Repeat trials of a race walker were analyzed to ascertain the contribution to energy changes made by the lower limb muscles. A sagittal plane link segment model was used to calculate mechanical powers at the hip, knee and ankle. The ankle plantarflexors provided the major energy necessary to propel the body forward. Muscles about the hip contribute to a lesser extent via energy generation and transfer. At the knee, the muscles acted mainly as energy absorbers and did not contribute to forward propulsion. Mechanical powers calculated for the race walker were compared to other forms of locomotion. Patterns unique to the race walker were identified and discussed.
Scott C. White and David Winter
Kayla Regan, Felicia White, David Harvey and Laura E. Middleton
Exercise and mental stimulation may improve cognition, physical function, and well-being of people with dementia (PWD) and older adults more generally. This study evaluated changes in physical function, physical activity, exercise self-efficacy, and mental well-being with participation in Minds in Motion®, a weekly exercise and mental stimulation program for PWD (n = 343) and care partners (n = 318). Most physical function measures improved among PWD and care partners (endurance, upper and lower body strength, upper body flexibility; ps ≤ .009). Participants also reported a significant increase in weekly frequency, duration, and intensity of physical activity (ps < .001) and in mental well-being (p < .001). Exercise self-efficacy did not change (p = .16). These results suggest that Minds in Motion® yields improvements in physical function, which may translate into better functional abilities for PWD and improved ability for their partners to care for people living with dementia.
David A. White, Youngha Oh and Erik A. Willis
Background: Research suggests that accumulating moderate to vigorous physical activity (MVPA) in longer continuous bouts may have beneficial effects on metabolic syndrome risk factors. The objective of this study was to examine the independent associations of MVPA bout patterns on metabolic syndrome risk factors among a nationally representative sample of youth. Methods: Results are based on 3165 children and adolescents (6–18 y old) from the 2003–2006 National Health and Nutrition Examination Survey. Accelerometers measured MVPA accumulated in bouts of: <5, 5 to 10, and ≥10 minutes over 7 days. Participants were categorized into quartiles based on percentage of each bout duration. Sensitivity analysis was conducted using 3 versions of MVPA cut points for youth. A series of general linear models were used to compare metabolic syndrome risk factors between groups. Results: Youth participating in longer continuous bouts of MVPA had lower body mass index percentile (P < .02), waist circumference (WC) (P < .01), WC percentile (P < .02), and waist to height ratio (P < .01) than youth participating in shorter bouts of MVPA. When analyzed for interactions between MVPA and bout pattern quartile, only 1 cut point showed a significant interaction for WC and WC percentile. Conclusion: Longer continuous bouts of MVPA had beneficial effects on body anthropometrics and weight status, although these effects may be moderated by total MVPA.
Jane McKay, Ailsa G. Niven, David Lavallee and Alison White
Following the theoretical framework of Lazarus and Folkman (1984), recently adapted to sport (Fletcher, Hanton, & Mellalieu, 2006), 12 elite UK track athletes (M age = 22.7; SD = 2.4 years) participated in semistructured interviews to identify sources of strain. Inductive content analysis identified 11 general dimensions of sources of strain from 664 meaning units, which were subsequently categorized into competitive, organizational, and personal domains. Several sources of strain (e.g., competitive concerns, pressure to perform) were consistent with previous research supporting the suggestion that a core group of stressors may be evident across sports although several sources of strain appeared to be more pertinent to track athletes (e.g., social evaluation and self-presentation concerns) highlighting the need to consider group differences.
Lance Ratcliff, Sareen S. Gropper, B. Douglas White, David M. Shannon and Kevin W. Huggins
This study compared type of habitual exercise and meal form on diet-induced thermogenesis (DIT) in 29 men age 19–28 yr. Resting metabolic rate (RMR) and DIT response to solid-meal (bar) vs. liquid-meal (shake) ingestion were measured via indirect calorimetry; classifications were sedentary (n = 9), endurance trained (n = 11), or resistance trained (n = 9). Height, weight, and body composition (using bioelectrical impedance) were measured for each subject. Energy expenditure was determined before and every 30 min after meal consumption for 210 min. RMR was significantly (p = .045) higher in the endurance- and resistance-trained groups. However, when expressed per kilogram fat-free mass (FFM; relative RMR), differences were not significant. Both DIT (kcal/min) and relative DIT (kcal · min−1 · kg FFM−1) significantly increased with time (p < .0001) from RMR for each meal form. There was no significant exercise-group effect on DIT or relative DIT. There was a significant (p = .012) effect of meal form on DIT; shakes elicited a higher DIT. This significant difference was not found for relative DIT. There was a significant interaction between group and meal form for DIT (p = .008) and relative DIT (p < .0001). Shakes elicited a significantly greater DIT (p = .0002) and relative DIT (p = .0001) in the resistance-trained group. In the sedentary group, relative DIT from shakes was significantly lower than from bars (p = .019). In conclusion, habitual exercise appears to increase RMR, and meal form may impart changes in relative DIT depending on exercise status.
Hugh H.K. Fullagar, Rob Duffield, Sabrina Skorski, David White, Jonathan Bloomfield, Sarah Kölling and Tim Meyer
The current study examined the sleep, travel, and recovery responses of elite footballers during and after long-haul international air travel, with a further description of these responses over the ensuing competitive tour (including 2 matches).
