Effects of Arm-cranking Training with Electrical Muscle Stimulation on Vessel Function

This study aimed to determine whether arm-cranking training with electrical muscle stimulation (EMS) results in a greater improvement in vessel function than performing the same exercise without EMS. First, nine healthy young men performed two 20-min arm-cranking trials at 50% V˙O2max with and without EMS applied to the lower limbs. The flow-mediated vasodilation (FMD) of the right brachial artery was measured using a high-resolution ultrasound device. Both FMD and normalized FMD were increased significantly after the arm-cranking with EMS trial, and significant differences were observed between the two trials. Second, 16 healthy adult men were randomly assigned to either the arm-cranking exercise training (A) group or arm-cranking training with EMS (A+EMS) group. The subjects were engaged in 20 min of arm-cranking at 50% V˙O2max twice a week for 8 weeks with/without EMS applied to the lower limbs. The FMD increased significantly after A+EMS training session and the FMD in A+EMS group was significantly higher than that in the A group. These results indicate that acute/chronic endurance arm-cranking with EMS applied to the lower limbs improves the brachial artery endothelial function more markedly than the same exercise without EMS.

Specific and Holistic Predictors of Sprint Front Crawl Swimming Performance

The aim of the study was to examine the impact of selected water- and dry-land predictors of 50-m front crawl performance among 27 male swimmers aged 19.3 ± 2.67 years. The following water tests were performed: front crawl tethered arm stroking in a water flume (flow velocity: 0.9 m·s–1) and leg tethered flutter kicking in a swimming pool. Anaerobic tests on dry land included arm cranking and a set of 10 countermovement jumps. The maximal and average forces generated by legs in tethered swimming (Fl max and Fl ave) turned out to be the strongest predictors of sprint swimming aptitude. These values were strongly correlated with total speed (Vtotal50) (r = 0.49, p < 0.05 and r = 0.54, p < 0.01, respectively), start, turn, and finishing speed (VSTF) (r = 0.60, p < 0.01 and r = 0.67, p < 0.01, respectively). The relationship of Fl max and Fl ave with surface speed (Vsurface) was moderate (r = 0.33, non-significant and r = 0.41, p < 0.05, respectively). The maximal force generated by arms (Fa max) during flume tethered swimming significantly influenced Vsurface and Vtotal50 (0.51, p < 0.01 and 0.47, p < 0.05, respectively). Its relationship with VSTF was close to significant (0.36, p = 0.07). Upper and lower limb dry-land tests showed lower and more holistic relationships with the 50-m front crawl race, however, being a good complement to overall fitness assessment. Specific in-water evaluation, especially the newly prepared flutter kicking test, as well as dry-land tests, can be applied to regularly monitor progress in swimming training, and to identify talented swimmers.

The Effect of Crank Resistance on Arm Configuration and Muscle Activation Variances in Arm Cycling Movements

Arm cycling on an ergometer is common in sports training and rehabilitation protocols. The hand movement is constrained along a circular path, and the user is working against a resistance, maintaining a cadence. Even if the desired hand trajectory is given, there is the flexibility to choose patterns of joint coordination and muscle activation, given the kinematic redundancy of the upper limb. With changing external load, motor noise and changing joint stiffness may affect the pose of the arm even though the endpoint trajectory is unchanged. The objective of this study was to examine how the crank resistance influences the variances of joint configuration and muscle activation. Fifteen healthy participants performed arm cranking on an arm-cycle ergometer both unimanually and bimanually with a cadence of 60 rpm against three crank resistances. Joint configuration was represented in a 3-dimensional joint space defined by inter-segmental joint angles, while muscle activation in a 4-dimensional "muscle activation space" defined by EMGs of 4 arm muscles. Joint configuration variance in the course of arm cranking was not affected by crank resistance, whereas muscle activation variance was proportional to the square of muscle activation. The shape of the variance time profiles for both joint configuration and muscle activation was not affected by crank resistance. Contrary to the prevailing assumption that an increased motor noise would affect the variance of auxiliary movements, the influence of noise doesn’t appear at the joint configuration level even when the system is redundant. Our results suggest the separation of kinematic- and force-control, via mechanisms that are compensating for dynamic nonlinearities. Arm cranking may be suitable when the aim is to perform training under different load conditions, preserving stable and secure control of joint movements and muscle activations.

