Carrying heavy asymmetrical loads increases postural sway during quiet standing in older adults.

Holding asymmetrical loads in the hands is common during many daily and occupational activities which, depending on the load mass, may alter postural stability. The purpose of this study was to determine the effect of load magnitude held asymmetrically in the hand on postural sway in older people. Eighteen healthy older adults (age 65.9 ± 5.7 years) were assessed in the following conditions; (1) standing without an external load (0%), (2) standing while holding a grocery bag containing 5%, (3) 10% and (4) 20% body mass in the dominant hand. The total displacement of the centre of pressure (COP) in the anteroposterior and mediolateral directions (cm), mean COP velocity (cm s-1) and COP area (cm2) were used to indirectly assess postural sway. The COP area (R 2 = 0.96), anteroposterior (R 2 = 0.85) and mediolateral (R 2 = 0.84) COP displacement increased linearly with additional load. The 20% load condition elicited the greatest increase in postural sway (d = 2.1-3.6) compared to 0%, while the 5% load had no effects on sway (P ≥ 0.05). In contrast, the mean COP velocity decreased by similar amounts when holding a load at 5% (d = 1.6), 10% (d = 1.4) and 20% (d = 1.5) body mass, compared to 0% (all P < 0.001). The slower COP velocity, combined with greater COP displacements may suggest that postural reactions were restricted and/or delayed. From a fall-prevention perspective, it is advised that older people avoid holding asymmetrical external loads greater than 5% of body mass.

Effect of cadence on locomotor-respiratory coupling during upper-body exercise.

INTRODUCTION: Asynchronous arm-cranking performed at high cadences elicits greater cardiorespiratory responses compared to low cadences. This has been attributed to increased postural demand and locomotor-respiratory coupling (LRC), and yet, this has not been empirically tested. This study aimed to assess the effects of cadence on cardiorespiratory responses and LRC during upper-body exercise. METHODS: Eight recreationally-active men performed arm-cranking exercise at moderate and severe intensities that were separated by 10 min of rest. At each intensity, participants exercised for 4 min at each of three cadences (50, 70, and 90 rev min-1) in a random order, with 4 min rest-periods applied in-between cadences. Exercise measures included LRC via whole- and half-integer ratios, cardiorespiratory function, perceptions of effort (RPE and dyspnoea), and diaphragm EMG using an oesophageal catheter. RESULTS: The prevalence of LRC during moderate exercise was highest at 70 vs. 50 rev min-1 (27 ± 10 vs. 13 ± 9%, p = 0.000) and during severe exercise at 90 vs. 50 rev min-1 (24 ± 7 vs. 18 ± 5%, p = 0.034), with a shorter inspiratory time and higher mean inspiratory flow (p < 0.05) at higher cadences. During moderate exercise, [Formula: see text] and f C were higher at 90 rev min-1 (p < 0.05) relative to 70 and 50 rev min-1 ([Formula: see text] 1.19 ± 0.25 vs. 1.05 ± 0.21 vs. 0.97 ± 0.24 L min-1; f C 116 ± 11 vs. 101 ± 13 vs. 101 ± 12 b min-1), with concomitantly elevated dyspnoea. There were no discernible cadence-mediated effects on diaphragm EMG. CONCLUSION: Participants engage in LRC to a greater extent at moderate-high cadences which, in turn, increase respiratory airflow. Cadence rate should be carefully considered when designing aerobic training programmes involving the upper-limbs.

The effects of a heat acclimation protocol in persons with spinal cord injury.

Persons without spinal cord injury (SCI) physiologically acclimate between seven to fourteen consecutive days of exercise in the heat. Decreased resting and exercise core temperature, decreased heart rate, increased plasma volume and increased thermal comfort during exercise are changes consistent with heat acclimation. Autonomic dysfunction after SCI impairs heat dissipation through sweating and vasodilation. The purpose of this study is to determine if seven consecutive days of exercise in the heat would result in physiologic changes consistent with heat acclimation in persons with SCI. Ten persons with SCI divided into two groups: tetraplegia (n=5) and paraplegia (n=5) exercised in 35°C using an arm ergometer at 50% Wpeak for 30min followed by 15min rest. This protocol was repeated over seven consecutive days. Heart rate (HR), skin temperature, aural temperature (Taur), rate of perceived exertion (RPE), rate of perceived thermal strain (RPTS), and plasma volume (PV) were measured throughout the protocol. There were no significant differences in resting Taur exercise Taur, mean skin temperature, HR, PV, RPE or RPTS over the 7 days for either the tetraplegic or paraplegic group. Participants with SCI did not demonstrate the ability to dissipate heat more efficiently over 7 days of exercise at 35°C. The lack of heat acclimation seen in persons with SCI has implications for the athlete and non-athlete alike. For the SCI athlete, inability to acclimate will impair performance and endurance especially in warm environments, compared to the person without SCI. For the SCI non-athlete, there is a greater risk of heat-related illness in warm environments that can negatively affect participation in outdoor activities and thus quality of life.

