Christopher C.F. Howe
Kingston University
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Featured researches published by Christopher C.F. Howe.
Medicine and Science in Sports and Exercise | 2014
David J. Muggeridge; Christopher C.F. Howe; Owen Spendiff; Charles Pedlar; Philip E. James; Chris Easton
INTRODUCTION Increasing nitric oxide bioavailability via supplementation with nitrate-rich beetroot juice (BR) has been shown to attenuate the negative effect of hypoxia on peripheral oxygen saturation and exercise tolerance. PURPOSE We investigated the effects of a single dose of concentrated BR on the physiological responses to submaximal exercise and time trial (TT) performance in trained cyclists exposed to moderate simulated altitude (approximately 2500 m). METHODS Nine competitive amateur male cyclists (age, 28 ± 8 yr; V˙O2peak at altitude, 51.9 ± 5.8 mL·kg·min) completed four exercise trials consisting of an initial graded test to exhaustion and three performance trials on a cycle ergometer. The performance trials comprised 15 min of submaximal steady-state exercise at 60% maximum work rate and a 16.1-km TT. The second and third trials were preceded by ingestion of either 70 mL of BR or nitrate-depleted BR (PLA) 3 h before exercise. RESULTS Plasma nitrate (PLA, 39.1 ± 3.5 µM; BR, 150.5 ± 9.3 µM) and nitrite (PLA, 289.8 ± 27.9 nM; BR, 678.1 ± 103.5 nM) measured immediately before exercise were higher after ingestion of BR compared with that after PLA (P < 0.001, P = 0.004). V˙O2 during steady-state exercise was lower in the BR trial (2542 ± 114 mL·min) than that in the PLA trial (2727 ± 85 mL·min, P = 0.049). TT performance was significantly faster after BR (1664 ± 14 s) than that after PLA (1702 ± 15 s, P = 0.021). CONCLUSION A single dose of BR lowered V˙O2 during submaximal exercise and enhanced TT performance of trained cyclists in normobaric hypoxia. Consequently, ingestion of BR may be a practical and effective ergogenic aid for endurance exercise at altitude.
Journal of Sports Sciences | 2014
Christopher C.F. Howe; Richard O. Matzko; Fabio Piaser; Yannis Pitsiladis; Chris Easton
Abstract This study investigated the stability of the measurement of respiratory variables during rest, walking and running using the K4b2 portable metabolic analyser in ten active males (age 31 ± 11 years; peak 42.1 ± 2.6 ml · min−1 · kg−1). Following a 10 min rest, participants completed three discontinuous incremental exercise tests on a treadmill while walking (4, 5 and 6 km · h−1) and running (8, 10, 12, 14 and 16 km · h−1, or until volitional exhaustion). Participants completed 3 min of exercise at each speed, followed by a 3 min recovery after each stage above 10 km · h−1. The respiratory variables were measured using either a laboratory-based metabolic cart as a reference method (Oxycon Pro, OP), a K4b2 calibrated immediately before the test (K4b2), or a K4b2 calibrated 1 h before the test (K4b2DEL). Compared to the OP, carbon dioxide production () and were not different when measured by K4b2 or K4b2DEL. There was no difference in between OP and K4b2 tests (P = 0.19, mean difference = 38 ml · min−1 and limits of agreement (LOA) = 208 to –285) although K4b2DEL overestimated (P = 0.05, mean difference = 84 ml · min−1 and LOA = 302 to –469). These data suggest that a drift in measurement accuracy appears to cause the K4b2 to overestimate in tests lasting longer than 1 h.
Metabolites | 2018
Christopher C.F. Howe; Ahmed Alshehri; David J. Muggeridge; Alexander B. Mullen; Marie Boyd; Owen Spendiff; Hannah J. Moir; David G. Watson
Metabolomic profiling of nine trained ultramarathon runners completing an 80.5 km self-paced treadmill-based time trial was carried out. Plasma samples were obtained from venous whole blood, collected at rest and on completion of the distance (post-80.5 km). The samples were analyzed by using high-resolution mass spectrometry in combination with both hydrophilic interaction (HILIC) and reversed phase (RP) chromatography. The extracted putatively identified features were modeled using Simca P 14.1 software (Umetrics, Umea, Sweden). A large number of amino acids decreased post-80.5 km and fatty acid metabolism was affected with an increase in the formation of medium-chain unsaturated and partially oxidized fatty acids and conjugates of fatty acids with carnitines. A possible explanation for the complex pattern of medium-chain and oxidized fatty acids formed is that the prolonged exercise provoked the proliferation of peroxisomes. The peroxisomes may provide a readily utilizable form of energy through formation of acetyl carnitine and other acyl carnitines for export to mitochondria in the muscles; and secondly may serve to regulate the levels of oxidized metabolites of long-chain fatty acids. This is the first study to provide evidence of the metabolic profile in response to prolonged ultramarathon running using an untargeted approach. The findings provide an insight to the effects of ultramarathon running on the metabolic specificities and alterations that may demonstrate cardio-protective effects.