In an observational design, 15 elite male football players undertook 18 h of predominantly westward international air travel from the United Kingdom to South America (–4-h time-zone shift) for a 10-d tour. Objective sleep parameters, external and internal training loads, subjective player match performance, technical match data, and perceptual jet-lag and recovery measures were collected.
Significant differences were evident between outbound travel and recovery night 1 (night of arrival; P < .001) for sleep duration. Sleep efficiency was also significantly reduced during outbound travel compared with recovery nights 1 (P = .001) and 2 (P = .004). Furthermore, both match nights (5 and 10), showed significantly less sleep than nonmatch nights 2 to 4 and 7 to 9 (all P < .001). No significant differences were evident between baseline and any time point for all perceptual measures of jet-lag and recovery (P > .05), although large effects were evident for jet-lag on d 2 (2 d after arrival).
Sleep duration is truncated during long-haul international travel with a 4-h time-zone delay and after night matches in elite footballers. However, this lost sleep appeared to have a limited effect on perceptual recovery, which may be explained by a westbound flight and a relatively small change in time zones, in addition to the significant increase in sleep duration on the night of arrival after the long-haul flight.
Noah X. Tocci, David R. Howell, Dai Sugimoto, Corey Dawkins, Amy Whited and Donald Bae
High elbow torque during a pitch may contribute to injury risk. Our objective was to determine the pitch mechanics associated with elbow varus torque in youth baseball pitchers. Eighteen male youth pitchers (age = 15.5 ± 1.6 years) threw 3 fastballs and 3 change-ups from a windup position while undergoing 3-dimensional kinematic analysis. Independent variables included ball release point distance, stride length, lateral pelvic tilt, and ball velocity. Two multiple regression models, separated by pitch type (fastball, change-up) were used to determine the association of independent variables with peak varus torque at the elbow. Fastball and change-up regression models indicated that stride length (β = 0.301, p = .015; β = 0.46, p < .001, respectively) and lateral pelvic tilt (β = −0.50, p < .001; β = −0.25, p = .04, respectively) were significantly associated with peak elbow varus torque. During fastballs, pitch velocity was significantly associated with peak elbow varus torque (β = 0.38, p = .002), while release point distance was significantly associated with peak elbow varus torque during change-ups (β = −0.33, p = .015). Youth pitchers with longer strides and less lateral pelvic tilt demonstrated greater elbow torque regardless of pitch type, while the association of ball velocity and release point to elbow varus torque was dependent on pitch type.
Blake D. McLean, David Buttifant, Christopher J. Gore, Kevin White, Carsten Liess and Justin Kemp
Little research has been done on the physiological and performance effects of altitude training on team-sport athletes. Therefore, this study examined changes in 2000-m time-trial running performance (TT), hemoglobin mass (Hbmass), and intramuscular carnosine content of elite Australian Football (AF) players after a preseason altitude camp.
Thirty elite AF players completed 19 days of living and training at either moderate altitude (~2130 m; ALT, n = 21) or sea level (CON, n = 9). TT performance and Hbmass were assessed preintervention (PRE) and postintervention (POST1) in both groups and at 4 wk after returning to sea level (POST2) in ALT only.
Improvement in TT performance after altitude was likely 1.5% (± 4.8–90%CL) greater in ALT than in CON, with an individual responsiveness of 0.8%. Improvements in TT were maintained at POST2 in ALT. Hbmass after altitude was very likely increased in ALT compared with CON (2.8% ± 3.5%), with an individual responsiveness of 1.3%. Hbmass returned to baseline at POST2. Intramuscular carnosine did not change in either gastrocnemius or soleus from PRE to POST1.
A preseason altitude camp improved TT performance and Hbmass in elite AF players to a magnitude similar to that demonstrated by elite endurance athletes undertaking altitude training. The individual responsiveness of both TT and Hbmass was approximately half the group mean effect, indicating that most players gained benefit. The maintenance of running performance for 4 wk, despite Hbmass returning to baseline, suggests that altitude training is a valuable preparation for AF players leading into the competitive season.
Susan B. Sisson, Ashley E. Gibson, Kevin Short, Andrew W. Gardner, Teresa Whited, Candace Robledo and David M. Thompson
The purpose of this study was to determine if light physical activity (LPA) minimizes the impairment of cardiometabolic risk factors following a typical meal in adolescents. Eighteen adolescents (50% male, 14.8 ± 2.3 yrs) consumed a meal (32% fat, 14% protein, 53% carbohydrate), then completed a walking (1.5mph for 45 min of each hour) or sitting treatment for 3 hr in randomized order on separate days. Following the meal, HDL cholesterol declined 4.8% but remained higher during walking at 3 hr (42.1mg/dl ± 9.3) than sitting (8.4% decline; 40.5mg/dL ± 9.9; treatment × time interaction, p < .03). The 3-hr insulin was lower after walking (24.8μIU/ml ± 33.4) than sitting (37.8μIU/ml ± 34.7; treatment × time interaction, p < .0001). Triglycerides increased by ~40% above baseline at 1 and 2 hr, with higher values for walking (treatment × time interaction, p < .02). However by 3 hr, triglycerides were not different from baseline. Area under the curve (AUC) analyses were not significantly different between treatments for any outcomes. Although minor, LPA appears to mitigate the undesirable postprandial changes in HDL cholesterol and insulin but not triglycerides, following a typical meal in adolescents.