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Subject: search.filters.subject.Athletes -- Nutrition

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    The physiological effects of nutritional thiol supplementation : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Sport and Exercise Science at Massey University, Manawatu, New Zealand
    (Massey University, 2018) McLeay, Yanita Dawn
    Endogenous antioxidant defence systems are largely comprised of thiol antioxidants and antioxidant enzymes. Keratin protein, being high in cysteic acid, has potential to improve antioxidant status via generation of several thiol antioxidants. Common dietary antioxidants are often used by athletes aiming to reduce oxidative stress, which in turn can improve exercise performance. However, whilst studies into their action against oxidative stress are positive, the subsequent effect on exercise performance is less so. In addition to having little effect on acute performance, their non-­‐specific ROS-­‐targeting mechanisms may also blunt important adaptation signalling pathways. It has been proposed that improving endogenous defence systems may be of greater benefit to athletic performance, thus keratin may be an alternative to dietary antioxidant supplementation. The first study within this thesis found acute keratin supplementation to improve plasma total thiol content, while longer term supplementation increased lean body mass significantly more than casein protein. Study two suggested one week of keratin vs. taurine supplementation did not affect plasma total thiol content, while study three found that despite no significant effects on serum total thiol content, taurine improved muscle recovery following eccentric-­‐induced muscle damage compared to a placebo. In summary, findings from this thesis suggest keratin may be a useful supplement for athletes wanting to maintain or gain lean body mass. This suggests implications for the use of keratin beyond athletes, potentially benefiting other population groups including the elderly and the sick. Results also suggest that supplementing with taurine following resistance exercise involving eccentric actions may improve recovery and subsequent performance. This research sets a platform for further investigation into the use of keratin and thiols for various areas of sporting performance.
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    [Beta]-hydroxy-[beta]-methylbutyrate (HMB) supplementation of resistance trained men : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Nutritional Science at Massey University
    (Massey University, 2004) Thomson, Jasmine Sarah
    A randomised double-blind placebo controlled study design was used to investigate the effects of supplementing 34 resistance trained men (RTM) with 3g/d of β-hydroxy-β-methylbutyrate or a cornstarch placebo on strength and body composition over a 9 week supplementation period. At the beginning of the study period, questionnaires were given to each participant. Prior to and following the period of supplementation; anthropometric measurements were taken, including 8 skinfold sites, height, and body weight; body composition was measured using bioelectrical impedance analysis: strength was assessed using 1 repetition maximum (1RM) strength testing on the leg extension, bench press, and preacher curl apparatus; and food intakes were assessed using 3-day dietary records. During the supplementation period, all participants completed the same resistance training programme and physical activity was assessed using training log book records. Prior to the supplementation period, a significant difference was found between the two supplementation groups for initial body mass indices (BMI: HMB 26.2 ± 0.8; Placebo 22.8 ± 0.9, P=0.0I4). There was no significant difference found between the HMB and Placebo supplemented groups for any other baseline anthropometric (P>0.056). or strength measurements (P>0.583). Over the study duration there was no significant difference found in number of training sessions between the two supplemented groups (P>0.056). Following the supplementation period there was no significant change in anthropometric measurements (P>0.095). nor actual strength (P>0.086) over the study duration. However, percent change in leg extension strength increased significantly more for the HMB-supplemented group than the placebo group (LE: HMB 14.7 ± 3.69% Placebo 4.84 ± 2.8%, P=0.04l). During the supplementation period there was a significant difference found between the dietary intakes of some nutrients between the supplementation groups.The HMB group tended to consume a greater percent of energy from carbohydrates, and had a higher maltose intake. The HMB group had a lower percent of energy from fats in the diet, and consumed lower average cholesterol intake than the placebo group (P <0.047). Several study participants failed to meet the recommended dietary intakes for adult New Zealanders of certain nutrients. The average intakes of energy front carbohydrates, intakes of vitamin A, vitamin E, vitamin B6. potassium, magnesium, calcium, and selenium were low for some participants. The conclusion of this study was that there was no beneficial effect of HMB supplementation on body composition in resistance trained humans, however there was a significant increase found in leg extension strength with HMB supplementation in response to resistance exercise over the 9 week supplementation period.