A comparison of two anaerobic test measurement systems using an upper body Wingate test.

This study aimed to compare performance measures acquired by two different Wingate Anaerobic Test systems; Cranlea and Monark. Twenty participants undertook 58 Wingate tests against a 4% body mass resistive load on a cycle ergometer adapted for arm cranking. Corrected peak power output (PP; W) was recorded using 1 rev min(-1), 0.5, 1 and 5 s averages and mean power output (MP; W). The Cranlea system recorded the greatest PP (589 ± 267 W) compared with the Monark (546 ± 267 W; P < 0.001). The PP using all other methods was also greater for the Cranlea compared with the Monark system (P < 0.001) with mean differences of 55 ± 18 W for 1 s averages and 22 ± 18 W for MP. Correlations between all PPs were strong (r = 0.99 - 0.97; P < 0.001). In conclusion, although the Cranlea system provides a consistently greater corrected PP it may not be enough to substantially differentiate between systems.

The effects of sodium bicarbonate (NaHCO3) ingestion on high intensity cycling capacity.

Ten healthy, non-cycling trained males (age: 21.2 ± 2.2 years, body mass: 75.9 ± 13.4 kg, height: 178 ± 6 cm, [Vdot]O2PEAK: 46 ± 10 ml · kg(-1) · min(-1)) performed a graded incremental exercise test, two familiarisation trials and six experimental trials. Experimental trials consisted of cycling to volitional exhaustion at 100%, 110% and 120% WPEAK, 60 min after ingesting either 0.3 g · kg(-1) body mass sodium bicarbonate (NaHCO3) or 0.1 g · kg(-1) body mass sodium chloride (placebo). NaHCO3 ingestion increased cycling capacity by 17% at 100% WPEAK (327 vs. 383 s; P = 0.02) although not at 110% WPEAK (249 vs. 254 s; P = 0.66) or 120% WPEAK (170 vs. 175 s; P = 0.60; placebo and NaHCO3 respectively). Heart rate (P = 0.02), blood lactate (P = 0.001), pH (P < 0.001), [HCO3 (-)], (P < 0.001), and base excess (P < 0.001) were greater in all NaHCO3 trials. NaHCO3 attenuated localised ratings of perceived exertion (RPEL) to a greater extent than placebo only at 100% WPEAK (P < 0.02). Ratings of abdominal discomfort and gut fullness were mild but higher for NaHCO3. NaHCO3 ingestion significantly improves continuous constant load cycling at 100% WPEAK due to, in part, attenuation of RPEL.

The effects of an increasing versus constant crank rate on peak physiological responses during incremental arm crank ergometry.

We examined the effects of concomitant increases in crank rate and power output on incremental arm crank ergometry. Ten healthy males undertook three incremental upper body exercise tests to volitional exhaustion. The first test determined peak minute power. The subsequent tests involved arm cranking at an initial workload of 40% peak minute power with further increases of 10% peak minute power every 2 min. One involved a constant crank rate of 70 rev · min(-1), the other an initial crank rate of 50 rev · min(-1) increasing by 10 rev · min(-1) every 2 min. Fingertip capillary blood samples were analysed for blood lactate at rest and exhaustion. Local (working muscles) and cardiorespiratory ratings of perceived exertion (RPE) were recorded at the end of each exercise stage. Heart rate and expired gas were monitored continuously. No differences were observed in peak physiological responses or peak minute power achieved during either protocol. Blood lactate concentration tended to be greater for the constant crank rate protocol (P = 0.06). Test duration was shorter for the increasing than for the constant crank rate protocol. The relationship between local RPE and heart rate differed between tests. The results of this study show that increasing cadence during incremental arm crank ergometry provides a valid assessment of peak responses over a shorter duration but alters the heart rate-local RPE relationship.

Impact of passive heat stress on persons with spinal cord injury: Implications for Olympic spectators.

