Oxygen consumption and muscle activation patterns during constant load exercise

The collective purpose of these two studies was to determine a link between the V02 slow component and the muscle activation patterns that occur during cycling. Six, male subjects performed an incremental cycle ergometer exercise test to determine asub-TvENT (i.e. 80% of TvENT) and supra-TvENT (TvENT + 0.75*(V02 max - TvENT) work load. These two constant work loads were subsequently performed on either three or four occasions for 8 mins each, with V02 captured on a breath-by-breath basis for every test, and EMO of eight major leg muscles collected on one occasion. EMG was collected for the first 10 s of every 30 s period, except for the very first 10 s period. The V02 data was interpolated, time aligned, averaged and smoothed for both intensities. Three models were then fitted to the V02 data to determine the kinetics responses. One of these models was mono-exponential, while the other two were biexponential. A second time delay parameter was the only difference between the two bi-exponential models. An F-test was used to determine significance between the biexponential models using the residual sum of squares term for each model. EMO was integrated to obtain one value for each 10 s period, per muscle. The EMG data was analysed by a two-way repeated measures ANOV A. A correlation was also used to determine significance between V02 and IEMG. The V02 data during the sub-TvENT intensity was best described by a mono-exponential response. In contrast, during supra-TvENT exercise the two bi-exponential models best described the V02 data. The resultant F-test revealed no significant difference between the two models and therefore demonstrated that the slow component was not delayed relative to the onset of the primary component. Furthermore, only two parameters were deemed to be significantly different based upon the two models. This is in contrast to other findings. The EMG data, for most muscles, appeared to follow the same pattern as V02 during both intensities of exercise. On most occasions, the correlation coefficient demonstrated significance. Although some muscles demonstrated the same relative increase in IEMO based upon increases in intensity and duration, it cannot be assumed that these muscles increase their contribution to V02 in a similar fashion. Larger muscles with a higher percentage of type II muscle fibres would have a larger increase in V02 over the same increase in intensity.

Physiological aspects of the life cycle of the river lamprey, Lampetra fluviatilis L

The life cycle of the river lamprey, L. fluviatilis, is reviewed. The larval lamprey, or ammocoete, is a blind, filter-feeding animal, which normally lies concealed in the silt deposits of streams and rivers. After a period of 3-5 years in fresh water the ammocoete undergoes a metamorphosis in the summer months into a sexually immature, non-feeding stage known as the macrophthalia, which is active. This stage migrates downstream in late winter. It adopts a parasitic existence, in intertidal areas. After 18 months it returns to spawn in fresh water, after a final freshwater stage lasting up to 9 months. The river lamprey dies within a few days after the spawning period of 3-4 weeks, and none survive to spawn the following year.

Amino acids and endurance exercise

Provides information on a study which examined the role of amino acids during endurance exercise and the implications for sports nutrition and performance. Description of amino acid utilization during exercise; Function of glutamine; Cardiovascular function of L-arginine.<br />

Prescribing exercise for Osteoporosis

Osteoporosis is a major public health problem because of the morbidity and mortality associated with fracture. Minimizing the risk of fracture is the primary objective of osteoporosis management. The role of exercise in osteoporosis management is to increase and maintain peak bone density and reduce the rate of bone loss and the risk of falling. This article provides recommendations focusing on a life-span approach to minimizing the risk of fracture associated with osteoporosis. Osteoporosis prevention begins in childhood, when exercise can increase peak bone strength. In young adults, it can maintain peak bone mineral density. In elderly individuals, physical activity can slow bone loss and improve fitness and muscle strength, helping prevent falls and lower the risk of fracture. Exercise goals for individuals with osteoporosis should include reducing pain, increasing mobility, and improving muscle endurance, balance, and stability in order to improve the quality of life and reduce the risk of falling. Thus, exercise plays a significant part in reducing fractures in later life.<br />

