Now showing items 21-40 of 46

    • Fatmax in children and adolescents: a review

      Zakrzewski-Fruer, Julia K.; Tolfrey, Keith (Taylor and Francis, 2011)
      The purpose of this review is to summarise and critically examine the literature that has determined Fatmax in children and adolescents (young people). Maximising fat oxidation during exercise may be beneficial for health, particularly in the management of metabolic diseases such as obesity and type 2 diabetes. Exercise intensity largely determines fat oxidation during exercise. Fatmax is the relative exercise intensity that elicits the highest fat oxidation rate and has received increasing attention in recent years. Studies in young people have demonstrated that there is considerable inter-individual variation in Fatmax, which generally occurs between 30 and 60% of peak oxygen uptake. Factors that may influence Fatmax in young people include body composition, physical maturation, and exercise training. Several researchers have suggested that Fatmax and fat oxidation rates may be reduced in obese compared with non-obese young people.
    • Breakfast, metabolism, health and cognitive function in young people

      Tolfrey, Keith; Zakrzewski-Fruer, Julia K.; Cooper, Simon B.; Nevill, Mary E. (Nova Publishers Inc, 2012)
    • Breakfast, glycaemic index and health in young people

      Tolfrey, Keith; Zakrzewski-Fruer, Julia K. (Elsevier, 2012)
      The purpose of this paper was to extend previous reviews on breakfast consumption and health to provide a greater understanding of the role of breakfast composition, particularly breakfast GI. Unlike the evidence on breakfast consumption, which has often been based on large cross-sectional studies, the evidence on breakfast GI is based primarily on controlled experimental studies, often with relatively small samples. At times, it was necessary to refer to the adult-based literature in this review to support findings from young people or to highlight areas that are particularly lacking in empirical evidence in this population. Since breakfast consumption has declined in young people and also decreases from childhood to adolescence, strategies to promote regular consumption of a healthy breakfast in young people are warranted. Future research in young people should place greater emphasis on breakfast composition, consider the mechanisms controlling relationships between breakfast consumption and health, and investigate the benefits of habitual consumption of LGI compared with HGI breakfasts.
    • The oxygen uptake kinetic response to moderate intensity exercise in overweight and non-overweight children

      Potter, C.R.; Zakrzewski-Fruer, Julia K.; Draper, S.B.; Unnithan, V.B. (Nature Publishing Group, 2012)
      The aim of the study was to compare the phase II oxygen uptake time constant (τV'O(2)) and V'O(2) mean response time (V'O(2)MRT) in overweight (OW) and non-OW (NO) children during moderate intensity exercise. The findings demonstrate impairment in the factors determining V'O(2) kinetics in OW children at a relatively young age. Furthermore, assessment of cardiorespiratory fitness using peak exercise values is likely to be misleading and not useful when designing exercise programmes for OW children.
    • Biomechanics of ankle instability. Part 1: reaction time to simulated ankle sprain

      Mitchell, Andrew C.S.; Dyson, Rosemary; Hale, Tudor; Abraham, Corinne (American College of Sports Medicine, 2008)
      The purpose of the study was to test the hypothesis that ankles with functional instability will demonstrate slower muscular reaction times than their contralateral stable ankle (SA) and stable healthy controls to a simulated nonpathological ankle sprain mechanism. Results demonstrate a deficit (slower reaction time) in ankles with FAI when acting in support and when exposed to a simulated sprain compared to stable healthy controls. As a result of slower reaction times, acting to support the UA may put the contralateral SA at an increased risk of ankle sprain. This suggests that rehabilitation of a lateral ankle sprain should include strengthening the evertors (peroneals and EDL) at the subtalar joint and the dorsiflexors (TA and EDL) at the talocrural joint.
    • Biomechanics of ankle instability. Part 2: postural sway-reaction time relationship

