James Bray

Sodium bicarbonate supplementation and ingestion timing: does it matter?

Abstract Siegler, JC, Marshall, PWM, Bray, J, and Towlson, C. Sodium bicarbonate supplementation and ingestion timing: Does it matter? J Strength Cond Res 26(7): 1953–1958, 2012—Although a considerable amount of literature exists on the ergogenic potential of ingesting sodium bicarbonate (NaHCO3) before short-term, high-intensity exercise, very little exists on optimal loading times before exercise. The purpose of this study was to determine the influence of NaHCO3 supplementation timing on repeated sprint ability (RSA). Eight men completed 3 (randomized and counterbalanced) trials of ten 10-second sprints separated by 50 seconds of active recovery (1:5 work-to-rest) on a nonmotorized treadmill. Before each trial, the subjects ingested 0.3 g·kg−1 body weight of NaHCO3 at 60 (H1), 120 (H2), or 180 (H3) minutes before exercise. Additionally, the subjects were assessed for any side effects (gastrointestinal [GI] discomfort) from the NaHCO3 ingestion via a visual analog scale (VAS). Blood buffering was assessed using a 2-way analysis of variance (ANOVA) with repeated measures, whereas repeated sprint performance and GI discomfort were assessed via a 1-way ANOVA with repeated measures. Blood-buffering capacity was not different at preexercise times ( [millimoles per liter] H1: 30.2 ± 0.4, H2: 30.9 ± 0.6, H3: 31.2 ± 0.6; p > 0.74). Average speed, average power, and total distance covered progressively declined over the 10 sprints; however, there was no difference between conditions (p > 0.22). The incidence of GI discomfort was significantly higher (p < 0.05) from preingestion at all time points with the exception of 180 minutes, whereas severity was only different between 90 and 180 minutes. Ingestion times (between 60 and 180 minutes) did not influence the blood buffering or the ergogenic potential of NaHCO3 as assessed by RSA. However, VAS scores indicated that at 180 minutes postingestion, an individual is less prone to experiencing significant GI discomfort.

A Comparison of Hyperhydration Versus Ad Libitum Fluid Intake Strategies on Measures of Oxidative Stress, Thermoregulation, and Performance

Dehydration has been shown to augment cellular stress. Glycerol hyperhydration can delay dehydration, which may decrease the level of pre- and post-exercise oxidative stress. This study aimed to compare the effects of glycerol (G) or water (W) hyperhydration with no hyperhydration (C) on oxidative stress, thermoregulation, and cycle performance. Seven trained males consumed 1.2 g of glycerol·kg−1 body mass (BM) in 26 ml·kg−1 BM water or equal volume water to achieve hyperhydration followed by a 90 min time trial. Total glutathione increased post exercise (PE) in all trials (p < 0.01), while oxidized glutathione (p < 0.05) and protein carbonyl concentrations (p < 0.001) were increased PE for the C trial only. Mean body temperature and heart rate increased with exercise but were not different between interventions. Total distance covered and power outputs were not different between interventions. Fluid intake attenuated oxidative stress but did not enhance thermoregulation or performance.

The validity and inter-device variability of the Apple Watch™ for measuring maximal heart rate.

ABSTRACT Maximal heart rate (HRmax) is a fundamental measure used in exercise prescription. The Apple Watch™ measures heart rate yet the validity and inter-device variability of the device for measuring HRmax are unknown. Fifteen participants completed a maximal oxygen uptake test while wearing an Apple Watch™ on each wrist. Criterion HRmax was measured using a Polar T31™ chest strap. There were good to very good correlations between the watches and criterion (left: r = 0.87 [90%CI: 0.67 to 0.95]; right: r = 0.98 [90%CI: 0.94 to 0.99]). Standardised mean bias for the left and right watches compared to the criterion were 0.14 (90%CI: −0.12 to 0.39; trivial) and 0.04 (90%CI: −0.07 to 0.15; trivial). Standardised typical error of the estimate for the left and right watches compared to the criterion were 0.51 (90%CI: 0.38 to 0.80; moderate) and 0.22 (90%CI: 0.16 to 0.34; small). Inter-device standardised typical error was 0.46 (90%CI: 0.36 to 0.68; moderate), ICC = 0.84 (90%CI: 0.65 to 0.93). The Apple Watch™ has good to very good criterion validity for measuring HRmax, with no substantial under- or over-estimation. There were moderate and small prediction errors for the left and right watches. Inter-device variability in HRmax is moderate.

Aspartame in conjunction with carbohydrate reduces insulin levels during endurance exercise.

BackgroundAs most sport drinks contain some form of non-nutritive sweetener (e.g. aspartame), and with the variation in blood glucose regulation and insulin secretion reportedly associated with aspartame, a further understanding of the effects on insulin and blood glucose regulation during exercise is warranted. Therefore, the aim of this preliminary study was to profile the insulin and blood glucose responses in healthy individuals after aspartame and carbohydrate ingestion during rest and exercise.FindingsEach participant completed four trials under the same conditions (45 min rest + 60 min self-paced intense exercise) differing only in their fluid intake: 1) carbohydrate (2% maltodextrin and 5% sucrose (C)); 2) 0.04% aspartame with 2% maltodextrin and 5% sucrose (CA)); 3) water (W); and 4) aspartame (0.04% aspartame with 2% maltodextrin (A)). Insulin levels dropped significantly for CA versus C alone (43%) between pre-exercise and 30 min, while W and A insulin levels did not differ between these time points.ConclusionsAspartame with carbohydrate significantly lowered insulin levels during exercise versus carbohydrate alone.

