Force variability during isometric wrist flexion in highly skilled and sedentary individuals.

The association of expertness in specific motor activities with a higher ability to sustain a constant application of force, regardless of muscle length, has been hypothesized. Ten highly skilled (HS group) young tennis and handball athletes and 10 sedentary (S group) individuals performed maximal and submaximal (5, 10, 20, 50, and 75% of the MVC) isometric wrist flexions on an isokinetic dynamometer (Kin-Com, Chattanooga). The wrist joint was fixed at five different angles (230, 210, 180, 150, and 1300). For each position the percentages of the maximal isometric force were calculated and participants were asked to maintain the respective force level for 5 s. Electromyographic (EMG) activation of the Flexor Carpi Ulnaris and Extensor Digitorum muscles was recorded using bipolar surface electrodes. No significant differences were observed in maximal isometric strength between HS and S groups. Participants of HS group showed significantly (P < 0.05) smaller force coefficient of variability (CV) and SD values at all submaximal levels of MVC at all wrist angles. The CV and SD values remained unaltered regardless of wrist angle. No difference in normalized agonist and antagonist EMG activity was observed between the two groups. It is concluded that long-term practice could be associated with decreased isometric force variability independently from muscular length and coactivation of the antagonist muscles.

Muscular strength and jumping performance after handball training versus physical education program for pre-adolescent children.

The purpose was to compare a 6-mo. specific handball training program and a typical physical education program on various strength and jumping skills. The participants (M age= 13.7 yr., SD= 1.5) were divided into the Handball Group (n=51) and the Physical Education Group (n=70). The latter performed 3 sessions/ week (60 min.) including ball-handling drills, horizontal and vertical jump shots, fast break, and several defensive skills. The former performed the program provided by the Ministry of Education including track and field and other team sport drills. Analyses of covariance showed that the handball group displayed greater improvement in explosive strength of upper limbs, jumping performance, maximum isometric force of right grip, and 10-m running velocity. Handball training can significantly improve pre-adolescent performance with upper and lower limbs. Inclusion of specific handball drills in the physical education program is recommended.