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    Assessing the portability of the standard shiftwork index : the impact of shiftwork on New Zealand : television production sample : a thesis presented in partial fulfillment of the requirements for the degree of Master of Arts in Psychology at Massey University
    (Massey University, 1997) Goddard, Teresa Anita
    The portability of the Standard Shiftwork Index (SSI) and the impact of shiftwork was assessed on a sample of television production employees in Auckland, New Zealand. Sixty three respondents completed the SSI and reported a moderate impact of shiftwork on physical and psychological health and moderately high sleep disturbance. Social and domestic life yielded the greatest detrimental impact. Gender related coping strategies was the only significant difference within the sample. Chronic fatigue, somatic anxiety, general job satisfaction and disengagement were significantly related to intention to leave the organisation. Statistical analysis of effect size indicated equivalent levels of power in both the U.K and the present sample. Overall, the results for the present sample were comparable to the U.K sample, indicating the portability of the SSI to the present sample. Organisational restructuring was considered a potential moderator of the overall moderate impact of shiftwork on the sample.
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    Effects of power and radio frequency electromagnetic fields on human performance : a dissertation submitted in partial fulfillment for the degree of Doctor of Philosophy in Physiology, Massey University
    (Massey University, 2005) Mobberley, Glenis Anne
    Humans have been exposed to manmade electromagnetic fields (EMFs) since electricity was first harnessed in the 1800s. This exposure has accelerated in the last few decades with the widespread use of electrical appliances producing 50/60 Hz power frequency EMFs. With the advent of cellular phones (900 or 1800 MHZ) exposure frequencies have increased and wavelengths shortened. With this exposure has come a public concern over possible health effects from increasing exposure to EMFs, particularly in the radio frequency bands. Experiment One exposed 29 subjects to an EMF of 50 Hz, 100µT, pulsed (one second on/ one second off). Each subject attended at 12 p.m. and 12 a.m. on two consecutive days, a total of two control and two exposure sessions. Effects on salivary melatonin levels, and the cognitive parameters of working memory and attention were studied. Experiment Two exposed 50 subjects to almost the same protocol and experimental conditions. An additional control sample of saliva was obtained before each of the four sessions. There was no significant effect on attention or auditory working memory in either experiment. In Experiment One the presence of the EMF had no effect on salivary melatonin levels, including the subgroup of those with naturally low levels. In Experiment Two, a significant drop in melatonin levels was found for the day session, but only when compared to the same day control. This raised questions as to the reliability of using a separate day as a control due to excessive within-subject variation over the two days. There were no significant differences between male and female subjects in response to the EMF. Experiment Three investigated possible effects from a commercially available digital 900 MHz band cellular phone on melatonin levels, aural temperature, blood pressure, heart rate and the cognitive parameters of attention and memory. Forty-three subjects attended a single evening session. Two exposure sessions were surrounded by three control sessions. This was done to compensate for the natural change that occurs in melatonin levels, temperature and cardiac readings during an evening. Results were averaged for control sessions then compared to the average for the exposure sessions. A statistically significant rise in aural temperature was noted in both ears when the phone was operating. The difference was significantly greater on the side the phone was held. Scores in an attention test were also significantly lower when the phone was in use. The reduced attention level has implications for the safety of using of cellular phones whilst driving. Heating of the head may have biological consequences depending on the depth of penetration. There was no perceived effect on melatonin levels, no gender effects or effects on those with naturally low melatonin levels. Neither cardiac readings or numerical working memory were effected by exposure to a cellular phone.
