This study examined whether active commuting to and from school was associated with more frequent walking and cycling to other neighborhood destinations. Parents reported on free-time physical activity and frequency of active commuting among 1,643 South Australians (9–15 years), as well as their perceptions of risk associated with active commuting in the neighborhood. Groups were formed on the basis of active and motorized transport to and from school and compared on the frequency of walking and cycling to other neighborhood destinations. Those who actively commuted between home and school were approximately 30% more likely to actively commute to other neighborhood destinations, independent of age, free-time physical activity, and neighborhood risk. Active commuting to and from school is part of a broader habit of walking and cycling in the neighborhood among school age South Australians. The advantages of promoting active transport between home and school might extend beyond the energy expenditure of that journey alone.
James Dollman and Nicole R. Lewis
Lewis J. James and Susan M. Shirreffs
Weight categorized athletes use a variety of techniques to induce rapid weight loss (RWL) in the days leading up to weigh in. This study examined the fluid and electrolyte balance responses to 24-hr fluid restriction (FR), energy restriction (ER) and fluid and energy restriction (F+ER) compared with a control trial (C), which are commonly used techniques to induce RWL in weight category sports. Twelve subjects (six male, six female) received adequate energy and water (C) intake, adequate energy and restricted water (~10% of C; FR) intake, restricted energy (~25% of C) and adequate water (ER) intake or restricted energy (~25% of C) and restricted (~10% of C) water intake (F+ER) in a randomized counterbalanced order. Subjects visited the laboratory at 0 hr, 12 hr, and 24 hr for blood and urine sample collection. Total body mass loss was 0.33% (C), 1.88% (FR), 1.97% (ER), and 2.44% (F+ER). Plasma volume was reduced at 24 hr during FR, ER, and F+ER, while serum osmolality was increased at 24 hr for FR and F+ER and was greater at 24 hr for FR compared with all other trials. Negative balances of sodium, potassium, and chloride developed during ER and F+ER but not during C and FR. These results demonstrate that 24 hr fluid and/or energy restriction significantly reduces body mass and plasma volume, but has a disparate effect on serum osmolality, resulting in hypertonic hypohydration during FR and isotonic hypohydration during ER. These findings might be explained by the difference in electrolyte balance between the trials.
Ruth M. James, Sarah Ritchie, Ian Rollo and Lewis J. James
The aim of the current study was to investigate the influence of mouth rinsing carbohydrate at increasing concentrations on ~1 hr cycle time trial performance. Eleven male cyclists completed three experimental trials, following an overnight fast. Cyclists performed a ~1 hr time trial on a cycle ergometer, while rinsing their mouth for 5 s with either a 7% maltodextrin solution (CHO), 14% CHO or a taste-matched placebo (PLA) after every 12.5% of the set amount of work. Heart rate was recorded every 12.5% of the time trial, while RPE and GI comfort were determined every 25% of the time trial. The mouth rinse protocol influenced the time to complete the time trial (p < .001), with cyclists completing the time trial faster during 7% CHO (57.3 ± 4.5 min; p = .004) and 14% CHO (57.4 ± 4.1 min; p = .007), compared with PLA (59.5 ± 4.9 min). There was no difference between the two carbohydrate trials (p = .737). There was a main effect of time (P<0.001) for both heart rate and RPE, but no main effect of trial (p = .107 and p = .849, respectively). Scores for GI comfort ranged from 0–2 during trials, indicating very little GI discomfort during exercise. In conclusion, mouth rinsing and expectorating a 7% maltodextrin solution, for 5 s routinely during exercise was associated with improved cycle time trial performance approximately 1 h in duration. Increasing the carbohydrate concentration of the rinsed solution from 7% to 14% resulted in no further performance improvement.