Environmental heat stress can negatively impact health, work capacity, and athletic performance and potentially to lead to life-threatening consequences if not mitigated. With the upcoming Toyko Olympic games to be held during anticipated warm ambient temperatures (up to 29°C), and with spectators potentially spending long durations of time outdoors, certain populations of persons with impaired thermoregulatory capacity will be at higher risk of heat-related illness from passive heat stress. Persons with spinal cord injury (SCI) are one of these groups as a result of a decentralized sympathetic nervous system, which leaves them with impairment in convective and evaporative cooling via vasodilation and sweating, respectively. This review summarizes (1) thermoregulatory physiological responses of persons with SCI under passive heat stress: the effect of level and completeness of injury; (2) the impact of passive heat stress on quality of life (QOL), outdoor participation, behavioral thermoregulation, and cognition; (3) recommendations and education for clinicians providing health care for persons with SCI; and (4) suggestions of future directions for exploring the gaps in the literature on passive heat stress in persons with SCI. This article aims to equip consumers with SCI and health-care professionals with the most up-to-date knowledge on passive heat stress responses in persons with SCI, so that their attendance at the Olympic games can be done with maximal safety and enjoyment.

Thermoregulation following spinal cord injury.

Spinal cord injury results in physiologic adaptations affecting heat production (reduced muscle mass) and heat dissipation (blood redistribution and reduced sweating capacity below the level of lesion). However, it is the balance between these factors which determines whether heat balance is achieved. Core temperature estimates are generally consistent with those for the able-bodied, with cooler values reported in some instances. More notable differences are demonstrated through cooler lower-body skin temperatures at rest and a loss of anticipatory control during exposure to heat and cold when compared to the able-bodied. During exercise in cool conditions persons with paraplegia demonstrate similar body temperature responses as for the able-bodied but retain heat during recovery. Persons with tetraplegia demonstrate continual increases in core temperature and thus thermal imbalance along with greater heat retention. During exercise in the heat, athletes with paraplegia appear to be able to regulate body temperature to a similar extent as the able-bodied. Those with tetraplegia again show thermal imbalance but to a much greater extent than in the cold. Future work should focus upon specific sweating responses and adaptations following spinal cord injury, the effects of completeness of lesion, perceptual responses to environmental challenges, and how these translate to undertaking activities of daily living.

Evaluating the effects of caffeine and sodium bicarbonate, ingested individually or in combination, and a taste-matched placebo on high-intensity cycling capacity in healthy males.

This study evaluated the effects of ingesting sodium bicarbonate (NaHCO3) or caffeine individually or in combination on high-intensity cycling capacity. In a counterbalanced, crossover design, 13 healthy, noncycling trained males (age: 21 ± 3 years, height: 178 ± 6 cm, body mass: 76 ± 12 kg, peak power output (Wpeak): 230 ± 34 W, peak oxygen uptake: 46 ± 8 mL·kg(-1)·min(-1)) performed a graded incremental exercise test, 2 familiarisation trials, and 4 experimental trials. Trials consisted of cycling to volitional exhaustion at 100% Wpeak (TLIM) 60 min after ingesting a solution containing either (i) 0.3 g·kg(-1) body mass sodium bicarbonate (BIC), (ii) 5 mg·kg(-1) body mass caffeine plus 0.1 g·kg(-1) body mass sodium chloride (CAF), (iii) 0.3 g·kg(-1) body mass sodium bicarbonate plus 5 mg·kg(-1) body mass caffeine (BIC-CAF), or (iv) 0.1 g·kg(-1) body mass sodium chloride (PLA). Experimental solutions were administered double-blind. Pre-exercise, at the end of exercise, and 5-min postexercise blood pH, base excess, and bicarbonate ion concentration ([HCO3(-)]) were significantly elevated for BIC and BIC-CAF compared with CAF and PLA. TLIM (median; interquartile range) was significantly greater for CAF (399; 350-415 s; P = 0.039; r = 0.6) and BIC-CAF (367; 333-402 s; P = 0.028; r = 0.6) compared with BIC (313: 284-448 s) although not compared with PLA (358; 290-433 s; P = 0.249, r = 0.3 and P = 0.099 and r = 0.5, respectively). There were no differences between PLA and BIC (P = 0.196; r = 0.4) or between CAF and BIC-CAF (P = 0.753; r = 0.1). Relatively large inter- and intra-individual variation was observed when comparing treatments and therefore an individual approach to supplementation appears warranted.