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    The effects of prolactin on prolactin receptor gene expression and wool growth in Romney ewes : Doctor of Philosophy in Animal Science at Massey University
    (Massey University, 2003) Montenegro, Renata
    The effect of exogenous prolactin on prolactin receptor (PRLR) gene expression and wool growth in pregnant and non-pregnant Romney ewes was assessed. Three experiments were performed where exogenous prolactin was administered by subcutaneous injection (daily for 18 days) or constant infusions (for 3, 9 or 18 days) and endogenous prolactin secretion was altered by exposing ewes to long day or short day photoperiods. Prolactin administration started a week after mating (in autumn), or in non pregnant ewes in mid-spring. Blood samples were collected for measurement of circulating prolactin by radioimmunoassay, skin biopsies were collected for the quantification of PRLR long (PRLR-L) and PRLR short form (PRLR-S) mRNA expression using real-time PCR assay. Wool patch samples were clipped monthly for assessing wool growth. Constant prolactin infusion of more than 3 days activated a positive feedback mechanism for PRLR-L synthesis, resulting in a sustained elevation PRLR-L mRNA expression for up to 38 days after infusion was over. This was associated with short- and long-term stimulation of wool growth in the pregnant Romney ewe. The main increase in wool production happened after parturition. This positive effect on wool growth by prolactin treatment was related to the length of prolactin treatment. A 3 day infusion resulted in a smaller degree of enhancement compared to the 9 days and 18 days. The biggest impact on wool growth was observed in one of the 18 days infused group, which resulted in a 25% increase in clean fibre production when compared to the pregnant group. The expression of PRLR-S mRNA was not associated with an elevation of prolactin levels. Daily injections neither increased PRLR-L mRNA expression nor increased wool growth, demonstrating that a constant and moderate increase in prolactin levels is necessary to stimulate PRLR synthesis. Data obtained in these trials also suggests that other reproductive hormones may influence PRLR expression and wool growth. The non-pregnant groups showed steady levels of PRLR-L mRNA expression, which could be associated with changes in hormonal levels due to the reproductive cycle. Seasonal molecules could also interfere with the system, as prolactin manipulation in non-pregnant ewes exposed to an artificial short day environment during spring time showed a different pattern of PRLR-L and PRLR-S mRNA expression and no wool growth effect. A mathematical model of prolactin/PRLR interaction was shown to be a good predictor of short-term PRLR gene expression, as its simulations agreed with our biological data. However, the inclusion of other gestational and seasonal hormones may be necessary if the model is to be used for simulations of long-term PRLR expression and wool growth during pregnancy and lactation. Overall, these results suggest that seasonal wool growth can be manipulated via prolactin, which increases PRLR-L mRNA expression resulting in enhancement of wool growth. However, there is a minimum period of constant prolactin elevation necessary to activate this positive feedback mechanism, Also there is a window of opportunity where this mechanism can be manipulated. This window is most likely associated with the animals interpretation of photoperiod, which also regulates the reproductive seasonality and therefore, could as well interact with prolactin in the regulation of PRLR mRNA expression and seasonal wool growth. This observation could lead to the development of products, suitable for on farm conditions, to enhance wool production.
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    A 0.8 fructose:maltodextrin ratio enhances endurance performance and exogenous carbohydrate oxidation : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Exercise and Sport Science at Massey University, Wellington, New Zealand
    (Massey University, 2011) O'Brien, Wendy Jean
    Introduction: A ratio of fructose to glucose/maltodextrin of approximately 0.8 in a carbohydrateelectrolyte solution ingested during endurance exercise was recently seen to substantially increase exogenous-carbohydrate oxidation, gut comfort and performance. However, it remains to be determined if the apparent fructose:glucose ratio optima is robust when the possible confounders of differences in solution osmolality and carbohydrate concentration are removed from consideration via clamping, and if the 0.8 ratio also promotes faster fluid absorption. Methods: In a randomised double-blind crossover, 12 male cyclists rode 2 h at 57.5% peak power, then performed 10 repeated-maximal-sprints, while ingesting artificially sweetened water or one of three isomotic 11.25% carbohydrate-salt solutions at 800 mL·h-1, comprising fructose and, maltodextrin/glucose, at the respective mean rates (g·min-1): 1.0, 0.5 (0.5-Ratio); 0.67, 0.83 (0.8- Ratio); 0.83, 0.67 (1.25-Ratio). Each solution was also spiked with 5 g D2O at 30 min into the 2-h preload. 