Ian Rollo, Lewis James, Louise Croft and Clyde Williams
The purpose of the current study was to investigate the influence of ingesting a carbohydrate-electrolyte (CHO-E) beverage ad libitum or as a prescribed volume on 10-mile run performance and gastrointestinal (GI) discomfort. Nine male recreational runners completed the 10-mile run under the following 3 conditions: no drinking (ND; 0 ml, 0 g CHO), ad libitum drinking (AD; 315 ± 123 ml, 19 ± 7 g CHO), and prescribed drinking (PD; 1,055 ± 90 ml, 64 ± 5 g CHO). During the AD and PD trials, drinks were provided on completion of Miles 2, 4, 6, and 8. Running performance, speed (km/hr), and 10-mile run time were assessed using a global positioning satellite system. The runners’ ratings of perceived exertion and GI comfort were recorded on completion of each lap of the 10-mile run. There was a significant difference (p < .10) in performance times for the 10-mile race for the ND, AD, and PD trials, which were 72:05 ± 3:36, 71:14 ± 3:35, and 72:12 ± 3.53 min:s, respectively (p = .094). Ratings of GI comfort were reduced during the PD trial in comparison with both AD and ND trials. In conclusion, runners unaccustomed to habitually drinking CHO-E beverages during training improved their 10-mile race performance with AD drinking a CHO-E beverage, in comparison with drinking a prescribed volume of the same beverage or no drinking.
Gethin H. Evans, Jennifer Miller, Sophie Whiteley and Lewis J. James
The purpose of this study was to examine the efficacy of water and a 50 mmol/L NaCl solution on postexercise rehydration when a standard meal was consumed during rehydration. Eight healthy participants took part in two experimental trials during which they lost 1.5 ± 0.4% of initial body mass via intermittent exercise in the heat. Participants then rehydrated over a 60-min period with water or a 50 mmol/L NaCl solution in a volume equivalent to 150% of their body mass loss during exercise. In addition, a standard meal was ingested during this time which was equivalent to 30% of participants predicted daily energy expenditure. Urine samples were collected before and after exercise and for 3 hr after rehydration. Cumulative urine volume (981 ± 458 ml and 577 ± 345 mL; p = .035) was greater, while percentage fluid retained (50 ± 20% and 70 ± 21%; p = .017) was lower during the water compared with the NaCl trial respectively. A high degree of variability in results was observed with one participant producing 28% more urine and others ranging from 18–83% reduction in urine output during the NaCl trial. The results of this study suggest that after exercise induced dehydration, the ingestion of a 50 mmol/L NaCl solution leads to greater fluid retention compared with water, even when a meal is consumed postexercise. Furthermore, ingestion of plain water may be effective for maintenance of fluid balance when food is consumed in the rehydration period.
David J. Clayton, Gethin H. Evans and Lewis J. James
The purpose of this study was to examine the gastric emptying and rehydration effects of hypotonic and hypertonic glucose-electrolyte drinks after exercise-induced dehydration. Eight healthy males lost ~1.8% body mass by intermittent cycling and rehydrated (150% of body mass loss) with a hypotonic 2% (2% trial) or a hypertonic 10% (10% trial) glucose-electrolyte drink over 60 min. Blood and urine samples were taken at preexercise, postexercise, and 60, 120, 180, and 240 min postexercise. Gastric and test drink volume were determined 15, 30, 45, 60, 90, and 120 min postexercise. At the end of the gastric sampling period 0.3% (2% trial) and 42.1% (10% trial; p < .001) of the drinks remained in the stomach. Plasma volume was lower (p < .01) and serum osmolality was greater (p < .001) at 60 and 120 min during the 10% trial. At 240 min, 52% (2% trial) and 64% (10% trial; p < .001) of the drinks were retained. Net fluid balance was greater from 120 min during the 10% trial (p < .001). When net fluid balance was corrected for the volume of fluid in the stomach, it was greater at 60 and 120 min during the 2% trial (p < .001). These results suggest that the reduced urine output following ingestion of a hypertonic rehydration drink might be mediated by a slower rate of gastric emptying, but the slow gastric emptying of such solutions makes rehydration efficiency difficult to determine in the hours immediately after drinking, compromising the calculation of net fluid balance.
Liane S. Lewis, James Hernon, Allan Clark and John M. Saxton
The present study investigated the convergent validity of an interview-administered IPAQ long version (IPAQ-L) in an older population by comparison with objective accelerometry movement data. Data from 52 participants (mean age 67.9 years, 62% male) were included in the analysis. Treadmill derived (TM-ACC: 1,952–5,724 cpm) and free-living physical activity (PA) derived (FL-ACC: 760–5,724 cpm) accelerometer cut-points were used as criterion. IPAQ-L measures (total PA, leisure-time, walking-time, sedentary time) were significantly correlated with accelerometry (P ≤ .05). Differences in sex were observed. Bland-Altman Limits of Agreement analysis showed that the IPAQ-L overestimated PA in relation to accelerometry. Our results show that an interview-administered IPAQ-L shows low to moderate convergent validity with objective PA measures in this population but there may be differences between males and females which should be further investigated.