      Mitchell, Andrew C.S.; Dyson, Rosemary; Hale, Tudor; Abraham, Corinne (American College of Sports Medicine, 2008)
      The purpose of this study was to test the hypothesis that ankles with functional instability will demonstrate greater single-limb postural sway (PS) than their contralateral stable joint and stable healthy controls and to examine the relationship between single-limb postural sway and muscular reaction time to a simulated ankle sprain mechanism. Results reveal postural sway deficits in ankles with FAI. They also demonstrate a significant relationship between PL and PB reaction times and postural sway in UA. Individuals who sustain an acute ankle sprain and those with FAI require rehabilitation that improves proprioception, strengthens the evertors and dorsiflexors, and restores peroneal reaction time.
    • Foot structure and muscle reaction time to a simulated ankle sprain

      Denyer, Joanna R.; Hewitt, Naomi L. A.; Mitchell, Andrew C.S. (The National Athletic Trainers' Association, 2013)
      The study was to determine whether pronated or supinated foot structures contribute to neuromuscular deficits as measured by muscle reaction time to a simulated ankle-sprain mechanism. Conclusions: Foot structure influenced peroneus longus reaction time. Further research is required to establish the consequences of slower peroneal reaction times in pronated and supinated foot structures. Researchers investigating lower limb muscle reaction time should control for foot structure because it may influence results.
    • The effect of isokinetic testing speed on the reliability of muscle fatigue indicators during a hip abductor-adductor fatigue protocol

      Gautrey, Charlotte N.; Watson, T.; Mitchell, Andrew C.S. (Thieme Publishing, 2013)
      The aim of this study was to investigate the reliability of fatigue indicators calculated from peak torque and total work during isokinetic speeds of 60, 90, 120 and 180° · s-1 during a hip fatigue protocol.
    • The effect of velocity on load range during isokinetic hip abduction and adduction exercise

      Gautrey, Charlotte N.; Watson, T.; Mitchell, Andrew C.S. (Thieme Publishing, 2013)
      The purpose of this study was to quantify the components of acceleration, load range and deceleration through a velocity spectrum during concentric hip abduction and adduction isokinetic exercise, and to investigate the effect of load range on peak torque and work done.
    • London 2012 training guide athletics - track events

      Brewer, John (Carlton Books Ltd, 2011)
      This training book is the perfect introduction to the Olympic Athletics track events and will prove an indispensable guide for both the keen beginner and club athlete. Written by a leading sports scientist and fully illustrated with over 50 specially commissioned diagrams, this official book gives an overview of each track event and covers training safety, tactics and techniques, and standards of performance to aim for. Whether you are a beginner who simply wants to try a new sport or a budding Olympian who dreams of one day winning a gold medal, this concise and easy-to-use book will take you to the next level.
    • A multi-ingredient nutritional supplement increases fat oxidation and augments metabolic rate

      Saini, Amarjit; McBride, Roisin; Davies, Ben Rhys; Martin, Neil Richard William; Sculthorpe, Nicholas; Brewer, John (SciTechnol, 2013)
      The study investigated the impact of a multi-ingredient nutritional supplement (MINS) on resting metabolic rate and energy expenditure. The supplement contained a combination of factors that are normally administered in isolation (32 g protein, 8.4 g CHO, 1.7 g fibre, 105 mg caffeine and 21 mg green tea extract with 10.5 mg catechins, per 50 g serving. 18 subjects participated in the study (10 males, 8 females), mean age 21.8 yrs. Following overnight fasting, subjects ingested either MINS or an isocaloric maltodextrin placebo. Resting oxygen uptake was determined by gas analysis measuring VCO2 produced and VO2 consumed. 7 days later, the protocol was repeated using a randomised twotreatment crossover design so each individual subject’s response to both placebo and supplement was assessed. Results showed mean resting Respiratory Exchange Ratios were 0.77 ± 0.03 after supplementation, compared with 0.93 ± 0.03 after placebo (P<0.05), indicating a shift in contribution of fat to metabolism from 24 ± 2.5% (Control) to 79 ± 1.9% (MINS). Mean resting metabolic rate was found to be 3.69 ml per kg.min-1 O2 after supplementation, compared with 3.45 ml per kg.min-1 O2 after placebo. Whilst this difference is not statistically significant, it impacts on the absolute amount of fat metabolised at rest, increasing from 0.3 kcal.min-1 (Control) to 1.0 kcal.min-1 (MINS) (P<0.05). These findings may have significant implications for individuals involved in weight loss or weight management programmes.
    • Partial heat acclimation of athletes with spinal cord lesion