14C-enriched fructose and naturally 13C-enriched maltodextrin/glucose permitted fructose and glucose oxidation rate evaluation by liquid scintillation and mass spectrometry, respectively, and indirect calorimetry. Results: Mean exogenous-fructose and mean exogenous-glucose oxidation rates were 0.27 (SD%, 46), 0.39 (56) and 0.46 g·min-1 (53), and 0.65 (30), 0.71(14) and 0.58 (28) g·min-1 in 0.5-, 0.8- and 1.25-Ratio, respectively; representing oxidation efficiencies (%) for fructose of 56 (12), 60 (7) and 56 (10), for glucose of 67 (16), 86 (11) and 89 (21), and for total exogenous-carbohydrate of 70 (9), 74 (6) and 64 (9), respectively. Relative to 0.5- and 1.25-Ratios, total exogenous-carbohydrate oxidation rate with 0.8-Ratio was very likely 6.4% (90% confidence limits; ±3.1%) and almost certainly 12.7% (±2.6%) higher, respectively, while respective differences in total-exogenous carbohydrate oxidation efficiency was 4.1±1.8% and 8.8 ±1.9%. Endogenous-carbohydrate oxidation with 1.25-Ratio was very likely higher relative to 0.5- and 0.8-Ratio conditions (31.3%; ±26.6% and 37.3%; ±27.8%, respectively) but comparisons of fat and total-carbohydrate oxidation rates were unclear among carbohydrate solutions. Mean sprint power with 0.8-Ratio was moderately higher than 0.5-Ratio (2.9%; 99% confidence limits ±2.8%) and 1.25-Ratio (3.1%; ±2.7%), and almost certainly higher than Water (11.9%; ±3.0%); repeated-sprint fatigue (slope) was possibly attenuated with 0.8-Ratio compared to 0.5- and 1.25-Ratio (2.1%; ±5.7% and 1.7%; ±5.5%, respectively). Blood D2O enrichment differences were possibly small or inconclusive among all solutions. Differences in gastrointestinal comfort during the 2-h ride were trivial/unclear among the carbohydrate conditions, however, increases in abdominal cramping were likely greater with 0.8-Ratio during the performance test. CHO ratio on CHO metabolism and performance Conclusions: Substantial enhancement of endurance performance results from ingestion of 0.8 ratio fructose:maltodextrin/glucose solutions, which is associated with increased exogenous-carbohydrate oxidation efficiency driven largely by a greater contribution from exogenous-fructose oxidation. Further research is required to determine the effect on fluid absorption and the physiological site responsible for the 0.8 ratio effect.
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    The physiological costs of wearing respiratory protective devices : a thesis in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1995) Laird, Ian Stewart; Laird, Ian Stewart
    This thesis is concerned with the use of respiratory protective devices in New Zealand industry and the physiological costs the respirator imposes on the wearer. Two cross sectional surveys of respirator users were undertaken to determine the extent and nature of use or non-use in the working environment and which factors contribute most to non-use. Evidence is presented that indicated that non-use is common (50% of those surveyed) and that difficulty breathing, thermal discomfort and difficulty communicating and seeing were all important reasons for non-use. In addition, it was found that respirators are worn for extended lengths of time and that many users believe that their work when wearing a respirator was physically demanding. Evidence is presented that this is not the case. The physical characteristics of respiratory protection in terms of resistance to airflow, weights and dead space volumes, were measured in a selection of commonly used respirators in NZ industry. It was evident that most pressure-flow relationships were below recommended limits for inspiratory and expiratory resistances and that some masks in particular, offered little external resistance to breathing. The physiological consequences of wearing respirators was examined in a series of studies measuring relationships in heart rate, oxygen consumption, ventilation, facial skin temperatures and perceived exertion, with and with-out subjects wearing respirators and at differing levels of external work. It was found that the respirator imposed little physiological strain (in terms of heart rate, gas exchange and minute ventilation), but that psycho-physiological sensations (perceived difficulty breathing and rated perceived exertion) increased significantly. In addition, increases in facial skin temperatures, particularly the lip temperature under the mask when worn, caused a sensation of thermal discomfort that may be the predominant cue that influences reasons for non-use. Finally, the incongruence between physiological and psychophysiological measures of distress was clearly demonstrated in this thesis. It is apparent that not only is a respirator a complex device, but the micro-climate it produces on the skin surface and the effect this has on an individuals' perception of discomfort, is also enigmatic.