Liane S. Lewis, Barnabas Shaw, Srijit Banerjee, Pryscilla Dieguez, James Hernon, Nigel Belshaw and John M. Saxton
This nonblinded randomized controlled trial investigated the efficacy of a physical activity (PA) intervention underpinned by self-determination theory. Participants (N = 31, mean age 69 years [SD = 4.9]) diagnosed with bowel polyps were randomized to an active lifestyle program (ALP; n = 17) or standard care (n = 14). ALP received supervised exercise and counseling for 6 months. Both groups were followed up at 12 months. Outcomes were change in PA and behavioral regulation. Data were analyzed with intention to treat. At 6 months, differences were observed for behavioral regulation in favor of ALP (p < .05). PA differences were significant for leisure, walking, and vigorous in favor of ALP (p < .05). The self-determination theory can be an effective strategy for promoting PA behavior change in this population, but a larger trial is needed to further explore the utility of the self-determination theory in this context.
Mathew Hillier, Louise Sutton, Lewis James, Dara Mojtahedi, Nicola Keay and Karen Hind
The practice of rapid weight loss (RWL) in mixed martial arts (MMA) is an increasing concern but data remain scarce. The aim of this study was to investigate the prevalence, magnitude, methods, and influencers of RWL in professional and amateur MMA athletes. MMA athletes (N = 314; 287 men and 27 women) across nine weight categories (strawweight to heavyweight), completed a validated questionnaire adapted for this sport. Sex-specific data were analyzed, and subgroup comparisons were made between athletes competing at professional and amateur levels. Most athletes purposefully reduced body weight for competition (men: 97.2%; women: 100%). The magnitude of RWL in 1 week prior to weigh-in was significantly greater for professional athletes compared with those competing at amateur level (men: 5.9% vs. 4.2%; women: 5.0% vs. 2.1% of body weight; p < .05). In the 24 hr preceding weigh-in, the magnitude of RWL was greater at professional than amateur level in men (3.7% vs. 2.5% of body weight; p < .05). Most athletes “always” or “sometimes” used water loading (72.9%), restricting fluid intake (71.3%), and sweat suits (55.4%) for RWL. Coaches were cited as the primary source of influence on RWL practices (men: 29.3%; women: 48.1%). There is a high reported prevalence of RWL in MMA, at professional and amateur levels. Our findings, constituting the largest inquiry to date, call for urgent action from MMA organizations to safeguard the health and well-being of athletes competing in this sport.
Stephen A. Mears, Kathryn Dickinson, Kurt Bergin-Taylor, Reagan Dee, Jack Kay and Lewis J. James
Purpose: To examine the effect on short-duration, high-intensity cycling time-trial (TT) performance when a semisolid breakfast containing carbohydrate (CHO) or a taste- and texture-matched placebo is ingested 90 min preexercise compared with a water (WAT) control. Methods: A total of 13 well-trained cyclists (mean [SD]: age = 25  y, body mass = 71.1 [5.9] kg, height = 1.76 [0.04] m, maximum power output = 383  W, and peak oxygen uptake = 4.42 [0.53] L·min−1) performed 3 experimental trials examining breakfast ingestion 90 min before a 10-min steady-state cycle (60% maximum power output) and an ∼20-min TT (to complete a workload target of 376  kJ). Subjects consumed either WAT, a semisolid CHO breakfast (2 g carbohydrate CHO·kg−1 body mass), or a taste- and texture-matched placebo (PLA). Blood lactate and glucose concentrations were measured periodically throughout the rest and exercise periods. Results: The TT was completed more quickly in CHO (1120  s; P = .006) and PLA (1112  s; P = .030) compared with WAT (1146  s). Ingestion of CHO caused an increase in blood glucose concentration throughout the rest period in CHO (peak at 30-min rest = 7.37 [1.10] mmol·L−1; P < .0001) before dropping below baseline levels after the steady-state cycling. Conclusion: A short-duration cycling TT was completed more quickly when subjects perceived that they had consumed breakfast (PLA or CHO) 90 min prior to the start of the exercise. The improvement in performance is likely attributable to a psychological rather than physiological effect.