• An elevation of resting metabolic rate with declining health in nonagenarians may be associated with decreased muscle mass and function in women and men, respectively.

      Kim, Sangkyu; Welsh, David A.; Ravussin, Eric; Welsch, Michael A.; Cherry, Katie E.; Myers, Leann; Jazwinski, S. Michal; Tulane University Health Sciences Center; Louisiana State University Health Sciences Center; Pennington Biomedical Research Center; et al. (Oxford University Press, 2014-06)
      Previously, we showed that FI34, a frailty index based on 34 health and function ability variables, is heritable and a reliable phenotypic indicator of healthy aging. We have now examined the relationship between major components of energy expenditure and the FI34 in participants of the Louisiana Healthy Aging Study. Resting metabolic rate was associated with FI34, even after adjustment for fat-free mass, fat mass, age, sex, thyroid hormones, and insulin-like growth factor 1 levels, in multiple regression analyses. In contrast, there was no association between total daily energy expenditure and FI34. Circulating creatine phosphokinase, a clinical marker of muscle damage, was also significantly associated with FI34. However, these associations of resting metabolic rate with FI34 were restricted to the oldest old (≥90 years) and absent in younger age groups. In oldest old men, the association of FI34 with creatine phosphokinase persisted, whereas in the oldest old women, only the association with resting metabolic rate pertained with the appearance of an effect of body size and composition. These results point toward an increasing metabolic burden for the maintenance of homeodynamics as health declines in nonagenarians, and this has implications for contraction of metabolic reserve that may potentially accelerate the path to disability.
    • 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.
    • 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.
    • 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.
    • The effect of the hyperbaric environment on heat shock protein 72 expression in vivo

      Taylor, Lee; Midgley, Adrian W.; Sandström, Marie E.; Chrismas, Bryna C.; McNaughton, Lars R. (Taylor and Francis, 2012-04)
      Heat shock protein 72 (HSP72) is expressed in response to stress and has been demonstrated to follow a diurnal expression pattern within monocytes and is sensitive to changes in core temperature. Numerous studies have shown changes in HSP72 expression within cell lines exposed to hyperbaric conditions. No studies have investigated changes in HSP72 expression in vivo. Six males participated in the study and were exposed to hyperbaric air and hyperbaric oxygen a week apart. Monocyte HSP72 was analyzed by flow cytometry at 09:00, 13:00, 17:00, 21:00 with hyperbaric oxygen or hyperbaric air breathing commencing at 15:00 for 78 min at a pressure of 2.8 ATA. HSP72 under normoxia followed the established trend; however, following the hyperbaric air or oxygen exposure a reduction in detectable HSP72 was observed at 17:00 and 21:00. No changes in core temperature were observed between 13:00 and 21:00 for any condition. The data show that HSP72 expression is impaired following hyperbaric air (HA) exposure, when compared with control or hyperbaric oxygen (HO) exposure.
    • Intermittent exercise with and without hypoxia improves insulin sensitivity in individuals with type 2 diabetes

      Mackenzie, Richard W.; Maxwell, Neil S.; Castle, Paul C.; Elliott, B.; Brickley, Gary; Watt, Peter; University of Westminster (2012-04)
      Hypoxia and muscle contraction stimulate glucose transport activity in vitro. Exercise and hypoxia have additive effects on insulin sensitivity in type 2 diabetics (T2D).
    • 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.
    • Deception of ambient and body core temperature improves self paced cycling in hot, humid conditions

      Castle, Paul C.; Maxwell, Neil S.; Allchorn, Alan; Mauger, Alexis R.; White, Danny K.; University of Bedfordshire (2012-01)
      We used incorrect visual feedback of ambient and core temperature in the heat to test the hypothesis that deception would alleviate the decrement in cycling performance compared to a no deception trial. Seven males completed three 30 min cycling time trials in a randomised order on a Kingcycle ergometer. One time trial was in temperate, control conditions (CON: 21.8 ± 0.6°C; 43.3 ± 4.3%rh), the others in hot, humid conditions (HOT: 31.4 ± 0.3°C; 63.9 ± 4.5%rh). In one of the hot, humid conditions (31.6 ± 0.5°C; 65.4 ± 4.3%rh), participants were deceived (DEC) into thinking the ambient conditions were 26.0°C; 60.0%rh and their core temperature was 0.3°C lower than it really was. Compared to CON (16.63 ± 2.43 km) distance covered was lower in HOT (15.88 ± 2.75 km; P < 0.05), but DEC ameliorated this (16.74 ± 2.87 km; P < 0.05). Mean power output was greater in DEC (184.4 ± 60.4 W) than HOT (168.1 ± 54.1 W; P < 0.05) and no difference was observed between CON and DEC. Rectal temperature and iEMG of the vastus lateralis were not different, but RPE in the third minute was lower in DEC than HOT (P < 0.05). Deception improved performance in the heat by creating a lower RPE, evidence of a subtle mismatch between the subconscious expectation and conscious perception of the task demands.
    • 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.
    • 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.
    • Acute effect of fatmax exercise on the metabolism in overweight and nonoverweight girls