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    The role of selenium in grazing ruminants : a thesis presented in partial fulfilment of the requirement for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1995) Wichtel, Jeffrey Jay
    Selenium (Se) deficiency has been recognised for over 30 years as a factor which limits production in grazing livestock. Diseases associated with selenium deficiency in New Zealand include nutritional myodegeneration (white muscle disease) of lambs,calves and goats, infertility of ewes and ill-thrift of sheep and cattle. Although white muscle disease is the most recognisable manifestation of deficiency, sub-clinical deficiencies are more common. Such deficiencies result in decreased growth rate, milk production and lambing percentage (Grace, 1994). The wide distribution of soils that are deficient in selenium (Watkinson, 1983) means that Se deficiency and its amelioration has considerable economic importance to New Zealand. Also of importance is lost revenue due to inappropriate supplementation leading to unnecessary expense and, on occasion, losses due to toxicity. There is a need to avoid excessive treatment to minimise the risk of selenium concentrations in ruminant liver and kidney tissue exceeding the acceptable concentration for human consumption. The development of reference ranges for the prevention of ill-thrift and myodegeneration in young stock has been the primary aim of selenium research in New Zealand to date. This has left many other aspects of selenium and its role in grazing ruminants to be elucidated. For example, there are few data on which to base reference ranges for adult dairy cattle. This lack of information was an important impetus for the studies presented in this thesis.
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    The effect of mouth rinse and ingestion of carbohydrate solution on short intensive exercise : how can we explain the increase in exercise performance? : a thesis presented for a degree of Master of Science in Sport and Exercise Science at Massey University, Auckland, New Zealand
    (Massey University, 2011) Moss, Catherine
    Background: Ingestion of carbohydrates during exercise in a fasted state has been shown to improve high-intensity exercise performance. The mechanism responsible for the improvement remains uncertain. Recent studies suggest that rinsing the mouth with a carbohydrate solution improves performance in the latter stages of high-intensity exercise without changes in circulating glucose levels. There has also been an absence of a peripheral metabolic action of exogenous carbohydrates and thus central effects have been postulated to explain this phenomenon. Aim: The purpose of the present study was to investigate whether there were individual and/or additive effects of carbohydrate mouth rinse, fluid intake and carbohydrate ingestion on 1-h time trial cycling performance. The project further investigated the response in circulating markers of fuel utilization. Methods: Eight recreationally trained cyclists volunteered for this randomised, counterbalanced, double-blind study. After a preliminary familiarisation session, four main trials were performed on an electronically-braked cycle-ergometer with each trial separated by 7 days. Each main trial took place over two days. On Day 1 the participants underwent a 90 min glycogen reducing exercise protocol, immediately followed by a low carbohydrate meal and then a subsequent overnight fast. The following morning a 1-h time trial performance test was conducted. Subjects performed a certain amount of work as fast as possible for the performance test. The main trials included a 15% carbohydrate mouth rinse (CHOR), ingestion of a 7.5% carbohydrate solution (CHOI), a placebo mouth rinse (PLAR) and placebo ingestion (PLAI); solutions were administered every 12.5% of exercise completed. Blood samples and perceptual measures (perceived activation, pleasure-displeasure and ratings of perceived exertion) were taken every 25% of exercise. A profile of mood states questionnaire was also administered prior to the time trial and immediately post exercise. Results: There were no significant differences in performance time between treatments (P=0.55). However, there was a main effect of treatment for power output (P=0.002) with higher values in CHOI (231.4 ±9.8 W) relative to other trials (222.1-224.6 W; P<0.05). Plasma glucose was higher in CHOI at 75% (5.4 mmol∙L-1) and 100% (5.9 mmol∙L-1) of the time trial relative to other trials (3.9-4.7 mmol∙L-1; P<0.05). There was a main effect of treatment for insulin (P=0.001) with highest values in CHOI (5.14 mmol∙L-1) relative to the other trials (4.2-4.7 mmol∙L-1; P<0.05). There were no significant differences reported between treatments for any of the perceptual measures. Conclusion: Ingestion of a carbohydrate-electrolyte solution was associated with a decrease in performance time during a 60-min cycling performance time trial in comparison with CHOR, PLAR and PLAI in a glycogen reduced state. This suggests that peripheral and not central effects are largely influenced by the use of a carbohydrate supplement. Keywords: fatigue, endurance performance, ergogenic, supplementation, central, peripheral, metabolism, fluid intake
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    Human behavioral temperature regulation : an exercise approach : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy (Ph.D.), School of Sport and Exercise, Massey University, Palmerston North, New Zealand
    (Massey University, 2011) Schlader, Zachary J.
