Valery Labarque

Oral creatine supplementation facilitates the rehabilitation of disuse atrophy and alters the expression of muscle myogenic factors in humans

1 We investigated the effect of oral creatine supplementation during leg immobilization and rehabilitation on muscle volume and function, and on myogenic transcription factor expression in human subjects. 2 A double‐blind trial was performed in young healthy volunteers (n=22). A cast was used to immobilize the right leg for 2 weeks. Thereafter the subjects participated in a knee‐extension rehabilitation programme (3 sessions week−1, 10 weeks). Half of the subjects received creatine monohydrate (CR; from 20 g down to 5 g daily), whilst the others ingested placebo (P; maltodextrin). 3 Before and after immobilization, and after 3 and 10 weeks of rehabilitation training, the cross‐sectional area (CSA) of the quadriceps muscle was assessed by NMR imaging. In addition, an isokinetic dynamometer was used to measure maximal knee‐extension power (Wmax), and needle biopsy samples taken from the vastus lateralis muscle were examined to asses expression of the myogenic transcription factors MyoD, myogenin, Myf5, and MRF4, and muscle fibre diameters. 4 Immobilization decreased quadriceps muscle CSA (∼10 %) and Wmax (∼25 %) by the same magnitude in both groups. During rehabilitation, CSA and Wmax recovered at a faster rate in CR than in P (P < 0.05 for both parameters). Immobilization changed myogenic factor protein expression in neither P nor CR. However, after rehabilitation myogenin protein expression was increased in P but not in CR (P < 0.05), whilst MRF4 protein expression was increased in CR but not in P (P < 0.05). In addition, the change in MRF4 expression was correlated with the change in mean muscle fibre diameter (r=0.73, P < 0.05). 5 It is concluded that oral creatine supplementation stimulates muscle hypertrophy during rehabilitative strength training. This effect may be mediated by a creatine‐induced change in MRF4 and myogenin expression.

The contribution of preschool playground factors in explaining children's physical activity during recess

BackgroundLow levels of physical activity are characteristic in preschoolers. To effectively promote physical activity, it is necessary to understand factors that influence young childrens physical activity. The present study aimed to investigate how physical activity levels are influenced by environmental factors during recess in preschool.MethodsPreschool playground observations and pedometry during recess were carried out in 39 randomly selected preschools (415 boys and 368 girls; 5.3 ± 0.4 years old). In order to examine the contribution of playground variables to physical activity levels, taking adjustment for clustering of subjects within preschools into account, multilevel analyses were conducted.ResultsDuring recess boys took significantly more steps per minute than girls (65 ± 36 versus 54 ± 28 steps/min). In both genders higher step counts per minute were significantly associated with less children per m2 and with shorter recess times. Only in boys a hard playground surface was a borderline significant predictor for higher physical activity levels. In girls higher step counts were associated with the presence of less supervising teachers. Playground markings, access to toys, the number of playing or aiming equipment pieces and the presence of vegetation or height differences were not significant physical activity predictors in both genders.ConclusionIn preschool children physical activity during outdoor play is associated with modifiable playground factors. Further study is recommended to evaluate if the provision of more play space, the promotion of continued activity by supervisors and the modification of playground characteristics can increase physical activity levels in preschoolers.

Promoting physical activity at the pre-school playground: The effects of providing markings and play equipment

OBJECTIVES We aimed to investigate the effects of providing play equipment and markings at the pre-school playground on physical activity engagement levels. METHODS We performed a cluster randomised control trial. In November and December 2007, a convenience sample of 40 public pre-schools in Flanders, Belgium, was randomly assigned to one of the following conditions: 1) in 10 pre-schools play equipment was provided, 2) in 10 pre-schools markings were painted on the playground, 3) in 10 schools play equipment was provided and markings were painted, 4) 10 schools served as a control condition. Accelerometer-based physical activity levels during recess were evaluated at baseline and 4 to 6 weeks after the implementation of the intervention in 583 children (52% boys; mean age 5.3 years, SD 0.4). RESULTS At baseline pre-schoolers spent only 11.2% (average: 4.7 min) of recess time in moderate to vigorous activity, while 61.3% (average: 25.7 min) was spent in sedentary activity. The interventions were not effective in increasing the average activity levels or the percentages of engagement in moderate or vigorous activity, or in decreasing sedentary time. CONCLUSION Providing playground markings or play equipment is not sufficient to increase activity levels and decrease levels of sedentary activity during pre-school recess. More activating supervision and the inclusion of more structured physical activity seem needed.

Resistance training alters torque-velocity relation of elbow flexors in elderly men.

PURPOSE The aim of the study was to compare in vivo dynamic muscle characteristics (torque-velocity relation and maximal contraction velocity) of sedentary young subjects with elderly men before and after training. METHODS Elbow flexion maximal isometric (Tmax) and dynamic torque at velocities between 100 degrees.s-1 and 600 degrees.s-1 were measured, from which maximal contraction velocity was estimated (eVmax). These parameters were obtained from 18 young sedentary subjects (Y) and from 23 healthy sedentary elderly (mean age 63 yr) men (E) before (PRE), after 13 wk (MID), and 26 wk (POST) of moderate intensity resistance training (30RM) of the elbow flexor muscles. RESULTS Y and E before training had similar Tmax, but mean dynamic torque over all velocities was 49.1% higher in Y compared with E. After 13 wk of training TmaxE increased by 8.2% and mean dynamic torque increased by 61.2%, with a velocity dependent gain. For eVmaxE an increase of 21.8% was observed. The second 13-wk training period did not induce further increases. CONCLUSION The results of the present study demonstrate that, after moderate intensity resistance training of healthy elderly men, maximal contraction velocity of elbow flexors (eVmax), estimated from the torque-velocity curve, increased to values observed for sedentary young men.