Studies on dietary fibre : analysis, epidemiological and physiological aspects

This thesis involves an investigation in three areas; first, a study of an enzymatic-gravimetric method for the analysis of dietary fibre; second, a survey of dietary fibre intake in an area of a developing country, and finally, some observations on the functional aspects of gel-forming dietary fibre in the rat. A simple and rapid enzymatic-gravimetric assay for both soluble and insoluble dietary fibre has been critically investigated. Reference samples were also analysed by a more comprehensive, enzymatic gas chromatographic method to allow testing of the relative accuracy of the enzymatic-gravimetric method. The enzymatic-gravimetric method was found to be highly reproducible but gave a slightly higher value for total dietary fibre than the more comprehensive method. This discrepancy is probably due to the presence of small quantities of resistant starch and protein residue which are recovered in the enzymatic-gravimetric method. In the enzymatic-gas chromatographic method, protein residue is not measured, and resistant starch is estimated, but not counted as dietary fibre. The enzymatic-gravimetric method was applied to the analysis of foods commonly consumed in the Padang region of West Sumatra in Indonesia, in order to estimate dietary fibre intake in the region. Daily intakes of usual foods were estimated by use of a 24-hour recall procedure aided by food photographs to assist in the estimation of portion size. Samples of approximately 60 of the most commonly consumed foods were collected and analysed for dietary fibre. These appear to be the first data which report values for dietary fibre in Indonesion foods and they represent a significant improvement upon the existing data on crude fibre content. Knowledge of the amounts of foods usually consumed and their dietary fibre content allowed an estimation of usual intakes of dietary fibre. Fibre intake was found to be lower than in the developing countries of Africa and was comparable to intakes measured in the U.K. This is the first study to show that in this part of South East Asia, a developing country area using polished rice as a staple food, dietary fibre intakes are as low as in Western countries. Low intakes of fibre are believed to be related to the prevalence of a range of diseases and, in this study, preliminary data on the rates of non-infective, chronic diseases were collected from the two main hospitals in West Sumatra. Chronic, non-infectious diseases such as inguinal hernia, appendicitis, haemorrhoids, diabetes mellitus, hypertension and malignant neoplasms of the rectum are relatively frequent in West Sumatra. While no firm conclusions can be drawn from these data, they do show the possibility of a relationship between low intakes of dietary fibre and the prevalence of these diseases, and suggest that further investigation is necessary. Some observations were made of the effect of gel-forming dietary fibre on stomach emptying and intestinal transit rate in the rat. Xanthan gum was added to iso-osmotic solutions to produce increased viscosity and phenol sulphonphthalein (phenol red) was used as a non-absorbable marker. Gavage feeding of solutions with a range of viscosities was used to study the effect of viscosity on the rate of stomach emptying and intestinal transit. Increased viscosity was observed to slow gastro-intestinal transit and this provides one mechanism by which dietary fibre of the gel-forming type ray improve glucose tolerance.

