Effects of regular exercise and dual tasking on spatial and temporal parameters of obstacle negotiation in elderly women.

This study investigated the effects of regular exercise and dual tasking on bilateral spatial and temporal parameters of obstacle negotiation in elderly women. Sedentary (n=12) and physically active (n=12) elderly women volunteered to participate in this study. Gait kinematics were recorded during obstacle crossing when performing a dual task and when not performing a dual task. Physically active participants crossed obstacles more safely, in terms of clearance or distance to or over the obstacle, both with and without dual tasking, and usually for both lead and trail legs. Performing the dual task increased toe distance, and decreased heel distance and gait speed in the active participants, and increased toe clearance and heel distance, and decreased gait speed in the sedentary participants. Differences between preferred and non-preferred leg were accentuated for toe clearance in the lead limb. These results suggest that specialized exercises may not be needed for improvement in obstacle avoidance skills in the elderly, and participation in multi-activities, including aerobic exercises, may be sufficient.

Physical exercise prevents motor disorders and striatal oxidative imbalance after cerebral ischemia-reperfusion.

Stroke is the third most common cause of death worldwide, and most stroke survivors present some functional impairment. We assessed the striatal oxidative balance and motor alterations resulting from stroke in a rat model to investigate the neuroprotective role of physical exercise. Forty male Wistar rats were assigned to 4 groups: a) control, b) ischemia, c) physical exercise, and d) physical exercise and ischemia. Physical exercise was conducted using a treadmill for 8 weeks. Ischemia-reperfusion surgery involved transient bilateral occlusion of the common carotid arteries for 30 min. Neuromotor performance (open-field and rotarod performance tests) and pain sensitivity were evaluated beginning at 24 h after the surgery. Rats were euthanized and the corpora striata was removed for assay of reactive oxygen species, lipoperoxidation activity, and antioxidant markers. Ischemia-reperfusion caused changes in motor activity. The ischemia-induced alterations observed in the open-field test were fully reversed, and those observed in the rotarod test were partially reversed, by physical exercise. Pain sensitivity was similar among all groups. Levels of reactive oxygen species and lipoperoxidation increased after ischemia; physical exercise decreased reactive oxygen species levels. None of the treatments altered the levels of antioxidant markers. In summary, ischemia-reperfusion resulted in motor impairment and altered striatal oxidative balance in this animal model, but those changes were moderated by physical exercise.

Influence of a new bicycle crank design on aerobic parameters of non-cyclists.

AIM: A well known problem in conventional cycling crank systems is the pedalling dead spot when the crank arms are in vertical position. The pedalling dead spot mitigates the power output during the propulsion phase of pedalling. The aim of this study was to verify the effects of a new design of crank system on aerobic parameters of performance in healthy non-cyclists. The mechanical concept of the new system is based on the theory that crank arms should never be perpendicularly aligned to the ground at dead spot. METHODS: The maximal aerobic capacity (VO2 max) and different parameters of cycling efficiency were measured in 14 (mean±SD of age: 26±5) non-obese (body mass index: 26.0±3.0 kg/m2) healthy men in two different occasions at intervals of 2 days using alternately and in randomized order both the traditional crank system and the system without dead spot respectively. RESULTS: The workload performed was significantly higher with the new crank system as suggested by the higher exercise duration (12.89 ±2.36 vs. 13.33±2.30 min; P=0.032). CONCLUSION: The favourable results obtained in this study using the new chainring may be in consequence of a more efficient biomechanics of pedalling that does not reflect changes in O2 consumption and CO2 produced. However, it is not possible to exclude that involuntary motivational factors may have induced the difference in the time test since it was not possible to blind subjects about the two crank systems. Further investigations are necessary to confirm the results of this exploratory study and give a more exhaustive explanation about the mechanisms that allow the possible better performance with this new chainring system.

Effects of altering pedal frequency on the slow component of pulmonary VO2 kinetics and EMG activity.