      Zakrzewski-Fruer, Julia K.; Tolfrey, Keith (Lippincott, Williams & Wilkins, 2012)
      Acute exercise can reduce postprandial insulin concentrations and increase fat oxidation in adults, which may have important implications for insulin resistance and weight control. However, similar studies with young people or comparing overweight (OW) and nonoverweight (NO) individuals are sparse. Therefore, the acute effect of Fatmax exercise on glucose, insulin, and fat oxidation was examined in 12 OW and 15 NO girls.
    • 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)
    • 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.
    • 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.
    • Pre-exercise alkalosis attenuates the heat shock protein 72 response to a single-bout of anaerobic exercise

      Peart, Daniel J.; McNaughton, Lars R.; Midgley, Adrian W.; Taylor, Lee; Towlson, Christopher; Madden, Leigh A.; Vince, Rebecca V. (Elsevier, 2011-09)
      The heat shock protein 72 (HSP72) response following exercise is well documented, however, little is known on whether the expression may be mediated by the ingestion of ergogenic aids prior to performance. The purpose of this research was to investigate the effect of sodium bicarbonate (NaHCO(3)) ingestion on monocyte and lymphocyte expressed HSP72 and oxidative stress for 4-h post exercise. Seven active males (22.3 ± 2.9 years, 181.6 ± 4.5 cm, 78.1 ± 8.1 kg) performed a 4-min 'all-out' cycle test following a dose of 0.3 g kg(-1) body mass of NaHCO(3), or an equimolar placebo dose of sodium chloride. HSP72 was measured by flow cytometry and oxidative stress was determined via plasma thiobarbituric acid substances (TBARS) analysis. The NaHCO(3) ingestion significantly increased blood pH (p<0.001), bicarbonate (p<0.001) and base excess (p<0.001) pre-exercise. Despite this there was no evidence of a significantly improved exercise performance when compared with the placebo trials (p ≥ 0.26) (means ± SD; average power 292 ± 43 W vs. 291 ± 50 W; peak power 770 ± 218 W vs. 775 ± 211 W; work completed 71 ± 10 kJ vs. 68 ± 10 kJ). Monocyte expressed HSP72 was significantly lower under experimental conditions during the 4-h post-exercise (p=0.013), as was plasma TBARS (p<0.001). These findings suggest that pre-exercise alkalosis can attenuate the stress response to a single bout of anaerobic exercise.
    • Exercise protocols to estimate Fatmax and maximal fat oxidation in children

      Zakrzewski-Fruer, Julia K.; Tolfrey, Keith (Human Kinetics, 2011-02)
      Consensus on the exercise protocol used to measure Fatmax (exercise intensity corresponding to maximum fat oxidation (MFO)) in children has not been reached. The present study compared Fatmax estimated using the 3 min incremental cycling protocol (3-INC) and a protocol consisting of several 10 min constant work rate exercise bouts (10-CWR) in 26 prepubertal children. Group Fatmax values were the same for 3-INC and 10-CWR (55% VO2peak) and 95% limits of agreement (LoA) were ± 7% VO2peak. Group MFO values were similar between protocols, although 95% LoA were -94 to 113 mg·min-1. While 3-INC provides a valid estimation of Fatmax compared with 10-CWR, caution should be exercised when estimating MFO in prepubertal children.
    • 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.
    • Comparison of fat oxidation over a range of intensities during treadmill and cycling exercise in children

      Zakrzewski-Fruer, Julia K.; Tolfrey, Keith (Springer, 2011)
      Substrate metabolism differs between children and adults and is important for weight management during childhood. A direct comparison of fat oxidation over a range of exercise intensities and the estimation of Fatmax (exercise intensity that elicits maximal fat oxidation (MFO)) during treadmill (TM) and cycling exercise (CE) does not appear to be available in children. Fat oxidation and Fatmax were compared during TM and CE in 22 pre- to early pubertal children (9 girls and 13 boys). Fat oxidation was higher for TM compared with CE over a range of absolute and relative exercise intensities and this difference was more pronounced at higher intensities (P ≤ 0.05). Fat oxidation was higher in boys compared with girls at similar relative, but not absolute intensities (P ≤ 0.05). Fatmax was higher during TM compared with CE and higher in boys compared with girls (P ≤ 0.05). The 5% Fatmax zone (range of exercise intensities where fat oxidation was within 5% of MFO) spanned a wider range of intensities for TM compared with CE (P ≤ 0.05). Collectively, these findings suggest that exercise programmes aimed at promoting high rates of fat oxidation in pre- to early pubertal children should include TM rather than CE regardless of exercise intensity. Furthermore, Fatmax values indicate that brisk walking or slow running promotes MFO rates in this population.
    • 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.