Hypohydration during Prolonged Exercise in the Heat

Hypohydration during Prolonged Exercise in the Heat This thesis investigated the effect of hypohydration during prolonged exercise in the heat and the adjustments in the thermoregulatory and cardiovascular control. Four inter-related studies were undertaken. Study One was an observational field study designed to determine the hydration status and practices of elite Kenyan runners (n=11) during competitive distance running events in a tropical environment. Our results show that the elite runners completed their races in warm, very humid climatic conditions with ~3% body weight (BW) loss. They completed their races as the fast finishers in this present study but ran slower than they were capable because of the prevailing heat and humidity. Study Two investigated the effects of hypohydration and simulated hyperhydration on running economy. It was demonstrated that hypohydration did not reduce the oxygen cost of running proportionally with the BW deficit incurred and simulated hyperhydration did not increase the oxygen cost of running proportionally with the added gross weight of the runners. In Study Three, the effects of hypohydration on prolonged treadmill running performance in the well controlled hot and cool conditions of a climatic chamber were investigated in 8 male runners. A diuretic was used to induce ~3% BW deficit. Mild dehydration (~4.5% BW loss) was shown to have a significant effect on endurance performance in hot conditions. However, this level of dehydration did not adversely affect endurance performance in cool conditions. Study Four addressed the question of whether enhanced heat shock protein (HSP) expression induced via glutamine supplementation is beneficial in offsetting the deleterious effect of hypohydration on exercise performance. The present study demonstrates alanyl-glutamine ingestion confers protection and enhances plasma HSP 72 expression. Furthermore, ingestion of alanyl-glutamine was associated with an increased time to exhaustion during hot and hypohydrated conditions

Differences in psychosocial determinants by gender and physical activity index among undergraduates

Majority of Malaysians do not meet the recommendation of adequate and regular physical activity, with about 61.4 % (aged 15 and above) considered inactive. This study examined the differences of psychosocial determinants of physical activity in undergraduates according to gender and physical activity index category. Self-efficacy Assessment, Social Support for Exercise, Motivation and Physical Activity Enjoyment Scales were used to measure the psychosocial determinants of physical activity. The Physical Activity Index (PAI) was determined by multiplying exercise intensity, duration and frequency. The total PAI score was categorized as 'Needs improvement' [NI], 'Fair' [F], 'Average' [A], 'Good' [G] and 'Excellent' [E]. A total of 359 undergraduates (male = 74.4%, female = 25.6%) were conveniently surveyed. Result in physical index category revealed that 25% of the undergraduates each was in the 'fair' and 'average' category. About 15% of the undergraduates needs improvement and 34.8% was in the 'good' and 'excellent' category. Inferential statistics analyses showed psychosocial determinants of 'self-efficacy', 'exercise enjoyment', 'motivation' and 'support from family' were significant according to gender. Males involved in physical activity due to 'self-efficacy', 'motivation' and 'enjoyment' while females were more influenced by family support. Significant results on PAI category and psychosocial determinants were shown in self-efficacy, social support from friends, motivation, and exercise enjoyment. For 'self-efficacy' and 'social support from friend' factors, the 'Need Improvement' group had low self-efficacy and low social support from friends. However, for the 'motivation' and 'exercise enjoyment' factors, the 'Needs Improvement' was more motivated and enjoyed exercise more than other groups.La mayoría de Malasios no cumplen las recomendaciones sobre una actividad física adecuada y regular, ya que 61.4% (edad ≥ 15 años) son considerados inactivos. Este estudio examinó las diferencias de los determinantes psicosociales de la actividad física en estudiantes de grado según su género y su categoría del nivel de actividad física. Para medir los determinantes de actividad física se aplicaron: Evaluación de la Auto-eficacia, Evaluación del Soporte Social al Ejercicio, Escalas de Motivación y de Disfrute de la Actividad Física. El índice de Actividad Física (IAF) fue determinado multiplicando la intensidad de ejercicio, su duración y frecuencia. La puntuación total del IAF fue categorizada como: 'Necesita Mejorar' [NM], 'Justo' [J], 'Medio' [M], 'Bueno' [B] y 'Excelente' [E]. Un total de 359 estudiantes por conveniencia (hombres = 74.4%, mujeres = 25.6%) fueron encuestados. Los resultados de las categorías del IAF mostraron que un 25% de los estudiantes se encontraba en la categoría 'justo' y 'medio'; un 15% de los estudiantes necesita mejorar y un 34.8% se encontraba en las categorías 'bueno' y 'excelente'. El análisis estadístico inferencial mostró que los determinantes psicosociales de 'auto-eficacia', 'disfrute del ejercicio', motivación' y 'soporte de la familia' eran significativos en relación al género. Los hombres se involucraban en actividad física debido a 'auto-eficacia', 'motivación' y 'disfrute' mientras que las mujeres estaban más influenciadas por el soporte familiar. Se obtuvieron resultados significativos en la categoría IFA y determinantes psicosociales tanto en auto-eficacia como en soporte de los amigos, motivación y disfrute del ejercicio. Para los factores 'auto-eficacia' y 'soporte social de los amigos', el grupo 'Necesita Mejorar' tenía una baja auto-eficacia y bajo soporte social de los amigos. Sin embargo, para los factores 'motivación' y 'disfrute del ejercicio', el grupo 'Necesita Mejorar' estaba más motivado y disfrutaba más del ejercicio que los otros grupos

