Muscular responses during motor imagery as a function of muscle contraction types.

This study was designed to gain more insight into the mechanisms underlying motor imagery (MI). While there is ample evidence that motor performance and MI share common central neural mechanisms, the question whether MI is accompanied by subliminal electromyographic (EMG) activity remained unsolved. Thirty right-handed volunteers were asked to lift or to imagine lifting a weighted dumbbell using different types of muscle contraction, i.e. heavy concentric, light concentric, isometric and eccentric contractions. EMG activity from 9 muscles of the dominant arm (agonist, antagonist, synergist and fixator muscles) was monitored. Autonomic nervous system responses were also recorded on the non-dominant hand, thus attesting mental activity at the peripheral level. A significant increased pattern of EMG activity was recorded in all muscles during MI, when compared to the rest condition, while the goniometric data did not reveal any movement. Although being subliminal, the magnitude of this activation was found to be correlated to the mental effort required to lift a weight mentally, as more EMG activity was recorded during imaginary lifting of heavy than light concentric contractions. When considering the different types of contraction, our results provided evidence of selective changes in EMG activity. Especially, the imagined eccentric condition elicited a significant weaker muscular activity than all other conditions. In addition, the changes in the EMG pattern mirrored those usually observed during physical movement. These findings support the hypotheses of a selective effect of MI at the level of muscular activity and of incomplete inhibition of the motor command during MI.

Eating attitudes, body esteem, perfectionism and anxiety of judo athletes and nonathletes.

The aim of the study was to examine the prevalence and relationships between disordered eating, menstrual irregularity, musculoskeletal injuries and psychological characteristics in 24 judo athletes (12 females and 12 males) and 31 controls (14 females and 17 males). All these parameters were assessed by a health/medical, dieting and menstrual history questionnaire, the Eating Attitudes Test (EAT-26), the Multidimensional perfectionism scale, the Rosenberg Self-esteem, the Body esteem scale, and the Profile of Mood States. Body mass index (BMI) was also computed. Twenty-five percent of female athletes would be "at risk" of EDs (EAT-26 > 20) and 0 % in the other sample groups. Bone injuries sustained over the judo athlete career were reported by 25 % of females and 33.3 % of males, while 35.7 % of the female controls reported bone injuries. The total frequency of menstrual dysfunction among judo athletes was 58.3 %, while 7.1 % of female controls reported oligoamenorrhea. Regression analyses showed that BE-Weight Satisfaction and BMI contributed to 54.6 % and 17 % of the variance, respectively, in the prediction of log-transformed Global EAT scores among female judo athletes. These data indicate that while the prevalence of clinical eating disorders is low in judo athletes, many are "at risk" for an eating disorder, which places them at an increased risk for menstrual irregularity and bone injuries. This study also highlights the relevance of body esteem to eating disorder symptoms.

Fixed versus free-floating stretcher mechanism in rowing ergometers: mechanical aspects.

The mechanical responses (i.e. external contact forces and external power) of 25 elite rowers to a race-pace rowing protocol were investigated on the traditional fixed stretcher mechanism and the more recently introduced free-floating stretcher mechanism rowing ergometers. Using a Rowperfect rowing ergometer for both conditions, external contact forces at the handle, stretcher and sliding seat, as well as the displacements of the handle and stretcher, were recorded. The external power was calculated as the product of the force and velocity data from both the handle and stretcher. Significant differences (P < 0.05) between the two conditions for each mechanical parameter were observed. The fixed condition showed larger maximum values for forces and external power and average power throughout the rowing cycle. Moreover, rowing with the fixed mechanism generated higher inertial forces during the transition between the propulsion and recovery phases, especially at the catch of the cycle. The results suggest that: (i) muscular coordination may differ according to the stretcher mechanism used, which could have an impact on the physiological adaptations of muscles; and (ii) the free-floating mechanism may induce lower catch and maximum values for net joint forces and net joint moments that could decrease the risk of injury.