Role of exercise in the development of bone strength during growth

Exercise during growth may increase peak bone mass; if the benefits are maintained it may reduce the risk of fracture later in life (1). It is hypothesised that exercise will preferentially enhance bone formation on the surface of cortical bone that is undergoing bone modeling at the time (2). Therefore, exercise may increase bone mass accrual on the outer periosteal surface during the pre- and peri-pubertal years, and on the inner endocortical surface during puberty (3). An increase in bone formation on the periosteal surface is, however, more effective for increasing bone strength than medullary contraction (4). While exercise may have a role in osteoporosis prevention, there is little evidential basis to support this notion. It is generally accepted that weight-bearing exercise is important, but it is not known how much, how often, what magnitude or how long children need to exercise before a clinically important increase in bone density is obtained. In this thesis, the effect of exercise on the growing skeleton is investigated in two projects. The first quantifies the magnitude and number of loads associated with and in a moderate and low impact exercise program and non-structured play. The second project examines how exercise affects bone size and shape during different stages of growth. Study One: The Assessment of the Magnitude of Exercise Loading and the Skeletal Response in Girls Questions: 1) Does moderate impact exercise lead to a greater increase in BMC than low impact exercise? 2) Does loading history influence the osteogenic response to moderate impact exercise? 3) What is the magnitude and number of loads that are associated with a moderate and low impact exercise program? Methods: Sixty-eight pre-and early-pubertal girls (aged 8.9±0.2 years) were randomised to either a moderate or low impact exercise regime for 8.5-months. In each exercise group the girls received either calcium fortified (-2000 mg/week) or non-fortified foods for the duration of the study. The magnitude and number of loads associated with the exercise programs and non-structured play were assessed using a Pedar in-sole mobile system and video footage, respectively. Findings: After adjusting for baseline BMC, change in length and calcium intake, the girls in the moderate exercise intervention showed greater increases in BMC at the tibia (2.7%) and total body (1.3%) (p ≤0.05). Girl's who participated in moderate impact sports outside of school, showed greater gains in BMC in response to the moderate impact exercise program compared to the low impact exercise program (2.5 to 4.5%, p ≤0.06 to 0.01). The moderate exercise program included -400 impacts per class, that were applied in a dynamic manner and the magnitude of impact was up to 4 times body weight. Conclusion: Moderate-impact exercise may be sufficient to enhance BMC accrual during the pre-pubertal years. However, loading history is likely to influence the osteogenic response to additional moderate impact exercise. These findings contribute towards the development of school-based exercise programs aimed at improving bone health of children. Study Two: Exercise Effect on Cortical Bone Morphology During Different Stages of Maturation in Tennis Players Questions: 1) How does exercise affect bone mass (BMC) bone geometry and bone strength during different stages of growth? 2) Is there an optimal stage during growth when exercise has the greatest affect on bone strength? Methods: MRI was used to measure average total bone, cortical and medullary areas at the mid- and distal-regions of the playing and non-playing humerii in 47 pre-, peri- and post-pubertal competitive female tennis players aged 8 to 17 years. To assess bone rigidity, each image was imported into Scion Image 4.0.2 and the maximum, minimum and polar second moments of area were calculated using a custom macro. DXA was used to measure BMC of the whole humerus. Longitudinal data was collected on 37 of the original cohort. Findings: Analysis of the entire cohort showed that exercise was associated with increased BMC and cortical area (8 to 14%), and bone rigidity (11 to 23%) (all p ≤0.05). The increase in cortical bone area was associated with periosteal expansion in the pre-pubertal years and endocortical contraction in the post-pubertal years (p ≤0.05). The exercise-related gains in bone mass that were accrued at the periosteum during the pre-pubertal years, did not increase with advanced maturation and/or additional training. Conclusion: Exercise increased cortical BMC by enhancing bone formation on the periosteal surface during the pre-pubertal years and on the endocortical surface in the post-pubertal years. However, bone strength only increased in response to bone acquisition on the periosteal surface. Therefore the pre-pubertal years appear to be the most opportune time for exercise to enhance BMC accrual and bone strength

Regulation of insulin signalling by exercise in skeletal muscle

Regular physical activity improves insulin action and is an effective therapy for the treatment and prevention of type 2 diabetes. However, little is known of the mechanisms by which exercise improves insulin action in muscle. These studies investigate the actions of a single bout of exercise and short-term endurance training on insulin signalling. Twenty-four hours following the completion of a single bout of endurance exercise insulin action improved, although greater enhancement of insulin action was demonstrated following the completion of endurance training, implying that cumulative bouts of exercise substantially increase insulin action above that seen from the residual effects of an acute bout of prior exercise. No alteration in the abundance and phosphorylation of proximal members of the insulin-signalling cascade in skeletal muscle, including the insulin receptor and IRS-1 were found. A major finding however, was the significant increase in the serine phosphorylation of a known downstream signalling protein, Akt (1.5 fold, p ≤0.05) following an acute bout of exercise and exercise training. This was matched by the observed increase in protein abundance of SHPTP2 (1.6 fold, p ≤0.05) a protein tyrosine phosphatase, in the cytosolic fraction of skeletal muscle following endurance exercise. These data suggest a small positive role for SHPTP2 on insulin stimulated glucose transport consistent with transgenic mice models. Further studies were aimed at examining the gene expression following a single bout of either resistance or endurance exercise. There were significant transient increases in IRS-2 mRNA concentration in the few hours following a single bout of both endurance and resistance exercise. IRS-2 protein abundance was also observed to significantly increase 24-hours following a single bout of endurance exercise indicating transcriptional regulation of IRS-2 following muscular contraction. One final component of this PhD project was to examine a second novel insulin-signalling pathway via c-Cbl tyrosine phosphorylation that has recently been shown to be essential for insulin stimulated glucose uptake in adipocytes. No evidence was found for the tyrosine phosphorylation of c-Cbl in the skeletal muscle of Zucker rats despite demonstrating significant phosphorylation of the insulin receptor and Akt by insulin treatment and successfully immunoprecipitating c-Cbl protein. Surprisingly, there was a small but significant increase in c-Cbl protein expression following insulin-stimulation, however c-Cbl tyrosine phosphorylation does not appear to be associated with insulin or exercise-mediated glucose transport in skeletal muscle.