This study investigated the effects of pedal frequency on the slow component of pulmonary oxygen uptake ( V O(2)) kinetics during heavy exercise at the same relative intensity. We hypothesized that higher pedal frequency (expected to enhance fast-twitch muscle fiber recruitment) would be associated with greater slow component amplitude (A' (s)), surface electromyography (normalized root mean square; RMS) and blood lactate concentration ([lactate]). Eight subjects performed square-wave transitions to heavy exercise at 35 and 115 rpm. Furthermore, alternated cadences square-wave transitions (35-115 rpm) were performed to examine the potential effects of additional fast-twitch muscle fiber recruitment on the slow component. Significance was accepted when P<0.05. The A' (s) was greater at higher cadences (0.58+/-0.08 and 0.70+/-0.09 L.min (-1) at 115 and 35-115 rpm, respectively) than at 35 rpm (0.35+/-0.04 L.min (-1)). Greater EMG increase over time (DeltaRMS ((10-3 min))) and [lactate] were observed at 115 and 35-115 rpm compared with 35 rpm. There was a significant correlation between A' (s) and overall DeltaRMS ((10-3 min)) for all pedal frequencies combined (r=0.63; P=0.001). Pedal frequency had no effect on time constants or time delays. These findings are consistent with the concept that progressive recruitment of muscle fibers is associated with the V O(2) slow component.

Cadence and workload effects on pedaling technique of well-trained cyclists.

This study investigated the effects of changing cadence and workload on pedaling technique. Eight cyclists were evaluated during an incremental maximal cycling and two 30-minute submaximal trials at 60% and 80% of maximal power output (W(60%) and W(80%), respectively). During submaximal 30-minute trials, they cycled for 10 minutes at a freely chosen cadence (FCC), 10 minutes at a cadence 20% above FCC (FCC+20%), and 10 minutes at a cadence 20% below FCC (FCC-20%). Pedal forces and kinematics were evaluated. The resultant force (RF), effective force (EF), index of effectiveness (IE) and IE during propulsive and recovery phase (IEprop and IErec, respectively) were computed. For W(60%), FCC-20% and FCC presented higher EFmean (69+/-9 N and 66+/-14 N, respectively) than FCC+20% (52+/-14 N). FCC presented the highest IEprop (81+/-4%) among the cadences (74+/-4 and 78+/-5% for FCC-20% and FCC+20%, respectively). For W(80%), FCC presented higher EFmean (81+/-5 N) than FCC+20% (72 +/- 10 N). The FCC-20% presented the lower IEprop (71+/-7%) among the cadences. The EFmin was higher for W(80%) than W(60%) for all cadences. The IE was higher at W (80%) (61+/-5%) than W (60%) (54+/-9%) for FCC+20% (all p<0.05). Lower cadences were more effective during the recovery phase for both intensities and FCC was the best technique during the propulsive phase.

Bilateral pedaling asymmetry during a simulated 40-km cycling time-trial.

AIM: This study investigated the pedaling asymmetry during a 40-km cycling time-trial (TT). METHODS: Six sub-elite competitive male cyclists pedaled a SRM Training Systems cycle ergometer throughout a simulated 40-km TT. A SRM scientific crank dynamometer was used to measure the bilateral crank torque (N.m) and pedaling cadence (rpm). All data were analyzed into 4 stages with equal length obtained according to total time. Comparisons between each stage of the 40-km TT were made by an analysis of variance (ANOVA). Dominant (DO) and non-dominant (ND) crank peak torque asymmetry was determined by the equation: asymmetry index (AI%)=[(DO-ND)/DO] 100. Pearson correlation analysis was performed to verify the relationship between exercise intensity, mean and crank peak torque. RESULTS: The crank peak torque was significantly (P<0.05) greater in the 4th stage compared with other stages. During the stages 2 and 3, was observed the AI% of 13.51% and 17.28%, respectively. Exercise intensity (%VO(2max)) was greater for stage 4 (P<0.05) and was highly correlated with mean and crank peak torque (r=0.97 and r=0.92, respectively) for each stage. CONCLUSIONS: The DO limb was always responsible for the larger crank peak torque. It was concluded that pedaling asymmetry is present during a simulated 40-km TT and an increase on crank torque output and exercise intensity elicits a reduction in pedaling asymmetry.