This investigation examined whether low sodium (Na+) (LNA; 68 mEq Na+·d-1) or moderate Na+ (MNA; 137 mEq Na+.d-1) intake allowed humans to maintain health, exercise, and physiologic function during 10 days of prolonged exercise-heat acclimation (HA). Seventeen volunteers, ages 19 to 21, consumed either LNA (n=8) or MNA (n=9) during HA (41°C, 21% RH; treadmill walking for 30 min.h-1, 8 h·d-1 at 5.6 kmh-l, 5% grade), which resulted in significantly reduced heart rate, rectal temperature, and urine Na+ for both groups. There were few between-diet differences in any variables measured. Mean plasma volume in LNA expanded significantly less than in MNA by Days 11 and 15, but reached the MNA level on Day 17 (+12.3 vs. +12.4%). The absence of heat illness, the presence of normal physiologic responses, and the total distance walked indicated successful and similar HA with both levels of dietary Na+.
Lawrence E. Armstrong, Roger W. Hubbard, E. Wayne Askew, Jane P. De Luca, Catherine O'Brien, Angela Pasqualicchio and Ralph P. Francesconi
Michael L. Mestek, John C. Garner, Eric P. Plaisance, James Kyle Taylor, Sofiya Alhassan and Peter W. Grandjean
The purpose of this study was to compare blood lipid responses to continuous versus accumulated exercise. Nine participants completed the following conditions on separate occasions by treadmill walking/jogging at 70% of VO2max : 1) one 500-kcal session and 2) three 167 kcal sessions. Total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG) concentrations were measured from serum samples obtained 24 h prior to and 24 and 48 h after exercise. All blood lipid responses were analyzed in 2 (condition) × 3 (time) repeated measures ANOVAs. HDL-C increased by 7 mg/dL over baseline at 48 h post-exercise with three accumulated sessions versus 2 mg/dL with continuous exercise (P < 0.05). Triglyceride concentrations were unchanged in both conditions. These findings suggest that three smaller bouts accumulated on the same day may have a modestly greater effect for achieving transient increases in HDL-C compared to a continuous bout of similar caloric expenditure.
Charity B. Breneman, Christopher E. Kline, Delia West, Xuemei Sui and Xuewen Wang
This study investigated the acute effect of exercise on sleep outcomes among healthy older women by comparing days with structured exercise versus days without structured exercise during 4 months of exercise training. Participants (n = 51) in this study had wrist-worn actigraphic sleep data available following at least 3 days with structured exercise and 3 days without structured exercise at mid-intervention and at the end of intervention. The exercise intervention was treadmill walking. Multilevel models were used to examine whether structured exercise impacted sleep outcomes during the corresponding night. Overall, 1,362 nights of data were included in the analyses. In unadjusted and adjusted models, bedtimes were significantly earlier on evenings following an acute bout of structured exercise than on evenings without structured exercise. No other sleep parameters differed between exercise and nonexercise days. Understanding the effects of exercise on sleep in this understudied population may help to improve their overall sleep quality.
Richard A. Boileau, Edward McAuley, Demetra Demetriou, Naveen K. Devabhaktuni, Gregory L. Dykstra, Jeffery Katula, Jane Nelson, Angelo Pascale, Melissa Pena and Heidi-Mai Talbot
A trial was conducted to examine the effect of moderate aerobic exercise training (AET) on cardiorespiratory (CR) fitness. Previously sedentary participants, age 60-75 years, were randomly assigned to either AET treatment or a control group for 6 months. The AET consisted of walking for 40 min three times/week at an intensity that elevated heart rate to 65% of maximum heart rate reserve. The control group performed a supervised stretching program for 40 min three times/week. CR fitness was assessed before and after the treatments during a grade-incremented treadmill walking test. Both absolute and relative peak V̇O2 significantly increased (p < .01) in the AET group, whereas they decreased modestly in the control group. Maximum treadmill time increased significantly (p < .01) in the AET group relative to the control group. These results indicate that CR fitness as measured by peak V̇O2 modestly improves in the elderly with a moderate-intensity, relatively long-term aerobic exercise program.
David Alexander Leaf and Holden MacRae
The purpose of this study was to examine the criterion-related validity of two indirect measures of energy expenditure (EE): American College of Sports Medicine (ACSM) predictive equations, and estimated EE based on the Caltrac accelerometer. These measures were compared in 20 community-dwelling older men and women (mean age 71 years). The strength of the relationships among major determinants of EE during self-selected speeds of treadmill and outdoor walking was also examined. EE measured by respiratory gas analysis during an exercise stress test was highly correlated with ACSM predictive equations and poorly correlated with Caltrac. Multivariate regression equations were established to evaluate the ability of independent variables—body weight and height, age, and preferred treadmill walking speed—to predict EE (dependent variable). It was concluded that the ACSM predictive equations are suitable for use in elderly individuals, and that the apparent differences in the relationships between treadmill and outdoor walking speeds on EE deserve further investigation.