Exercise, muscle glycogen and insulin action

The aim of this thesis was to investigate the influence of muscle glycogen concentration on whole body insulin stimulated glucose uptake in humans and to examine the potential signalling mechanisms responsible for enhanced insulin action in the post exercise period. Untrained male subjects were conditioned to achieve a range of muscle glycogen concentrations via acute exercise or a combination of exercise and diet. The influence of muscle glycogen content on whole body insulin stimulated glucose uptake was determined via hyperinsulinaemic / euglycaemic clamps conducted at rest, 30 min after exercise or 24 hours after exercise. Muscle glycogen content did not influence insulin mediated glucose disposal either 30 min or 24 hrs after exercise when compared with basal. Conventional insulin signalling to muscle glucose uptake and signalling through the p38 MAPK cascade was also largely unaltered by glycogen concentration. Muscle glycogen synthesis was significantly increased in heavily but not moderately glycogen depleted muscle 30 min after exercise. Enhanced muscle glycogen synthesis occurred in line with a significant increase in insulin stimulated GSK-3 serine phosphorylation. This finding suggests that enhanced insulin sensitivity of muscle glycogen synthesis following glycogen depleting exercise may be mediated via a pathway involving alterations in insulin stimulated GSK-3 phosphorylation. In summary, whilst glycogen influences insulin mediated GSK-3 phosphorylation and glycogen synthesis, the findings of the present series of investigations suggest that the role of muscle glycogen in the process of insulin stimulated glucose uptake may not be as important as previously theorised.

Effects of strength, flexibility and moderate intensity cardiovascular exercise on measures of fitness in sedentary women