Changes in heart rate variability and post exercise blood pressure from manipulating load intensities of resistance-training

Background: The isolated effect of resistance training (RT) on heart rate variability (HRV) and blood pressure (BP) is crucial when prescribing suitable training programmes for healthy individuals. Objective: The purpose of this study was to compare BP and HRV responses in physically active men after an acute RT session with loads of 5-, 10- or 15-repetition maximums (5RM, 10RM and 15RM). Method: Eighty-one men (age: 21.6±1.1yr; body mass: 74.1±5.8 kg; height: 175.3 ±7.1cm) who performed moderate to vigorous physical activities for at least 30 min a day on most days of the week participated in this study. After the of 5RM loads for the bent-over row (BR), bench press (BEP), Dead-lift (DL) and squats (SQ), participants were divided into three training load groups (15RM = GrpL, 10RM = GrpM or 5RM = GrpH). During the experimental session, each group (n=27) performed 3 sets for each of the four exercise, with 2-min rest intervals between sets and exercises with their assigned training load. BP and HRV were measured prior to, immediately after, and at 15-min intervals until two hours post-experiment. Results: All three groups attained improved BP (p = .001) reductions and longer HRV (p = .0001) changes after an acute exercise session but the GrpM (10RM) and and GrpL (15RM) performed better than GrpH (5RM). Conclusion: Strength and conditioning professionals may prescribe exercises with 10-15RM loads if the aim is to obtain an acute reduction in BP after an RT session

Hypohydration during prolonged exercise in the heat / Ler Hui Yin

This thesis investigated the effect of hypohydration during prolonged exercise in the heat and the adjustments in the thermoregulatory and cardiovascular control. Four inter-related studies were undertaken. Study One was an observational field study designed to determine the hydration status and practices of elite Kenyan runners (n=11) during competitive distance running events in a tropical environment. Our results show that the elite endurance runners completed their races in warm, very humid climatic conditions with ~3% body weight (BW) loss. They completed their races as the fast finishers in this present study but ran slower than they were capable because of the prevailing heat and humidity. Interestingly, they were able to compensate well by increasing the sweating rate regardless of the amount of fluid ingested or percentage of BW loss in warm conditions. Study Two investigated the effects of hypohydration and simulated hyperhydration on running economy. It was demonstrated that (1) hypohydration did not reduce the oxygen cost of running proportionally with the BW deficit incurred (D3 and D4) and (2) simulated hyperhydration did not increase the oxygen cost of running proportionally with the added gross weight of the runners (AW3 and AW4). Thus despite incurring a decrease in BW, none of the runners in the present study gained any beneficial effect in running economy with hypohydration. The additional oxygen cost was minimised during simulated hyperhydration trials with the added weight evenly distributed around the torso which may be offset by an added contribution from the series and parallel elastic component of muscles and tendons at no additional metabolic cost. In Study Three, the effects of hypohydration on prolonged treadmill running performance in the well controlled hot and cool conditions of a climatic chamber were investigated in 8 male runners. A diuretic (Lasix® 1 mg /kg BM) was used to induce ~3% BW deficit. Mild dehydration (~4.5% BW loss) was shown to have a significant effect on endurance performance in hot conditions. iv However, this level of dehydration did not adversely affect endurance performance in cool conditions. Study Four addressed the question of whether enhanced heat shock protein (HSP) expression induced via glutamine supplementation is beneficial in offsetting the deleterious effect of hypohydration on exercise performance. The study further investigated whether alanyl glutamine administration offsets the reported prolonged exercise-induced decrease in plasma glutamine concentration. The present study demonstrates alanyl-glutamine ingestion confers protection and enhances plasma HSP 72 expression. Furthermore, ingestion of alanyl-glutamine was associated with an increased time to exhaustion during hot and hypohydrated conditions. In conclusion, this thesis showed that hypohydration (~ 3% BW) placed the circulatory and thermoregulatory systems under considerable physiological strain during prolonged exercise performance in the heat. However, the alanyl-glutamine ingestion conferred protection and enhanced plasma HSP 72 expression which improves thermotolerance in the heat

