Methodological Considerations on the Relationship Between the 1,500-m Rowing Ergometer Performance and Vertical Jump in National-Level Adolescent Rowers.

Maciejewski, H, Rahmani, A, Chorin, F, Lardy, J, Samozino, P, and Ratel, S. Methodological considerations on the relationship between the 1,500-m rowing ergometer performance and vertical jump in national-level adolescent rowers. J Strength Cond Res 33(11): 3000-3007, 2019-The purpose of this study was to investigate whether 3 different approaches for evaluating squat jump performance were correlated with rowing ergometer performance in elite adolescent rowers. Fourteen young male competitive rowers (15.3 ± 0.6 years), who took part in the French rowing national championships, performed a 1,500-m all-out rowing ergometer performance (P1500) and a squat jump (SJ) test. The performance in SJ was determined by calculating the jump height (HSJ in cm), a jump index (ISJ = HSJ·body mass·gravity, in J), and the mean power output (PSJ in W) from the Samozino et al.'s method. Furthermore, allometric modeling procedures were used to consider the importance of body mass (BM) in the relationships between P1500 and jump scores. P1500 was significantly correlated with HSJ (r = 0.29, p ≤ 0.05), ISJ (r = 0.72, p < 0.0001), and PSJ (r = 0.86, p < 0.0001). Furthermore, BM explained at least 96% of the relationships between SJ and rowing performances. However, the similarity between both allometric exponents for PSJ and P1500 (1.15 and 1.04, respectively) indicates that BM could influence jump and rowing ergometer performances at the same rate, and that PSJ could be the best correlate of P1500. Therefore, the calculation of power seems to be more relevant than HSJ and ISJ to (a) evaluate jump performance and (b) infer the capacity of adolescent rowers to perform 1,500-m all-out rowing ergometer performance, irrespective of their body mass. This could help coaches to improve their training program and potentially identify talented young rowers.

Changes in Motor Coordination Induced by Local Fatigue during a Sprint Cycling Task.

PURPOSE: This study investigated how muscle coordination is adjusted in response to a decrease in the force-generating capacity of one muscle group during a sprint cycling task. METHODS: Fifteen participants were tested during a sprint before and after a fatigue electromyostimulation protocol was conducted on the quadriceps of one leg. Motor coordination was assessed by measuring myoelectrical activity, pedal force, and joint power. RESULTS: The decrease in force-generating capacity of the quadriceps (-28.0% ± 6.8%) resulted in a decrease in positive knee extension power during the pedaling task (-34.4 ± 30.6 W; P = 0.001). The activity of the main nonfatigued synergist and antagonist muscles (triceps surae, gluteus maximus and hamstrings) of the ipsilateral leg decreased, leading to a decrease in joint power at the hip (-30.1 ± 37.8 W; P = 0.008) and ankle (-20.8 ± 18.7 W; P = 0.001). However, both the net power around the knee and the ability to effectively orientate the pedal force were maintained during the extension by reducing the coactivation and the associated negative power produced by the hamstrings. Adaptations also occurred in flexion phases in both legs, exhibiting an increased power (+17.9 ± 28.3 [P = 0.004] and +19.5 ± 21.9 W [P = 0.026]), associated with an improvement in mechanical effectiveness. CONCLUSION: These results demonstrate that the nervous system readily adapts coordination in response to peripheral fatigue by (i) decreasing the activation of adjacent nonfatigued muscles to maintain an effective pedal force orientation (despite reducing pedal power) and (ii) increasing the neural drive to muscles involved in the flexion phases such that the decrease in total pedal power is limited.

Relationship between Force-Velocity Profiles and 1,500-m Ergometer Performance in Young Rowers.

Rowing races require developing high level of force and power output at high contraction velocity. This study determined the force-velocity and power-velocity (F-P-V) profiles of lower and upper limbs of adolescent rowers and their relationships with a 1,500-m rowing ergometer performance. The power developed during the 1,500-m (P1500) was evaluated in fourteen national-level male rowers (age: 15.3±0.6 yrs). F-P-V profiles were assessed during bench pull (BP) and squat jump (SJ) exercises. The theoretical maximal values of force (F0), velocity (V0), power output (Pmax) and the F-V relationship slope (S FV ) were determined. The body mass (BM) influence on these relationships was considered using an allometric approach. F0 was 720±144 and 2146±405 N, V0 was 1.8±0.1 and 1.8±0.3 m·s-1, Pmax was 333±83 and 968±204 W and SFV was -391±54 and -1,200±260 N·s·m-1 for BP and SJ, respectively. Upper and lower limb F0 and Pmax were significantly related. P1500 was significantly (P<0.05) correlated to V0-BP, F0-BP, SFV-BP, Pmax-BP, F0-SJ and Pmax-SJ (r²=0.29 to 0.79). BM accounted for more than 90% of these relationships. Rowers' F-P-V profiles reflect adaptations to chronic rowing practice. F-P-V profiles and rowing performance correlations suggest that BP and SJ exercises are relevant to evaluate young rowers' explosive abilities.

Interpersonal Coordination and Individual Organization Combined with Shared Phenomenological Experience in Rowing Performance: Two Case Studies.