    Behavior represents our most preferred and effective modality by which body temperature is regulated. However, knowledge concerning the control of this behavior in humans is relatively limited. Therefore, the overall purpose of this thesis was to further our understanding of the control of human thermoregulatory behavior. This was accomplished by firstly establishing self-paced exercise and heat stress as a thermal behavioral model, while secondly the control of this behavior was investigated. In the first part of this thesis, voluntary reductions in exercise intensity have been found to be associated with thermal discomfort and reductions in heat production, which presumably improved heat exchange between the body and the environment over time, and ultimately aided body temperature regulation. Thus, these experimental data associatively indicate that reductions in exercise intensity in the heat are thermoregulatory behaviors, suggesting that self-paced exercise in the heat is a valid model by which to evaluate human thermal behavior. The studies presented in the second part of this thesis systematically evaluated the control of this behavior. It was subsequently demonstrated that skin temperature and the accompanying alterations in thermal perception and the percentage of peak oxygen uptake elicited by a given exercise intensity are all modulators of exercise intensity, and thus thermal behavior, in the heat. Notably, reductions in peak oxygen uptake appear to play a minimal role. Importantly, these studies strengthened the associations observed in the first part of this thesis by specifically establishing a causative relationship between exercise intensity and temperature regulation. Furthermore, the experimental observations also indicated that thermal behavior during self-paced exercise is ultimately initiated by the perception of effort response. In conclusion, the findings presented in this thesis suggest that a voluntary reduction in exercise intensity occurring in the heat is a thermoregulatory behavior, and that this behavior can be directly elicited by changes associated with elevations in skin temperature. During such instances, thermal perception and the percentage of peak oxygen uptake elicited by a given exercise intensity have been uniquely identified as contributors to this behavior. The findings of this thesis improve our understanding of the control of human thermoregulatory behavior.
