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Balance control during overground walking was assessed in 10 young (23.6 ± 3.4) and 10 older (71.0 ± 5.5 years) healthy females during free gaze, and when fixating or tracking another person in an everyday use waiting room. Balance control was characterised by medial/lateral sacrum acceleration dispersion, and gaze fixations were simultaneously assessed with eye tracking equipment. The results showed decreased balance control when fixating a stationary (p = 0.003, gav = 0.19) and tracking a walking (p = 0.027, gav = 0.16) person compared to free gaze. The older adults exhibited reduced baseline stability throughout, but the decrease caused by the visual tasks was not more profound than the younger adults. The decreased balance control when fixating on or tracking the observed person was likely due to more challenging conditions for interpreting retinal flow, which facilitated less reliable estimates of self-motion through vision. The older adults either processed retinal flow during the tasks as effectively as the young adults, or they adopted a more rigid posture to facilitate visual stability, which masked any ageing effect of the visual tasks. The decrease in balance control, the first to be shown in this context, may warrant further investigation in those with ocular or vestibular dysfunction.

Helen Dixon,1 Catherine E Baker,2 Julien S Baker,3 Susan Dewhurst,4 Lawrence D Hayes4 1School of Human Sciences, London Metropolitan University, London, 2English Institute of Sport, Bisham Abbey National Sports Center, Buckinghamshire, 3Institute of Clinical Exercise and Health Science, University of the West of Scotland, Hamilton, 4Department of Medical and Sport Sciences, University of Cumbria, Lancaster, UK Abstract: This study investigated the effect of sodium bicarbonate (NaHCO3–) ingestion on the Yo-Yo intermittent recovery test 1 (IR1). We tested the hypothesis that acute ingestion of NaHCO3– would increase blood lactate concentrations [BLa], enhance performance, and reduce rating of perceived exertion (RPE) in the Yo-Yo IR1. Eight recreationally active males (N=8, age: 26±4 yr, height: 178±6 cm, body mass: 82±10 kg) participated in the Yo-Yo IR1 on two separate occasions, separated by 1 wk, in a randomized crossover design. Following familiarization, during seated rest, participants’ pretest [BLa] was taken, and participants then consumed either a placebo of 0.3 g·kg–1 body weight sodium chloride or 0.3 g·kg–1 body weight NaHCO3–. Sixty minutes postingestion, a standardized warm-up preceded the Yo-Yo IR1. Upon completion, postexercise [BLa] (mmol·L–1), RPE (arbitrary units) and Yo-Yo IR1 time to fatigue (s) were recorded. Paired t-test revealed a small but significant improvement in Yo-Yo IR1 performance under the NaHCO3– condition (610±267 sec), compared to the placebo condition (556±259 sec; p=0.01; Cohen’s d=0.20). [BLa] increased more under the NaHCO3– condition (1.6±0.7 to 17.5±5.2 mmol·L–1; p<0.001; Cohen’s d=4.29), compared to the placebo condition (2.0±0.7 to 11.5±5.0 mmol&amp

Food shopping is an important aspect of maintaining independence and social interaction in older age. Carriage of shopping bags alters the body's weight distribution which, depending on load distribution, could potentially increase instability during standing and walking. The study examined the effect of carrying UK style shopping bags on static postural stability and gait in healthy older and young females. Nine older (71.0 ± 6.0 years) and 10 young (26.7 ± 5.2 years) females were assessed in five conditions carrying no bags, one 1.5 kg bag in each hand, one 3 kg bag in each hand, one 1.5 kg bag in preferred hand, one 3 kg bag in preferred hand. Antero-posterior and medio-lateral displacement, and 95% ellipse area from a 30 s quiet standing were used for postural stability assessment. Stride length and its coefficient of variation, total double support time, step asymmetry and gait stability ratio were calculated from 1 min treadmill walking at self-selected speed for gait assessment. Carrying shopping bags did not negatively affect postural stability or gait variables, in either group. Further, in older individuals, a decrease in sway velocity was found when holding bags during the postural stability assessment (p < 0.05), suggesting that carriage of bags, irrespective of the load distribution, may have a stabilising effect during quiet standing. These results should help to alleviate concerns regarding safety of carrying shopping bags and help encourage shopping, both as a social and as a physical activity.

Visual information is used for postural stabilization in humans. However, little is known about how eye movements prevalent in everyday life interact with the postural control system in older individuals. Therefore, the present study assessed the effects of stationary gaze fixations, smooth pursuits, and saccadic eye movements, with combinations of absent, fixed and oscillating large-field visual backgrounds to generate different forms of retinal flow, on postural control in healthy young and older females. Participants were presented with computer generated visual stimuli, whilst postural sway and gaze fixations were simultaneously assessed with a force platform and eye tracking equipment, respectively. The results showed that fixed backgrounds and stationary gaze fixations attenuated postural sway. In contrast, oscillating backgrounds and smooth pursuits increased postural sway. There were no differences regarding saccades. There were also no differences in postural sway or gaze errors between age groups in any visual condition. The stabilizing effect of the fixed visual stimuli show how retinal flow and extraocular factors guide postural adjustments. The destabilizing effect of oscillating visual backgrounds and smooth pursuits may be related to more challenging conditions for determining body shifts from retinal flow, and more complex extraocular signals, respectively. Because the older participants matched the young group's performance in all conditions, decreases of posture and gaze control during stance may not be a direct consequence of healthy aging. Further research examining extraocular and retinal mechanisms of balance control and the effects of eye movements, during locomotion, is needed to better inform fall prevention interventions.