Do Acute Changes In Gross Body Weight Effect Running Economy And Cardiorespiratory Responses?

Running economy is expressed as oxygen uptake (VO2) or energy cost relative to body weight when running at submaximal velocities. Theoretically the loss of bodyweight (2-3% bodyweight) associated with sweating and dehydration should reduce the VO2 cost of running. To avoid the confounding factors associated with dehydration (e.g., increase in core temperature), we investigated the sensitivity of the VO2 cost of running with added weight inserted in a \u201cweight jacket\u201d worn around the torso of the body. Running economy was tested in thermoneutral conditions with subjects in a euhydrated state

Differences in psychosocial determinants by gender and physical activity index among undergraduates

Majority of Malaysians do not meet the recommendation of adequate and regular physical activity, with about 61.4 % (aged 15 and above) considered inactive. This study examined the differences of psychosocial determinants of physical activity in undergraduates according to gender and physical activity index category. Self-efficacy Assessment, Social Support for Exercise, Motivation and Physical Activity Enjoyment Scales were used to measure the psychosocial determinants of physical activity. The Physical Activity Index (PAI) was determined by multiplying exercise intensity, duration and frequency. The total PAI score was categorized as 'Needs improvement' [NI], 'Fair' [F], 'Average' [A], 'Good' [G] and 'Excellent' [E]. A total of 359 undergraduates (male = 74.4%, female = 25.6%) were conveniently surveyed. Result in physical index category revealed that 25% of the undergraduates each was in the 'fair' and 'average' category. About 15% of the undergraduates needs improvement and 34.8% was in the 'good' and 'excellent' category. Inferential statistics analyses showed psychosocial determinants of 'self-efficacy', 'exercise enjoyment', 'motivation' and 'support from family' were significant according to gender. Males involved in physical activity due to 'self-efficacy', 'motivation' and 'enjoyment' while females were more influenced by family support. Significant results on PAI category and psychosocial determinants were shown in self-efficacy, social support from friends, motivation, and exercise enjoyment. For 'self-efficacy' and 'social support from friend' factors, the 'Need Improvement' group had low self-efficacy and low social support from friends. However, for the 'motivation' and 'exercise enjoyment' factors, the 'Needs Improvement' was more motivated and enjoyed exercise more than other groups.La mayoría de Malasios no cumplen las recomendaciones sobre una actividad física adecuada y regular, ya que 61.4% (edad ≥ 15 años) son considerados inactivos. Este estudio examinó las diferencias de los determinantes psicosociales de la actividad física en estudiantes de grado según su género y su categoría del nivel de actividad física. Para medir los determinantes de actividad física se aplicaron: Evaluación de la Auto-eficacia, Evaluación del Soporte Social al Ejercicio, Escalas de Motivación y de Disfrute de la Actividad Física. El índice de Actividad Física (IAF) fue determinado multiplicando la intensidad de ejercicio, su duración y frecuencia. La puntuación total del IAF fue categorizada como: 'Necesita Mejorar' [NM], 'Justo' [J], 'Medio' [M], 'Bueno' [B] y 'Excelente' [E]. Un total de 359 estudiantes por conveniencia (hombres = 74.4%, mujeres = 25.6%) fueron encuestados. Los resultados de las categorías del IAF mostraron que un 25% de los estudiantes se encontraba en la categoría 'justo' y 'medio'; un 15% de los estudiantes necesita mejorar y un 34.8% se encontraba en las categorías 'bueno' y 'excelente'. El análisis estadístico inferencial mostró que los determinantes psicosociales de 'auto-eficacia', 'disfrute del ejercicio', motivación' y 'soporte de la familia' eran significativos en relación al género. Los hombres se involucraban en actividad física debido a 'auto-eficacia', 'motivación' y 'disfrute' mientras que las mujeres estaban más influenciadas por el soporte familiar. Se obtuvieron resultados significativos en la categoría IFA y determinantes psicosociales tanto en auto-eficacia como en soporte de los amigos, motivación y disfrute del ejercicio. Para los factores 'auto-eficacia' y 'soporte social de los amigos', el grupo 'Necesita Mejorar' tenía una baja auto-eficacia y bajo soporte social de los amigos. Sin embargo, para los factores 'motivación' y 'disfrute del ejercicio', el grupo 'Necesita Mejorar' estaba más motivado y disfrutaba más del ejercicio que los otros grupos

