• Acute antioxidant pre-treatment attenuates endothelial microparticle release after decompression

      Chrismas, Bryna C.; Midgley, Adrian W.; Taylor, Lee; Vince, Rebecca V.; Laden, Gerard; Madden, Leigh A. (South Pacific Underwater Medicine Society (SPUMS), 2010-12)
      The hyperbaric and hyperoxic effects of a dive have been demonstrated to elicit changes in oxidative stress, endothelial function and microparticle (MP) release. Endothelial MP, which are small membrane vesicles shed from the endothelium, have been suggested as a valid in vivo marker of endothelial function. Furthermore, recent research has shown an increase in CD105 MP post-dive to be associated with a decline in endothelial function. The aim of this study was to ascertain whether antioxidant (AOX) pre-treatment can attenuate increased CD105 MP release post-dive.
    • 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.
    • Acute hypoxia and exercise improve insulin sensitivity (SI2*) in individuals with type 2 diabetes

      Mackenzie, Richard W.; Maxwell, Neil S.; Castle, Paul C.; Brickley, Gary; Watt, Peter (2011)
    • 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.
    • 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.
    • 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)
    • 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.
    • 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.
    • Daily quadratic trend in basal monocyte expressed HSP72 in healthy human subjects

      Taylor, Lee; Midgley, Adrian W.; Chrismas, Bryna C.; Madden, Leigh A; Vince, Rebecca V.; McNaughton, Lars R.; University of Hull (Springer, 2010-05)
      The inducible human stress protein heat shock protein 72 (HSP72) performs vital roles within the body at rest and during periods of stress. Recently it was shown over a 24 hour period that basal HSP72 followed a diurnal variation. However, these results and previous literature demonstrate noticeable inter-subject variation in basal HSP72 expression. The notion of intra/inter-day variation in basal HSP72 expression has not been explored in detail. Basal monocyte expressed HSP72 was determined every 3 hours, over a 9 hour period in 12 healthy male subjects (20.2 +/- 1.9 years, 178.7 +/- 5.6 cm, 75.1 +/- 6.0 kg) within a temperature controlled laboratory. A significant quadratic trend was observed for time (F = 26.0, P = 0.001, partial eta(2) = 0.74), where HSP72 decreased between 0800 and 1100 hours (P < 0.001) and then increased between 1100 and 1400 hours (P = 0.015). The main effect for day (F = 2.6, P = 0.14) and the day x time interaction effect (F = 3.9, P = 0.08) were not significant. There was no correlation between serum and monocyte expressed HSP72, with no significant effect for time (F = 2.0, P = 0.21) in serum HSP72 expression. The results support findings by others that basal monocyte expressed HSP72 follows a diurnal variation which incorporates a quadratic trend, which is not compromised by any significant daily variation and that serum HSP72 expression has no endogenous circadian rhythm. The significant quadratic trend in basal monocyte HSP72 expression shown here highlights the need to tightly control variables, such as timing of sample collection, as it is known basal values influence the magnitude of HSP72 expression post-stressor/intervention.
    • 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.
    • The effect of acute hypoxia on heat shock protein 72 expression and oxidative stress in vivo

      Taylor, Lee; Midgley, Adrian W.; Chrismas, Bryna C.; Madden, Leigh A.; Vince, Rebecca V.; McNaughton, Lars R. (Springer, 2010)
      The inducible human stress protein HSP72 performs vital roles within the body at rest and during periods of stress. Recently, a previously disclosed quadratic trend in basal HSP72 expression was shown to be reliable and repeatable. The notion of a physiological stressor such as hypoxia disrupting this basal quadratic trend is an interesting one. Monocyte-expressed HSP72 and TBARS were determined every 3 h, over a 12-h period in 12 healthy male subjects on two separate days, with trial day one ascertaining control values. A hypoxic intervention consisting of 75 min at a simulated altitude of 2,980 m, commencing and ceasing at 0930 and 1045, respectively, was incorporated on trail day 2. The hypoxic condition induced significantly (elevated) HSP72 values at 1100 (P = 0.002), 1400 (P < 0.001), 1700 (P = 0.034) and 2000 (P = 0.041) compared to control. Significant increases in plasma TBARS were seen in the hypoxic condition compared to control at 1100 (P = 0.006) and 1400 (P = 0.032). The results demonstrate that a 75-min bout of normobaric hypoxia is sufficient to induce significant increases in HSP72 expression, which disrupts the basal quadratic trend shown by others and here in the control condition. This increase may be linked to the observed changes in oxidative stress. These results may provide a tool for manipulating basal monocyte HSP72 expression within human heat acclimation exercise protocols.
    • Effect of breakfast glycemic index on metabolic responses during rest and exercise in overweight and non-overweight adolescent girls

      Zakrzewski-Fruer, Julia K.; Stevenson, E.J.; Tolfrey, Keith (Nature Publishing Group, 2011)
      The metabolic responses to mixed breakfast meals with different glycemic indexes (GI) and their effects on substrate metabolism during exercise in adolescent girls have not been examined. The interaction with weight status also warrants investigation. This study investigated the effect of mixed breakfast meals containing high GI (HGI) or low GI (LGI) carbohydrates on metabolic responses and fat oxidation during rest and exercise in overweight (OW) and non-overweight (NO) adolescent girls.
    • 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.
    • 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 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.
    • 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.
    • Effects of exercise intensity on salivary antimicrobial proteins and markers of stress in active men

      Allgrove, Judith E.; Gomes, Elisa; Hough, John; Gleeson, Michael; Loughborough University (Taylor & Francis, 2008-04)
      In the present study, we assessed the effects of exercise intensity on salivary immunoglobulin A (s-IgA) and salivary lysozyme (s-Lys) and examined how these responses were associated with salivary markers of adrenal activation. Using a randomized design, 10 healthy active men participated in three experimental cycling trials: 50% maximal oxygen uptake ([Vdot]O2max), 75%[Vdot]O2max, and an incremental test to exhaustion. The durations of the trials were the same as for a preliminary incremental test to exhaustion (22.3 min, s x = 0.8). Timed, unstimulated saliva samples were collected before exercise, immediately after exercise, and 1 h after exercise. In the incremental exhaustion trial, the secretion rates of both s-IgA and s-Lys were increased. An increase in s-Lys secretion rate was also observed at 75%[Vdot]O2max. No significant changes in saliva flow rate were observed in any trial. Cycling at 75%[Vdot]O2max and to exhaustion increased the secretion of α-amylase and chromogranin A immediately after exercise; higher cortisol values at 75%[Vdot]O2max and in the incremental exhaustion trial compared with 50%[Vdot]O2max were observed 1 h immediately after exercise only. These findings suggest that short-duration, high-intensity exercise increases the secretion rate of s-IgA and s-Lys despite no change in the saliva flow rate. These effects appear to be associated with changes in sympathetic activity and not the hypothalamic – pituitary – adrenal axis.
    • Effects of handgrip training with venous restriction on brachial artery vasodilation

      Credeur, Daniel P.; Hollis, Brandon C.; Welsch, Michael A.; Louisiana State University (Wolters Kluwer/ Lippincott Williams & Wilkins, 2010-07)
      Previous studies have shown that resistance training with restricted venous blood flow (Kaatsu) results in significant strength gains and muscle hypertrophy. However, few studies have examined the concurrent vascular responses following restrictive venous blood flow training protocols.