Leg stiffness is an important performance determinant in several sporting activities. This study evaluated the criterion-related validity and reliability of 2 field-based leg stiffness devices, Optojump Next® (Optojump) and Myotest Pro® (Myotest) in different testing approaches. Thirty-four males performed, on 2 separate sessions, 3 trials of 7 maximal hops, synchronously recorded from a force platform (FP), Optojump and Myotest. Validity (Pearson's correlation coefficient, r; relative mean bias; 95% limits of agreement, 95%LoA) and reliability (coefficient of variation, CV; intraclass correlation coefficient, ICC; standard error of measurement, SEM) were calculated for first attempt, maximal attempt, and average across 3 trials. For all 3 methods, Optojump correlated highly to the FP (range r =.98-.99) with small bias (range 0.91-0.92, 95%LoA 0.86-0.98). Myotest demonstrated high correlation to FP (range r =.81-.86) with larger bias (range 1.92-1.93, 95%LoA 1.63-2.23). Optojump yielded a low CV (range 5.9% to 6.8%), high ICC (range 0.82-0.86), and SEM ranging 1.8-2.1 kN/m. Myotest had a larger CV (range 8.9% to 13.0%), moderate ICC (range 0.64-0.79), and SEM ranging from 6.3 to 8.9 kN/m. The findings present important information for these devices and support the use of a time-efficient single trial to assess leg stiffness in the field.

The effects of long-term participation in Scottish country dance on body composition, functional ability, and balance in healthy older females were examined. Participants were grouped into dancers and physically active nondancers (ages 60-70 and 70-80 for both groups). Physical activity, body composition (body-mass index, skinfold thickness, waist-to-hip ratio), functional ability (6-min walk distance, 6-m walk time, 8-ft up-andgo time, lower body flexibility, shoulder flexibility), and static balance were measured. Younger dancers and physically active nondancers had similar 6-min walk distance, 6-m walk time, and 8-ft up-and-go time results; however, while older dancers performed similarly to younger dancers, older physically active nondancers performed poorer than their younger counterparts (p .05). Body composition and static balance were the same for all groups. Regular physical activity can maintain body composition and postural stability with advancing age; however, Scottish country dance can delay the effects of aging on locomotion-related functional abilities.

Marching with essential survival equipment is a fundamental military exercise. A consequence of this increased load is an increased risk of dehydration. Dehydration may have fatal consequences in a combat situation where performance must be optimal. This risk can be minimized with an understanding of the additional fluid needs of soldiers marching when loaded compared to unloaded. The aim of this study was to quantify fluid loss caused by marching with a loaded Bergen rucksack and webbing of 33.5 kg for 45 minutes when compared to unloaded carriage in eight healthy male officer cadets (age, 20.5 ± 0.9 years; body mass 80.2 ± 9.2 kg). The findings demonstrate an increased rate of sweat loss (0.6 ± 0.2 L·h-1 to 1.2 ± 0.4 L·h-1; p<0.001) and increased average heart rate (105.5 ± 17.7 beats·min-1 to 136.6 ± 28.3 beats·min-1; p<0.001) for unloaded and loaded trial respectively. Urine osmolality significantly increased pre- to post-march (p<0.05), however there was no difference in this increase between the loaded and unloaded trial. The present study demonstrated that marching with a loaded rucksack and webbing increased sweat rate by 100% compared to the same march with no additional load. For soldiers to prevent dehydration and the potential detrimental effects on performance, fluid replacement should also be doubled when marching with loading in a temperate environment, however individual differences in sweat rate should be taken into account.

Functional tests are commonly used to evaluate the functional ability of older individuals; however, intraday reliability and sensitivity are required to enable informed decisions on whether repeated trials are necessary and to ensure that the values obtained from a single session are a patient's true score. This study aimed to investigate the intraday reliability and sensitivity of four commonly used functional tests in older individuals. Seventy-one healthy older women (mean [SD]: age, 71.7 [7.3] yrs; body mass, 64.8 [10.2] kg; stature, 1.58 [0.07] m) performed the 6-m maximum walking speed, timed 8-foot up-and-go, chair sit-and-reach, and back scratch tests three times in one single session, with 1 min between trials. Reliability between all trials was examined using intraclass correlation coefficient, and sensitivity was examined using typical error. All tests were highly reliable (intraclass correlation coefficient range, 0.89-0.99), indicating no need for a familiarization trial. Typical error between trials 2 and 1 were 0.06 m·s, 0.42 s, 1.13 cm, 0.92 cm for the 6-m maximum walking speed, timed 8-foot up-and-go, chair sit-and-reach, and back scratch tests, respectively. Practitioners should perform two trials to examine whether the difference between them is less than the typical error reported here. These results should help practitioners ensure that scores obtained from an individual from these functional tests are a true reflection of their functional ability rather than measurement error.