Changes in Heart Rate Variability and Post Exercise Blood Pressure from Manipulating Load Intensities of Resistance-Training

Background: The isolated effect of resistance training (RT) on heart rate variability (HRV) and blood pressure (BP) is crucial when prescribing suitable training programmes for healthy individuals. Objective: The purpose of this study was to compare BP and HRV responses in physically active men after an acute RT session with loads of 5-, 10- or 15-repetition maximums (5RM, 10RM and 15RM). Method: Eighty-one men (age: 21.6±1.1yr; body mass: 74.1±5.8 kg; height: 175.3 ±7.1cm) who performed moderate to vigorous physical activities for at least 30 min a day on most days of the week participated in this study. After the of 5RM loads for the bent-over row (BR), bench press (BEP), Dead-lift (DL) and squats (SQ), participants were divided into three training load groups (15RM = GrpL, 10RM = GrpM or 5RM = GrpH). During the experimental session, each group (n=27) performed 3 sets for each of the four exercise, with 2-min rest intervals between sets and exercises with their assigned training load. BP and HRV were measured prior to, immediately after, and at 15-min intervals until two hours post-experiment. Results: All three groups attained improved BP (p = .001) reductions and longer HRV (p = .0001) changes after an acute exercise session but the GrpM (10RM) and and GrpL (15RM) performed better than GrpH (5RM). Conclusion: Strength and conditioning professionals may prescribe exercises with 10-15RM loads if the aim is to obtain an acute reduction in BP after an RT session

Radiological and clinical outcome of selective thoracic fusion for patients with Lenke 1C and 2C adolescent idiopathic scoliosis with a minimum follow-up of 2 years

Background Context: In Lenke 1C and 2C curves, the choice between selective thoracic fusion (STF) versus non-selective thoracic fusion as the optimal surgical treatment is controversial. Objective: This study aimed to assess the radiological and clinical outcome of patients with Lenke 1C and 2C curves treated with STF. Study Design: This is a retrospective study. Patient Sample: A total of 44 patients comprised the study sample. Methods: Forty-four patients with Lenke 1C and 2C curves with adolescent idiopathic scoliosis who underwent STF were reviewed. Radiological parameters and Scoliosis Research Society (SRS)-22r scores were assessed preoperatively, postoperatively, and on final follow-up. The incidence of coronal decompensation, lumbar decompensation, and adding-on phenomenon were reported. Results: Mean follow-up duration was 45.1±12.3 months and mean age was 17.0±5.1 years. The preoperative middle thoracic and thoracolumbar/lumbar (MT:TL/L) Cobb angle ratio was 1.4±0.3 and the MT:TL/L apical vertebra translation (AVT) ratio was 1.6±0.8. Final follow-up coronal balance was −13.0±11.5 mm, main thoracic AVT was 6.9±11.8 mm, and lumbar AVT was −20.4±13.8 mm (p<.05). Lumbar Cobb angle improved from 47.5°±7.8° to 24.9°±8.2° after operation and 23.3°±9.8° at final follow-up. The spontaneous lumbar curve correction rate was 50.9%. There were 9 patients (20.5%) who had coronal decompensation, 4 patients (9.1%) who had lumbar decompensation, and 11 patients (25.0%) who had adding-on phenomenon. We did not perform any revision surgery. The SRS-22r scores improved significantly in the overall scores, self-image, and mental health domain. Conclusions: Selective thoracic fusion led to improvement in the radiological and clinical outcome for patients with Lenke 1C and 2C. Although no patients required revision surgery, the rate of coronal decompensation, lumbar decompensation, and adding-on phenomenon are significant