GEA a privação de luz ambiente reduziu o tempo de exaustão (P< 0,05) no TWC e aumentou a resposta do VO2 e EMG (P< 0,05). Entretanto, não foi observado efeito da privação de luz na VE, VCO2 e FC. No ponto final do exercício observou-se menor EMG com a privação de luz (P< 0,03), mas nenhuma diferença nas demais variáveis foi observada. Maior taxa de elevação na PSE foi observada em ambiente privado de luz. Os resultados do presente estudo podem ser interpretados de acordo com a existência de um \"relógio biológico internoq̈ue calcula a duração tolerável do exercício de acordo com a aproximação ao ponto final do exercício, sugerindo que os efeitos da privação de luz sobre o desempenho possam depender da presença de um ponto final previamente conhecido

The visual system plays an important role for the environment recognition as well as to set objects, time and space relationships. Furthermore, the visual system is related to the motor…

Advisors/Committee Members: Pires, Flávio de Oliveira.

▼ 

O objetivo do estudo foi examinar a influência de variáveis fisiológicas, perceptuais e mecânicas nas diferentes estratégias de corrida e no desempenho de atletas. Doze corredores especialistas em 5.000m realizaram: 1) um teste escalonado máximo para identificação do consumo máximo de oxigênio (VO2máx), velocidade de corrida associada ao VO2máx (vVO2máx), pico de velocidade em esteira (PVE) e velocidade de corrida associada ao limiar anaeróbio (vLAn); 2) uma prova de corrida de 5.000m avaliada a cada trecho (n = 5) de 1.000m em pista de atletismo para registro da frequência cardíaca (FC), percepção subjetiva de esforço (PSE) e velocidade de corrida. Os sujeitos foram divididos em dois grupos: saída lenta (SL) e saída rápida (SR) de acordo com a estratégia adotada, que por sua vez foi baseada na relação da velocidade de corrida no trecho inicial (Vel20%) com a velocidade média do teste de 5.000m. Os dados foram comparados entre os grupos de estratégia e posteriormente entre os trechos da prova esportiva para cada variável analisada. A velocidade de corrida no trecho inicial (SL = 16,9km.h-1 e SR = 19,1km.h-1) e no trecho final (SL = 19,1km.h-1 e SR = 16,7km.h-1) foi significantemente diferente (p < 0,05), o mesmo não ocorreu com a PSE. Já a FC nos três últimos trechos (SL = 185; 188 e 195 bpm e SR = 191; 193 e 200 bpm) apresentou diferença significante (p < 0,05) entre os grupos avaliados. Adicionalmente, foram encontradas associações entre PVE e Vel20% (rs = 0,57; p < 0,05), vVO2máx e Vel20% (rs = 0,55; p < 0,05), e entre vLAn e Vel20% (rs = 0,54; p < 0,05). Quando os parâmetros de desempenho (FC, PSE e velocidade de corrida) foram comparados dentro de cada grupo, apresentaram diferença significante (p < 0,05) entre todos os trechos analisados do teste. Dessa forma, concluímos haver influência da estratégia adotada no início da prova sobre a regulação da velocidade e sobre o desempenho na corrida de 5.000m, sobretudo, quando relacionada a parâmetros fisiológicos, perceptuais e mecânicos

The objective of this study was to examine the influence of physiological, perceptual and mechanical parameters in different pacing strategies and performance of athletes. Twelve runners performed: 1) a test scaled maximal to identify the maximum oxygen uptake (VO2max), running velocity associated with VO2max (vVO2max), peak treadmill velocity (PTV) and running velocity associated with the anaerobic threshold (vAnT); 2) a time trial evaluated in each 1,000m in the track to record heart rate (HR), rating of perceived exertion (RPE) and running speed. The subjects were divided into two groups: slow start (SS) and fast start (FS) in accordance with the strategy used, which in turn was based on the ratio of the velocity of the initial split (Vel20%) with the speed average of the time trial. Data were compared between groups of the pacing strategy for each variable analyzed. The velocity at the initial split (SS = 16.9 km.h-1 and FS = 19.1 km.h-1) and in the final split (SS = 19.1 km.h-1 and FS = 16.7 km.h-1) was different significantly…

Advisors/Committee Members: Kiss, Maria Augusta Peduti Dal Molin.