The principal aim of this study was to examine the impact of variability in interpersonal coordination and individual organization on rowing performance. The second aim was to analyze crew phenomenology in order to understand how rowers experience their joint actions when coping with constraints emerging from the race. We conducted a descriptive and exploratory study of two coxless pair crews during a 3000-m rowing race against the clock. As the investigation was performed in an ecological context, we postulated that our understanding of the behavioral dynamics of interpersonal coordination and individual organization and the variability in performance would be enriched through the analysis of crew phenomenology. The behavioral dynamics of individual organization were assessed at kinematic and kinetic levels, and interpersonal coordination was examined by computing the relative phase between oar angles and oar forces and the difference in the oar force impulse of the two rowers. The inter-cycle variability of the behavioral dynamics of one international and one national crew was evaluated by computing the root mean square and the Cauchy index. Inter-cycle variability was considered significantly high when the behavioral and performance data for each cycle were outside of the confidence interval. Crew phenomenology was characterized on the basis of self-confrontation interviews and the rowers' concerns were then analyzed according to course-of-action methodology to identify the shared experiences. Our findings showed that greater behavioral variability could be either "perturbing" or "functional" depending on its impact on performance (boat velocity); the rowers experienced it as sometimes meaningful and sometimes meaningless; and their experiences were similar or diverging. By combining phenomenological and behavioral data, we explain how constraints not manipulated by an experimenter but emerging from the ecological context of a race can be associated with functional adaptations or perturbations of the interpersonal coordination.

The 1,500-m Rowing Performance is Highly Dependent on Modified Wingate Anaerobic Test Performance in National-Level Adolescent Rowers.

PURPOSE: The aim of the current study was to determine whether the anaerobic performance assessed by a modified Wingate test could account for the 1,500-m rowing ergometer performance in young competitive rowers. METHODS: Fourteen national-level adolescent rowers performed on a rowing ergometer i) a 30-s allout exercise (i.e., modified Wingate test) and ii) a 1,500-m all-out exercise (i.e., rowing performance). For each of these two exercises, the mean power output was considered as the main performance criterion (PWIN and P1500, respectively). RESULTS: PWIN was correlated to P1500 (r2 = .83, p < .0001, ß = 100%). Furthermore, the estimated total muscle mass was correlated to PWIN and P1500 (r2 = .72 and r2 = .83, p < .0001, ß = 100%, respectively). The allometric scaling also indicated that total muscle mass accounts 62% for the relationship between PWIN and P1500. CONCLUSION: Our results highlight the importance of considering the contribution of total muscle mass and anaerobic energy pathways to 1,500-m rowing performance in competitive adolescent rowers. Therefore, the modified Wingate test could be used by rowing coaches to potentially identify talented young rowers.

The effect of hemodialysis session on postural strategies in older end-stage renal disease patients.

Patients suffering from end-stage renal disease experience multiple disabilities, such as muscle wasting, weakness, higher postural sway, and fall rates compared with healthy population, which has a negative effect on physical functioning and autonomy. The vital treatment of hemodialysis is recognized to induce important post-hemodialysis fatigue, hypotension, cramps, and headache due to the rapid fluid redistribution, among others. Nevertheless, even the well-known negative effect of aforementioned consequences of hemodialysis treatment, its effect on physical function, especially postural balance, is unclear. Thus, this study hypothesized the adverse effect of hemodialysis treatment on postural sway in 12 end-stage renal disease patients (mean age 63.3 ± 11 years) through the analysis of center-of-pressure (COP) trajectories recorded before and immediately after hemodialysis session. Evident postural alterations were observed at post-hemodialysis balance assessment for COP position-based (Fs < 7.7, P < 0.02) and COP velocity-based variables (Fs > 2.33, P < 0.05), without changes in complexity of COP time series in anteroposterior and mediolateral directions. These results suggest that period after hemodialysis treatment is particularly unsafe, as evidenced by important disability in postural control, and highlight the importance of the medical support and falls-related prevention strategies of these older frail patients after hemodialysis treatment.

Effects of rotation amplitude on arm movement when rotating a spherical object.

Arm movements when rotating a spherical object were experimentally investigated. Twelve volunteers participated in the experiment and were asked to rotate a sphere for a large range of amplitude. Results showed that subjects anticipated their posture at the beginning of object manipulation even for low rotation amplitudes. The way of anticipation strongly depended on rotation direction. The end-state comfort hypothesis, effects of joint limits and principle of minimum work were examined for explaining motion control. The anticipation would ensure a better end-state comfort while avoiding joint limits in case of higher amplitude of object rotation. Meanwhile, it should not deteriorate the comfort at the beginning of manipulation too much. High postural variability for low rotation amplitude tasks suggested that there might exist a range of postures of similar level of comfort. These findings will be useful in developing human behaviour-based motion simulations for digital human. PRACTITIONER SUMMARY: Arm movement was investigated when rotating a spherical object with a large range of amplitude. The end-state comfort hypothesis, effects of joint limits and principle of minimum work were examined for explaining motion control. Results will be helpful for a better design of rotary controls and for developing motion simulation algorithms.