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    Effects of ethanol on glycogen metabolism : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biochemistry at Massey University
    (Massey University, 1997) Jeyarathan, Pooranalingam
    The effects of alcohol on glycogen structure and metabolism in fed, starved and starved-refed animals were studied in rats, taking into account factors such as post mortem degradation, careful isolation (native glycogen), and the separate structures and metabolism of low (cytosolic) and high (lysosomal) molecular weight glycogen. These studies were performed using the technique of density gradient ultracentrifugation. In fed animals, rats were administered doses of ethanol (intragastically) of either 2, 4, or 6 g/kg. The glycogen decreasing effect of ethanol was dose dependent. The lowest ethanol dose (2 g/kg) depleted liver glycogen content by 7-27%, while the highest dose (6 g/kg) showed 60-78% depletion. Ethanol doses of 4 g/kg and 6 g/kg decreased both low and high molecular weight glycogen almost evenly. There was slightly more low molecular weight glycogen loss than high with a 2 g/kg ethanol dose. In time course experiments, maximal glycogen depletion was observed at 90 minutes after an ethanol dose of 6 g/kg. After 24 hours, over-production of glycogen content was seen in ethanol treated rats. However, after 48 hours, liver glycogen content had returned to fed values in ethanol treated rats, although the content of low molecular weight glycogen was elevated relative to high molecular weight. Starvation of rats for 48 hours decreased both body weight and liver weight. The hepatic and skeletal muscle glycogen concentrations were decreased by 95% and 55% respectively. The livers of rats starved for 72 hours contained more liver glycogen than those starved for 24 hours and 48 hours. Ethanol accelerated glycogen degradation in the fed-to-starved transition. After 3 hours starvation, liver glycogen content had decreased to about half of the fed levels in ethanol treated rats. However, at 24 hours, glycogen content increased in the ethanol treated rats, to as much as twice that in the control animals. The rate and extent of depletion was greater in LMW glycogen than HMW glycogen at 6 hours and 12 hours. Studies on the effects of ethanol on the starved-to-refed transition were undertaken using two different protocols, chow refeeding and glucose administration by intragastric intubation. On chow refeeding after 48 hours starvation, liver glycogen repletion at 5 hours was decreased by about 30% in animals treated with ethanol dose of 4 g/kg. At longer time intervals there was no significant inhibition of glycogen resynthesis. The Inhibition of glycogen resynthesis at 5 hours was probably due both to a decrease in food intake in the treated animals and to inhibition of glycogen synthesis by ethanol. The rate and extent of resynthesis of high molecular weight glycogen was slower in treated rats than in control rats indicating that ethanol might preferentially inhibit the synthesis of high molecular weight glycogen, possibly through disruption or prevention of formation of disulphide bonds in the protein component of high molecular weight glycogen. Unlike liver, intragastric administration of 4 g/kg ethanol before chow refeeding following 48 hours starvation decreased muscle glycogen repletion until 24 hours refeeding, compared to the respective control rats. A single dose of intragastric administration of ethanol (3.45 g/kg) 1 hour before glucose refeeding by intragastric intubation decreased liver glycogen resynthesis by between 20-40% during the 2 hours after glucose administration. Ethanol probably delayed the peak reached in liver glycogen content by either decreasing glucose absorption, by inhibiting gluconeogenesis or glycogen synthesis, or a combination of all these factors. The overall effect of ethanol in inhibiting glycogen synthesis was not, however, nearly as great as that reported previously in similar experiments. In experiments where rats were given repeated doses of ethanol for 7 days, liver glycogen content was as much as 25 % higher in treated animals than in control animals at 24 and 48 hours after the last ethanol dose. Both low and high molecular weight glycogen had increased almost uniformly at 48 hours in the ethanol treated rats. Ethanol treatment had, however, decreased kidney glycogen content by 6-26% in the treated rats compared with the control rats, but the content of heart and muscle glycogen was not changed. The results of this research show that ethanol-induced overproduction of glycogen was seen in fed, fed-starved and starved-refed animals and also in repeated dose experiments. This finding is potentially of great importance in exercise physiology and sports science, in helping to develop recommendations for alcohol intake during training regimes.