Joanna Scurr, Jennifer White and Wendy Hedger
This study aimed to assess the trajectory of breast displacement in 3 dimensions during walking and running gait, as this may improve bra design and has yet to be reported. Fifteen D-cup participants had reflective markers attached to their nipples and trunk to monitor absolute and relative breast displacement during treadmill walking (5 kph) and running (10 kph). During the gait cycle, the breast followed a figure-of-eight pattern with four movement phases. Despite a time lag in resultant breast displacement compared with the trunk, similar values of breast displacement were identified across each of the four phases. Fifty-six percent of overall breast movement was vertical, suggesting that 3-D assessment and the elimination of trunk movement in 6 degrees of freedom are essential to accurately report breast displacement during the gait cycle.
Melissa N. Galea, Steven R. Bray and Kathleen A. Martin Ginis
This study aimed to identify barriers and facilitators associated with walking for exercise among people who experience intermittent claudication. Fifteen individuals (7 men and 8 women) participated in 3 focus groups that were tape-recorded and content analyzed. A social-cognitive framework was used to categorize barriers and facilitators as those related to the person, to the activity, or to the environment. Variables identified included those specific to intermittent claudication and those common among the general population. Barriers to walking included irregular or graded walking surfaces, uncertainty about the outcome of walking, ambiguity regarding pain, the need to take rest breaks, and the presence of leg pain. Facilitating factors included availability of a resting place, use of cognitive coping strategies, companionship support, and availability of a treadmill-walking program. Findings are interpreted in light of current research on exercise determinants and encourage prospective examinations of the predictive validity of these factors for walking.
Philip D. Tomporowski, Catherine L. Davis, Kate Lambourne, Mathew Gregoski and Joseph Tkacz
The short-term aftereffects of a bout of moderate aerobic exercise were hypothesized to facilitate children’s executive functioning as measured by a visual task-switching test. Sixty-nine children (mean age = 9.2 years) who were overweight and inactive performed a category-decision task before and immediately following a 23-min bout of treadmill walking and, on another session, before and following a nonexercise period. The acute bout of physical activity did not influence the children’s global switch cost scores or error rates. Age-related differences in global switch cost scores, but not error scores, were obtained. These results, in concert with several studies conducted with adults, fail to confirm that single bouts of moderately intense physical activity influence mental processes involved in task switching.
Richard R. Rosenkranz, Sara K. Rosenkranz and Casey Weber
This study sought to assess criterion validity of the Actical monitor step-count function in children via ankle and waist placement, compared with observed video recordings. Children attending a summer program (12 boys, 7 girls, mean age = 9.6yrs, range 7–11yrs) wore two synchronized Acticals, attached at the ankle (AA) and waist (AW). Children performed treadmill walking at varying speeds, and two research assistants counted steps using observed video recordings (OVR). Results showed high correlations for AW-OVR (r = .927, p < .001) and AA-OVR (r = .854, p < .001), but AW and AA were significantly lower than OVR (t > 11.2, p < .001). AW provided better step estimates than AA for step rates above 130 steps per minute. In contrast, AA was superior to AW for slow walking, and measured more steps during the (nontreadmill) program time. Overall, the Actical monitor showed good evidence of validity as a measure of steps in children for population-based studies.
Jeffrey P. Kaipust, Jessie M. Huisinga, Mary Filipi and Nicholas Stergiou
The purpose of this study was to determine the differences in gait variability between patients with multiple sclerosis (MS) and healthy controls during walking at a self-selected pace. Methods: Kinematics were collected during three minutes of treadmill walking for 10 patients with MS and 10 healthy controls. The Coefficient of Variation (CoV), the Approximate Entropy (ApEn) and the Detrended Fluctuation Analysis (DFA) were used to investigate the fluctuations present in stride length and step width from continuous strides. Results: ApEn revealed that patients with MS had significantly lower values than healthy controls for stride length (p < .001) and step width (p < .001). Conclusions: ApEn results revealed that the natural fluctuations present during gait in the stride length and step width time series are more regular and repeatable in patients with MS. These changes implied that patients with MS may exhibit reduced capacity to adapt and respond to perturbations during gait.