      Castle, Paul C.; Kularatne, B. Pasan; Brewer, John; Mauger, Alexis R.; Austen, Ross A.; Tuttle, James A.; Sculthorpe, Nicholas; Mackenzie, Richard W.; Maxwell, Neil S.; Webborn, Anthony D. J. (Springer, 2012)
      Heat acclimation (HA) can improve thermoregulatory stability in able-bodied athletes in part by an enhanced sweat response. Athletes with spinal cord lesion are unable to sweat below the lesion and it is unknown if they can HA. Five paralympic shooting athletes with spinal cord lesion completed seven consecutive days HA in hot conditions (33.4 ± 0.6 °C, 64.8 ± 3.7 %rh). Each HA session consisted of 20 min arm crank exercise at 50 % [Formula: see text] followed by 40 min rest, or simulated shooting. Aural temperature (T (aur)) was recorded throughout. Body mass was assessed before and after each session and a sweat collection swab was fixed to T12 of the spine. Fingertip whole blood was sampled at rest on days 1 and 7 for estimation of the change in plasma volume. Resting T (aur) declined from 36.3 ± 0.2 °C on day 1 to 36.0 ± 0.2 °C by day 6 (P < 0.05). During the HA sessions mean, T (aur) declined from 37.2 ± 0.2 °C on day 1, to 36.7 ± 0.3 °C on day 7 (P < 0.05). Plasma volume increased from day 1 by 1.5 ± 0.6 % on day 7 (P < 0.05). No sweat secretion was detected or changes in body mass observed from any participant. Repeated hyperthermia combined with limited evaporative heat loss was sufficient to increase plasma volume, probably by alterations in fluid regulatory hormones. In conclusion, we found that although no sweat response was observed, athletes with spinal cord lesion could partially HA.
    • Low calorie sweetness and hydration: applications in exercise and sport

      Brewer, John (Teknoscienze Srl, 2011)
      Loss of fluid and energy stores are key challenges faced during sport and exercise. Consumption of beverages containing optimal concentrations of fluid, energy and electrolytes are known to offer the best means of delivering fuel and energy to the body during exercise, with palatability a key factor in determining volitional fluid consumption. In certain cases, where weight loss is a primary goal for exercise, a low energy level in a beverage is of increased importance. Hence many manufacturers use low calorie sweeteners within a sports beverage to ensure that the product retains optimal scientific constituents, calorific content and palatability
    • Plasma and salivary steroid hormone responses of men to high-intensity cycling and resistance exercise

      Hough, John; Papacosta, Elena; Wraith, Elizabeth; Gleeson, Michael (Lippincott, Williams & Wilkins, 2011)
      Hormonal responses to exercise could be used as a marker of overreaching. A short exercise protocol that induces robust hormonal elevations in a normal trained state should be able to highlight hormonal changes during overreaching. This study compared plasma and salivary cortisol and testosterone responses to 4 exercise trials; these were (a) continuous cycle to fatigue at 75% peak power output (Wmax) (FAT); (b) 30-minute cycle alternating 1-minute 60% and 1 minute 90% Wmax (60/90); (c) 30-minute cycle alternating 1-minute 55% and 4-minute 80% Wmax (55/80); and (d) Squatting 8 sets of 10 repetitions at 10 repetition maximum (RESIST). Blood and saliva samples were collected pre-exercise and at 0, 10, 20, 30, 40, 50, and 60 minute postexercise. Pre- to postexercise plasma cortisol increased in all exercise trials, except 60/90. Increases in 55/80 remained above pre-exercise levels for the entire postexercise period. Salivary cortisol increased from pre- to postexercise in FAT and 55/80 trials only. Once elevated after 55/80, it remained so for the postexercise period. Plasma testosterone increased from pre- to postexercise in all trials except 55/80. Saliva testosterone increased from pre- to postexercise in all trials with the longest elevation occurring after 55/80. Area under the curve analysis indicated that the exercise response of salivary hormones was greater in all cycle trials (cortisol) and in the 60/90 and 55/80 trials (testosterone) compared with the other trials. This study indicates that the 55/80 cycle protocol induces a prolonged salivary and plasma cortisol and salivary testosterone response compared with the other trials and so may be a useful diagnostic tool of overreaching.
    • Hypoxia-mediated prior induction of monocyte-expressed HSP72 and HSP32 provides protection to the disturbances to redox balance associated with human sub-maximal aerobic exercise.