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    The physiological and molecular response to repeated sprints in male and female team-sport athletes : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Sport and Exercise Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2009) Dent, Jessica
    Background: Due to the unique demands of the sport, athletes playing football perform a variety of differing training methods to improve physiological performance. These include strength, endurance and sprint training. While the effects of strength and endurance training have been well researched, the effects of repeated-sprint training on blood and muscle variables in well trained males and females are not well known. An understanding of changes to the blood and muscle during and following an exercise bout are important, so to gain an understanding of the type of stress and resulting adaptations that may occur. Also, while a large volume of research in training adaptations has been performed on males; little has been done on females. To date, some research indicates metabolism during moderateintensity exercise may differ between males and females; however, no study has compared repeated-sprint exercise. Therefore, it is unclear as to whether males and females would have a differing physiological response to repeated-sprint training. Purpose: The purpose of this study was to determine the effects of a repeated-sprint bout on molecular signalling in muscle and blood measures and heart rate in well-trained footballers. Additionally, we compared running times and sprint decrement (%). Research Design: Eight female senior University football players (Mean ± SD, age, 19 ± 1 y, VO ? 2peak 53.0 ± 5.1 ml·kg-1min-1) and seven male senior University football players (Mean ± SD, age, 19 ± 3 y, VO ? 2peak 59.0 ± 6.6 ml·kg-1min-1) volunteered to participate in this study. Participants performed four bouts of 6 x 30 m maximal sprints spread equally over a 40 min period. Sprint time was measured (at 30 m) for each sprint and sprint decrement was also calculated for all bouts. Muscle biopsies were taken from the vastus lateralis muscle at rest, 15 min following exercise and 2 h into recovery. Venous blood samples were taken at the same time points as the biopsies while capillary blood lactate was measured at rest and 3 min following each sprint bout. Repeated measures ANOVA and Post hoc t-tests were performed to determine significant differences between the two groups (male vs. female) and time points. Findings: Both groups had a significant (P<0.05) increase in blood lactate (mM) after the first bout of repeated sprints, with no differences between females (pre 0.9 ± 0.4 mM – post 10.0 ± 1.6 mM) and males (pre 0.8 ± 0.3 mM – post 10.0 ± 3.5 mM). Blood lactate remained elevated compared to rest (P<0.05) following bouts 2, 3 and 4 for both females (12.0 ± 3.6, 12.0 ± 3.3, 12.2 ± 3.8 mM respectively) and males (11.9 ± 2.9, 11.6 ± 2.3, 11.5 ± 4.0 mM respectively), with no differences between groups or time points (P>0.05). There were no differences (P>0.05) between the female and male athletes in mean heart rate attained at the end of each bout of repeated sprints (187 ± 2 v 190 ± 2 bpm respectively) or during recovery between sprints (140 ± 2 v 130 ± 2 bpm respectively). There were no differences between groups or time points in blood insulin (P>0.05). Fastest 30 m sprint time and mean 30 m sprint time during the repeated-sprint bout was faster for the males than females (4.58 ± 0.12 v 5.26 ± 0.27 s respectively; (P>0.05)). However, there were no differences in running velocity during the sprints between the males and females (165 ± 0.4 % vs. 155 ± 0.05 %; P>0.05) when expressed relative to velocity at VO ? 2peak (vVO ? 2peak). Also, mean % decrement during the repeated-sprint bout was lower in the males then females (4.9 ± 1.3 v 7.1 ± 1.9 % respectively; P<0.05). No changes were observed in total or phosphorylated Akt at any time-point or between genders. However, while total 4E-BP1 was lower, the ratio of total to phosphoryalated 4E-BP1 at rest was greater in males than females (P<0.05). Finally, there was also a significant decrease in 4E-BP1 phosphorylation post-exercise in males (P<0.05), but not females. Conclusions: There were no sex differences in blood lactate or heart rate throughout the repeated-sprint bout. These findings suggest that there were no cardio respiratory or lactate production/clearance differences in the response to a repeated-sprint-training bout between sexes. However, while males were faster than their female counterparts, the average relative speed was similar between sexes, suggesting a similar relative volume of work was performed during the sprint bouts. However, the females did have a greater decrement in sprint performance indicating a greater ability to recover sprint performance in the males. Sex differences in resting total and phosphorylated 4E-BP1 may indicate greater potential for muscle growth in the male athletes during basal conditions. However, differences could be due to factors other than sex, including previous training history. There was a lack of change in plasma insulin or Akt, but, similar to resistance exercise, a significant decrease in post-exercise 4E-BP1 phosphorylation for the males, but not females. The sex differences in the 4E-BP1 phosphorylation response post-exercise could be due to differences in the metabolic disturbance in the muscle during and following maximal sprints. Keywords: blood lactate, heart rate, muscle