Effectiveness of short-term heat acclimation on intermittent exercise in thermoneutral and hot environments

It is well-established that repetition of heat stress exposure has been shown to facilitate adaptations to the heat but these protocols have tended to be of a fixed work intensity, continuous exercise, long-term in duration (>7 days) and use hydration. Secondly, there is limited information on the potential use of heat acclimation as a training method for human performance in thermoneutral conditions. Therefore, the aims of this study were to investigate the effectiveness of short-term heat acclimation (STHA) for 5 days, using the controlled hyperthermia technique with dehydration, on intermittent exercise in thermoneutral and hot environments.

Effectiveness of a six-week high-intensity interval training programme on cardiometabolic markers in sedentary males

Physical activity, sedentary lifestyles and low levels of aerobic fitness are independent risk factors in the pathogenesis of pre-diabetes and type 2 diabetes mellitus (T2DM). The school environment lends itself to seasonal periods of decreased physical activity and aerobic fitness with time constraints in physical education classes being cited as the main barrier to achieving appropriate physical activity levels. Sprint interval training (SIT) that involves short bursts of very high-intensity exercise intervals interspersed with low-intensity exercise intervals has been reported as a time efficient method of improving physical, cardiovascular and metabolic health, though research is lacking in the adolescent population. The study aimed to investigate the effects of a 7-week school-based SIT intervention on aerobic fitness and insulin sensitivity in Scottish adolescent scholars during the first semester of school following a summer vacation period. Following ethical approval from the University of the West of Scotland, 49 apparently healthy, young males and females were selected from a secondary school in the West of Scotland. The participants were allocated to either a SIT group (n = 26, 14 boys and 12 girls, 16.9 ± 0.3 years) or a non-exercising control group (CONT) (n = 23, 14 boys and 9 girls, 16.8 ± 0.6 years). Measures of height, weight, body mass index (BMI), physical activity and aerobic fitness were assessed preand post-SIT intervention. V̇O2max was estimated from results of the 20-m multi-stage fitness test (MSFT). Fasting blood was sampled preand post-intervention from the antecubital forearm vein. A volume of 6 ml was sampled and analysed for fasting plasma insulin, fasting blood glucose, homeostasis model of HOMA-IR, HOMA-S% and HOMA-β% using validated procedures. The SIT group performed 21 sessions over 7 consecutive weeks consisting of four to six sets of 30s maximal “all-out” running sprints interspersed with 30-s rest intervals. The CONT group were instructed to continue with their normal daily activities. The CONT group experienced a small but significant decline in V̇O2max (46.6 ± 8.0 vs. 43.9 ± 7.0 ml · kg · min, P = 0.01) from preto post-SIT intervention. Aerobic fitness was maintained, and significant improvements were observed in the SIT group for fasting plasma insulin (P = 0.04), HOMA-S% (P = 0.01) and HOMA-β % (P = 0.001). In conclusion 7 weeks of schoolbased SIT during the first semester following a summer vacation improves insulin sensitivity and prevents an associated decrease in aerobic fitness. The present study supports the contention that SIT routines may be a physiologically effective and feasible exercise modality for incorporation into school PE routines.

Cardiometabolic health benefits of a six-week high-intensity interval training intervention : a case study

In recent years, there has been recognition of the influence that English Premier League (EPL) football clubs can have in attracting men from disadvantaged groups to physical activity and health improvement programmes. Despite attempts to align Football in the Community (FitC) programmes with suitable evaluation procedures, there remains limited evaluative empirical evidence. This article outlines the research undertaken as a result of a formal collaboration with Everton Football Club’s FitC scheme (Everton in the Community). This research was conducted during a period of 36 months immersed practitioner research. Men from disadvantaged, hard-to-reach (HTR) populations often display a complex array of health issues. Understanding the wider determinants that prohibit engagement in physical activity and health behaviours amongst such populations is therefore important for the development of physical activity and health promotion with HTR men. The research investigates the distinct barriers that men from low socioeconomic groups encounter when attempting to engage in physical activity and positive health-related behaviours. The research explores the motivations driving participant engagement in a FitC men’s physical activity and health programme and the psychosocial impact of regular participation. Following the ethical approval, a series of relaxed and informal one-to-one semistructured interviews were conducted with six programme participants (whom had been regularly engaged for a period of 12 weeks to 36 months). An interview schedule was developed alongside conceptual themes. Data were collected by a digital recorder, transcribed verbatim and analysed by the researcher using narrative thematic analysis. A number of environmental and psychosocial barriers to engagement in regular physical activity and positive health-related behaviours are identified: social cultural norms, pressures and stresses of everyday life and addictive personality traits. Psychosocial motivations for joining the programme emerged, and the “pull” of the brand of the EPL football club is identified as a significant influencing factor. The impact of regular engagement in the programme is discussed, namely, improvements to psychological health and social wellbeing. Implications for practice are outlined. This article extends, supports and challenges the findings of previous literature and is crucial for developing and extending knowledge that can lead to the development of this and future physical activity and health engagement programmes targeting disadvantaged, HTR male populations.