The maintenance of functional physical fitness across the lifespan depends upon the presence or absence of disease, injury, and the level of habitual physical activity. The prevalence of sedentariness rises with increasing age culminating in 31% of elderly women being classified as leading a sedentary lifestyle. Exercise prescription that involves easily accomplished physical activity may result in the maintenance of mobility into old age through a reduction in the risk of premature death and disablement from cardiovascular disease and a reduction in the risk of falls and injuries from falls. It may be that short bouts of physical activity are more appealing to the sedentary and to those in full time employment than longer bouts, and it may be that short bouts of exercise, performed three times per day, can improve physical fitness. The purpose of this study was therefore to examine the problem: Does exercise session duration, initial cardiovascular fitness, and age group effect changes in functional physical fitness in sedentary women training for strength, flexibility and aerobic fitness? Twenty-three, sedentary women aged between 19 and 54 years who were employed at a major metropolitan hospital undertook six weeks of moderate intensity physical activity in one of two training groups. Participants were randomly allocated to either short duration (3 x 10 minute), or long duration (30 minute), exercise groups. The 3 x 10 minute group (n=13), participated in three, 10 minute sessions per day separated by at least 2 hours, 3 days per week. The 30 minute group (n=10), participated in three 30 minute sessions per week. The total amount of work was similar, with an average of 129 and 148 kcal training day for the 3 x 10 minute and 30 minute groups, respectively. The training program incorporated three walking and stair climbing courses for aerobic conditioning, a series of eleven static stretches for joint flexibility, and isotonic and isometric strength exercises for lower and upper body muscular strength. Measures of functional strength, functional flexibility and cardiovascular fitness were assessed prior to training, and immediately following the six week exercise program. A two way analysis of variance (Group x Time) was used to examine the effect of training and group on the dependent variables. The level of significance, 0.05 was adopted for all statistical tests. Mean hand grip strength showed for both groups no significant change over time for the 3 x 10 minute group (30.7kg to 31.7kg) and 30 minute group (30.2kg to 32.4kg). Leg strength showed a trend for improvement (p=0.098) in both the 3 x 10 minute and 30 minute training groups representing a 15% and 18% improvement, respectively. Combined right and left neck rotation significantly improved in the 3 x 10 minute group (82.8° to 92.0°) and 30 minute group (82.5° to 91.5°). Wrist flexion and extension improved significantly in 3 out of the 4 measurements. Left wrist flexion improved significantly by an average of 7.0% for the 3 x 10 minute and 4.9% for the 30 minute group. Right and left wrist extension improved significantly in the 3 x 10 minute and 30 minute training groups (5.9% and 6.8%, respectively). Hip and spine flexibility improved 3.4cm (35.2cm to 38.6cm) in the 3 x 10 minute group, and 6.6cm (37.4cm to 44.0cm) in the 30 minute group. There was a significant improvement in cardiovascular fitness for both groups representing a 22% improvement in the 3 x 10 minute group (27.2 to 33.2 ml kg min), and a 25% improvement in the 30 minute group (27.5 to 34.4 ml -kg min). No significant difference was shown in the degree of improvement in cardiovascular fitness over six weeks of training for subjects of either low or moderate initial aerobic fitness. Grip strength showed no significant changes over time for either the young-aged (19-35 years) or middle-aged (36-54 years) groups. Leg strength showed a trend for improvement (p=0.093) in the young-aged group (63.5kg to 71.9kg) and middle-aged group (69.3kg to 85.8kg). Neck rotation flexibility improved a similar amount in both the young and middle aged groups representing an improvement of 9.9° and 8.0° respectively. There was significant improvement in two of the four measures of wrist flexibility. Hip and spine flexibility was significantly greater in the young-aged group compared to the middle-aged group (38.5cm and 30.7cm, respectively). There was a significant improvement in hip and spine flexibility over the six week training program representing an increase in reach of 6.5cm for the young age group and 4.9cm for the older group. The middle-aged subjects had significantly lower cardiovascular fitness than their younger peers, scoring 22.8 and 30.7 ml -kg min, respectively. Cardiovascular fitness improved a similar amount in both age groups representing a significant improvement of 23.8% and 28.1% for the younger-aged and middle-aged subjects, respectively. The findings of this study suggest that short bouts of exercise may be equally as effective as longer bouts of exercise for improving the flexibility and cardiovascular components of functional physical fitness in sedentary young and middle aged women. Additionally short bouts of exercise may be more attractive than longer bouts of exercise for the beginning exerciser as they may more easily fit into the busy lifestyle encountered by many people in today's society. Sedentary young and middle-aged women should benefit from static flexibility exercises designed to improve and/or maintain functional flexibility and thus maintain mobility and reduce the incidence of muscular injury. Regular, brisk walking, incorporating some stair climbing, is likely to be beneficial in improving cardiovascular health and perhaps also in improving leg strength, thereby helping to improve and maintain functional physical fitness for both young and middle-aged sedentary women.

Effect of exercise and protein on skeletal muscle inflammatory mediators

Intense exercise results in muscular inflammation. Molecular techniques were used to identify novel inflammatory proteins in human muscle. Males and females displayed different levels of exercise-induced inflammatory proteins. Interestingly, dairy protein supplements reduced these inflammatory proteins post-exercise. Increased dietary red meat consumption, with training, had no impact on muscle inflammation, although strength gain was improved.

Effects of vegetarianism and exercise on muscle creatine loading and gene expression

The results of this thesis indicate that vegetarianism and prior exercise can increase skeletal muscle creatine loading. The mechanisms by which these phenomena occur remain unknown but may be related to changes in the gene expression of a cellular pump within the muscle known as the &quot;creatine transporter&quot;.