      Taylor, Lee; Hillman, Angela R.; Midgley, Adrian W.; Peart, Daniel J.; Chrismas, Bryna C.; McNaughton, Lars R.; University of Bedfordshire (2012-03-23)
      HSP72 is rapidly expressed in response to a variety of stressors in vitro and in vivo (including hypoxia). This project sought a hypoxic stimulus to elicit increases in HSP72 and HSP32 in attempts to confer protection to the sub-maximal aerobic exercise-induced disturbances to redox balance. Eight healthy recreationally active male subjects were exposed to five consecutive days of once-daily hypoxia (2,980 m, 75 min). Seven days prior to the hypoxic acclimation period, subjects performed 60 min of cycling on a cycle ergometer (exercise bout 1-EXB1), and this exercise bout was repeated 1 day post-cessation of the hypoxic period (exercise bout 2-EXB2). Blood samples were taken immediately pre- and post-exercise and 1, 4 and 8 h post-exercise for HSP72 and immediately pre, post and 1 h post-exercise for HSP32, TBARS and glutathione [reduced (GSH), oxidised (GSSG) and total (TGSH)], with additional blood samples obtained immediately pre-day 1 and post-day 5 of the hypoxic acclimation period for the same indices. Monocyte-expressed HSP32 and HSP72 were analysed by flow cytometry, with measures of oxidative stress accessed by commercially available kits. There were significant increases in HSP72 (P < 0.001), HSP32 (P = 0.03), GSSG (t = 9.5, P < 0.001) and TBARS (t = 5.6, P = 0.001) in response to the 5-day hypoxic intervention, whereas no significant changes were observed for GSH (P = 0.22) and TGSH (P = 0.25). Exercise-induced significant increases in HSP72 (P < 0.001) and HSP32 (P = 0.003) post-exercise in EXB1; this response was absent for HSP72 (P ≥ 0.79) and HSP32 (P ≥ 0.99) post-EXB2. The hypoxia-mediated increased bio-available HSP32 and HSP72 and favourable alterations in glutathione redox, prior to exercise commencing in EXB2 compared to EXB1, may acquiesce the disturbances to redox balance encountered during the second physiologically identical exercise bout.
    • Daily hypoxia increases basal monocyte HSP72 expression in healthy human subjects