Measurement in Physical Education and Exercise Science | 2017
Christopher C.F. Howe; Hannah J. Moir; Chris Easton
ABSTRACT This study establishes tri-axial activity count (AC) cut-points for the GT3X+ accelerometer to classify physical activity intensity in overweight and obese adults. Further, we examined the accuracy of established and novel energy expenditure (EE) prediction equations based on AC and other metrics. Part 1: Twenty overweight or obese adults completed a 30 minute incremental treadmill walking protocol. Heart rate (HR), EE, and AC were measured using the GT3X+ accelerometer. Part 2: Ten overweight and obese adults conducted a self-paced external walk during which EE, AC, and HR were measured. Established equations (Freedson et al., 1998; Sasaki et al., 2011) overestimated EE by 40% and 31%, respectively (p < .01). Novel gender-specific prediction equations provided good estimates of EE during treadmill and outdoor walking (standard error of the estimate = .91 and .65, respectively). We propose new cut-points and prediction equations to estimate EE using the GT3X+ tri-axial accelerometer in overweight and obese adults.
British Journal of Sports Medicine | 2013
K A Zwygart; Christopher C.F. Howe; Hannah J. Moir
This study examined whether the magnitude of the effects of an exercise bout on inflammatory markers and iron regulation in humans differs between trained and untrained men. Changes in cell count (red blood cell, white blood cell, haemoglobin, haematocrit, lymphocytes, monocytes, granulocytes) Interleukin-6 (IL-6) and serum iron in response to a running bout were compared between both groups. Seven untrained (VO2max 47.4±4.1 ml·kg−1·min−1) and seven trained (56.9±4.5 ml·kg−1·min−1) men aged 19–48 years completed a Bruce protocol treadmill test and a subsequent treadmill run (45 min at 75% of VO2max). Ethical approval was granted by Kingston University Faculty Ethics Committee and conducted in accordance to the Declaration of Helsinki. Venous whole blood was collected before, and at 0, 3, 6 and 24 after exercise. Exercise-induced plasma volume changes were accounted for. Mixed Model ANOVA was performed to examine differences within groups. Independent t-tests identified which time points differed between groups, and dependent t-tests were applied to examine changes within groups over time. Significance was accepted at P<0.05. Differences between groups were observed for haemoglobin (P<0.005) and red blood cell (P=0.007) at all time points, as well as for haematocrit at all time points except at baseline (P=0.013). Lymphocytes, Monocytes, Granulocytes, IL-6 and iron levels did not differ between groups. IL-6 levels were increased post-exercise in both groups, and iron was different 3 h post-exercise to 6 h post-exercise (P<0.05). Findings suggest haemoglobin, haematocrit and red bloods to be lower in trained individuals due to adaptations of endurance training. The single exercise running bout elicited an acute inflammatory response represented by an increase in IL-6 and decrease in serum iron. Alterations in IL-6 were not different between trained and untrained men, indicating a lack of effect of training status.
International Journal of Sport Nutrition and Exercise Metabolism | 2013
David J. Muggeridge; Christopher C.F. Howe; Owen Spendiff; Charles Pedlar; Philip E. James; Chris Easton
Nitric Oxide | 2012
D.J. Muggeridge; Christopher C.F. Howe; Owen Spendiff; Charles Pedlar; Phillip James; Chris Easton
Medicine and Science in Sports and Exercise | 2012
Chris Easton; Christopher C.F. Howe; Richard O. Matzko; Fabio Piaser; Yannis Pitsiladis
Archive | 2011
Christopher C.F. Howe; Chris Easton
Archive | 2017
Ahmed Alshehri; Christopher C.F. Howe; David J. Muggeridge; Alexander B. Mullen; Marie Boyd; Owen Spendiff; Elizabeth Pummell; Hannah J. Moir; David G. Watson