Effects of external loads on postural sway during quiet stance in adults aged 20-80 years.

The purpose of this study was to investigate the effects of holding external loads on postural sway during upright stance across age decades. Sixty-five healthy adults (females, n = 35), aged 18-80 years were assessed in four conditions; (1) standing without holding a load, holding a load corresponding to 5% body mass in the (2) left hand, (3) right hand and (4) both hands. The centre of pressure (COP) path length and anteroposterior and mediolateral COP displacement were used to indirectly assess postural sway. External loading elicited reductions in COP measures of postural sway in older age groups only (P < 0.05). No changes were observed in younger or intermediate aged adults (P > 0.05). Holding external loads during standing is relevant to many activities of daily living (i.e. holding groceries). The reduction in postural sway may suggest this type of loading has a stabilising effect during quiet standing among older adults.

The effects of arm crank ergometry, cycle ergometry and treadmill walking on postural sway in healthy older females.

Older adults are increasingly being encouraged to exercise but this may lead to muscle fatigue, which can adversely affect postural stability. Few studies have investigated the effects of upper body exercise on postural sway in groups at risk of falling, such as the elderly. The purpose of this study was to compare the effects arm crank ergometry (ACE), cycle ergometry (CE) and treadmill walking (TM) on postural sway in healthy older females. In addition, this study sought to determine the time necessary to recover postural control after exercise. A total of nine healthy older females participated in this study. Participants stood on a force platform to assess postural sway which was measured by displacement of the centre of pressure before and after six separate exercise trials. Each participant completed three incremental exercise tests to 85% of individual's theoretical maximal heart rate (HRMAX) for ACE, CE and TM. Subsequent tests involved 20-min of ACE, CE and TM exercise at a relative workload corresponding to 50% of each individual's predetermined heart rate reserve (HRE). Post fatigue effects and postural control recovery were measured at different times after exercise (1, 3, 5, 10, 15 and 30-min). None of the participants exhibited impaired postural stability after ACE. In contrast, CE and TM elicited significant post exercise balance impairments, which lasted for ∼ 10 min post exercise. We provide evidence of an exercise mode which does not elicit post exercise balance impairments. Older adults should exercise caution immediately following exercise engaging the lower limbs to avoid fall risk.

Effect of heavy back squats on repeated sprint performance in trained men.

AIM: This study examined the impact of post activation potentiation on repeated sprint performance in trained Rugby Union players. METHODS: Ten, male, professional Rugby Union players (mean age=25.2±5.02 years) performed 7, 30-meter sprints, separated by 25 seconds, 4 minutes following back squats (90% 1 repetition maximum) or a control condition performed in a counterbalanced order. RESULTS: Significant condition X sprint interactions for 10-meter (P=0.02) and 30-meter (P=0.05) indicated that times were significantly faster in the PAP condition for sprints 5, 6 and 7 across both distances. Fatigue rate was also significantly lower in the PAP condition for 10-meter (P=0.023) and 30-meter (P=0.006) sprint running speed. CONCLUSION: This study evidences that a heavy resistance exercise stimulus administered four minutes prior to repeated sprints can offset the decline in sprint performance seen during subsequent maximal sprinting over 10 and 30-meters in Rugby Union players.

Acute caffeine ingestion enhances performance and dampens muscle pain following resistance exercise to failure.

This double-blind, within-subjects experiment examined the effects of acute caffeine ingestion on perceptions of muscle pain following a bout of high-intensity, upper-body resistance exercise to failure. Moderately trained males (N.=18) ingested a dose of caffeine (5 mg · kg-1) or placebo in a randomised and counterbalanced order and 1 hour later completed bench press exercise to failure at an intensity of 60% 1 repetition maximum. Repetitions completed was taken as a measure of performance, peak heart rate was determined via heart rate telemetry during the exercise bout, rating of perceived exertion (RPE) and upper body muscle pain was recorded immediately upon failure of the exercise task and peak blood lactate concentration was determined post-exercise. Caffeine resulted in improved repetitions to failure (t [17]=3.119, P=0.006), greater peak blood lactate (t [17] =5.080, P=0.0001) and lower RPE (t 17=-3.431, P=0.003) compared to placebo. Muscle pain perception was also significantly lower in the caffeine condition compared to placebo (t [17]=-2.567, P=0.04). These results support prior studies using aerobic based exercise modes in suggesting that caffeine ingestion can dampen exercise-induced muscle pain. Specifically, caffeine ingestion enhances muscular strength performance and reduces upper body muscle pain perception immediately following a bout of high-intensity resistance exercise to failure.