      Taylor, Lee; Midgley, Adrian W.; Chrismas, Bryna C.; Hilman, Angela R.; Madden, Leigh A.; Vince, Rebecca V.; McNaughton, Lars R.; University of Bedfordshire (2011-02)
      Heat shock protein 72 (HSP72) performs vital roles within the body at rest and during periods of stress. In vitro, research demonstrates HSP72 induction in response to hypoxia. Recently, in vivo, an acute hypoxic exposure (75 min at 2,980 m) was sufficient to induce significant increases in monocyte expressed HSP72 (mHSP72) and a marker of oxidative stress in healthy human subjects. The purpose of the current study was to identify the impact of 10 consecutive days of hypoxic exposures (75 min at 2,980 m) on mHSP72 and erythropoietin (EPO) expression, markers of oxidative stress, and maximal oxygen consumption in graded incremental aerobic exercise. Eight male subjects were exposed to daily normobaric hypoxic exposures for 75 min at 2,980 m for 10 consecutive days, commencing and ceasing at 0930 and 1045, respectively. This stressor was sufficient to induce significant increases in mHSP72, which was significantly elevated from day 2 of the hypoxic exposures until 48 h post-final exposure. Notably, this increase had an initial rapid (30% day on day compared to baseline) and final slow phase (16% day on day compared to baseline) of expression. The authors postulate that 7-day hypoxic exposure in this manner would be sufficient to induce near maximum hypoxia-mediated basal mHSP72 expression. Elevated levels of mHSP72 are associated with acquired thermotolerance and provide cross tolerance to non-related stressors in vivo, the protocol used here may provide a useful tool for elevating mHSP72 in vivo. Aside from these major findings, significant transient daily elevations were seen in a marker of oxidative stress, alongside sustained increases in EPO expression. However, no physiologically significant changes were seen in maximal oxygen consumption or time to exhaustion.
    • A new VO2max protocol allowing self-pacing in maximal incremental exercise

      Mauger, Alexis R.; Sculthorpe, Nicholas; University of Bedfordshire (2012-01)
      The traditional maximal oxygen uptake (VO(2max)) protocol has received criticism for being an unnatural form of exercise, lacking ecological validity and producing different VO(2max) responses depending on protocol duration and work rate increments.
    • The effect of different dynamic stretch velocities on jump performance.

      Fletcher, Iain M.; University of Bedfordshire (2010-06)
      Dynamic stretching has gained popularity, due to a number of studies showing an increase in high intensity performance compared to static stretch modalities. Twenty-four males (age mean 21 +/- 0.3 years) performed a standardised 10 min jogging warm-up followed by either; no stretching (NS), slow dynamic stretching at 50 b/min (SDS) or fast dynamic stretching at 100 b/min (FDS). Post-warm-up, squat, countermovement and depth jumps were performed. Heart rate, tympanic temperature, electromyography (EMG) and kinematic data (100 Hz) were collected during each jump. Results indicated that the FDS condition showed significantly greater jump height in all tests compared to the SDS and NS conditions. Further, the SDS trial resulted in significantly greater performance in the drop and squat jump compared to the NS condition. The reasons behind these performance changes are multi-faceted, but appear to be related to increases in heart rate and core temperature with slow dynamic stretches, while the greater increase in performance for the fast dynamic stretch intervention is linked to greater nervous system activation, shown by significant increases in EMG. In conclusion, a faster dynamic stretch component appears to prepare an athlete for a more optimum performance.
    • An investigation into the possible physiological mechanisms associated with changes in performance related to acute responses to different preactivity stretch modalities.

      Fletcher, Iain M.; Monte-Colombo, Mathew M.; University of Bedfordshire (2010-02)
      The aim of this study was to explore the potential mechanisms underlying performance changes linked to different warm-up stretch modalities. Twenty-one male collegiate-semiprofessional soccer players (age, 20.8 +/- 2.3 years) performed under 3 different warm-up conditions: a no-stretch warm-up (WU), a warm-up including static passive stretches (SPS), and a warm-up incorporating static dynamic stretches (SDS). Countermovement jump, drop jump, peak torque, heart rate, core temperature, movement kinematics, and electromyography (EMG) were recorded for each intervention. Significant increases (p < 0.001) in performance were recorded for the countermovement, drop jump, and peak torque measures when the SDS was compared with the WU and SPS trials. When mechanism data were analysed, heart rate was significantly higher (p < 0.001) in the SDS condition compared with the SPS and WU conditions (a pattern also shown with core temperature), whereas the WU condition heart rate was also significantly higher than the SPS condition heart rate. When EMG data were examined for the rectus femoris muscle, significantly greater (p < 0.01) muscle activity was observed in the SDS condition compared with the SPS condition. It seems the most likely mechanisms to explain the increase in performance in the SDS condition compared with the SPS condition are increased heart rate, greater muscle activity, and increased peak torque.