Motor Variances in Arm Cranking as a Function of the Resistance

Background: Arm cycling on an ergometer is common in sports training and rehabilitation protocols, but has not been widely studied from an aspect of neural control. The hand movement is constrained along a circular path, and the user is working against a resistance, maintaining a cadence. Even if the desired hand trajectory is given, there is the flexibility to choose patterns of joint coordination and muscle activation, given the kinematic redundancy of the upper limb. With changing external load, motor noise and changing joint stiffness may affect the pose of the arm even though the endpoint trajectory is unchanged, unless a control mechanism maintains the same arm configuration in corresponding time points of the cycles. However, the effect of crank resistance on the variances of arm configuration and muscle activation has not been investigated, yet. Methods: Fifteen healthy participants performed arm cranking on an arm-cycle ergometer both unimanually and bimanually with a cadence of 60 rpm against three crank resistances. We investigated arm configuration variances and muscle activation variances. Arm configuration was given by inter-segmental joint angles, while muscle activation by surface EMGs of arm muscles. Applying multifactorial ANOVA we evaluated the effects of resistance conditions. Results: Arm configuration variance in the course of arm cranking was not affected by crank resistance, while muscle activation variance was proportional to the square of electromyographic muscle activity. Furthermore, the shape of the variance time profiles for both arm configuration and muscle activation was not affected by crank resistance independently on cranking being performed unimanually or bimanually. Conclusions: Contrary to the prevailing assumption that an increased motor noise would affect the variance of auxiliary movements, the influence of noise doesn’t appear at the arm configuration level even when the system is redundant. Our results suggest that neural control stabilizes arm configurations against altered external force in arm cranking. This may reflect the separation of kinematic- and force-control, via mechanisms that are compensating for dynamic non-linearities. Arm cranking may be suitable when the aim is to perform training under different load conditions, preserving stable and secure control of joint movements and muscle activations.

Effect of Sildenafil Citrate on Exercise Capacity in Athletes With Spinal Cord Injury

Purpose: Ingestion of sildenafil citrate has performance-enhancing effects at high altitudes above 3800 m in able-bodied individuals. It is unknown whether it can improve the performance of athletes with spinal cord injury (SCI) at moderate altitudes (<2200 m), relevant to Paralympic competitions. As most men with SCI suffer from erectile dysfunction of neurologic origin and use sildenafil on a regular basis, it seems important to study the impact of sildenafil on exercise capacity. The outcome of this study is also relevant to the antidoping community. Methods: Twenty-seven healthy male wheelchair athletes with a motor-complete SCI participated in this prospective double-blind, randomized, placebo-controlled study. The participants performed arm cranking exercise to exhaustion at sea level and moderate altitude (2200 m) after ingestion of 50 mg sildenafil citrate or a placebo. Peak power output, peak oxygen uptake, peak heart rate, rating of perceived exertion, oxygen saturation, and lactate concentrations at exhaustion were measured. Results: Friedman analysis showed that peak power output at sea level was significantly higher (P = .004) under placebo treatment (median [minimum; maximum]: 120 W [35; 170]) compared with sildenafil (115 W [40; 165]). Blood oxygen saturation under sildenafil treatment at sea level (98% [81; 100]) was significantly higher (P = .006) compared with sildenafil treatment at moderate altitude (94% [85; 100]). All other parameters revealed no impact of sildenafil or altitude. Conclusions: In this study, the ingestion of sildenafil citrate in athletes with SCI demonstrated no positive effects on peak arm-cranking-exercise capacity compared with placebo either at sea level or at moderate altitude.