DETERMINANTS OF THE THROWING VELOCITY IN HANDBALL -A STATISTICAL MODEL

INTRODUCTION The aim of the research was to find the influence of the basic anthropometrical and motor ability parameters on the ball velocity during throws in handball. These relationships seem to be very important for coaches, in order to improve the selection quality and the efficiency of training methods. The last task is particularly difficult among experienced players. METHODS Twelve high-performance handball field players took part in the experiment. The following somatic anthropometric indices were used: length, skeleton width, musculature and adiposity (28 parameters for each player). The average linear ball velocity was measured using a special photocell system. Muscle strength was evaluated on a special stand (locally made) under static conditions (flexors and extensors of elbow, shoulder, knee and hip joints and trunk). The speed-strength characteristics of the upper extremity were measured on the modified CES Ariel. Subjects performed simulated throws in the sitting position. The maximal and average mechanical power of the lower extremity and trunk was measured during the vertical CMJ performed on a force platform. The mean value (SD) was calculated for each parameter. A normality of distributions was examined using the Shapiro-Wilk test. At the next stage Pearson's correlation matrix and a multiple regression analysis were used (pe0.05). The raw data was recalculated to values in the T-scale and according to the Doolittle method the contribution to throwing velocity was calculated. The best regression subset was assigned using Fisher's discriminating method. The regression hyperplane parameters were estimated. RESULTS Expected values of the ball velocity (R=0.982; R~=o9.6 3): Y = 0.018 XI + 0.733 X2 + 0.039 Xg -0.332 Xq + 0.006 Xg - 2.854 where: X1 - max. angular velocity of the bar (36%), X2 - range of fingers (41%), X3 - average mechanical power in CMJ (3%), Xq - shoulder width (6%), Xg - isometric muscle strength of trunk flexors (1 1 %). After recalculation to T-values the final equation contains two main factors: anthropometric (A) and motor (M): y=0.017 A + 0.072 M + 10.571 (R=O 857) The proportional contribution of these factors in expected value of the ball velocity is 11.9% and 61.4%, respectively. The hyperplane parameters, which divides subjects into two groups according to throwing velocity criterion, are as follows: 0.149 M + 0,051 A - 23.821 = 0 CONCLUSIONS These results suggest that the most important throwing velocity determinant is the motor abilities level. Among analyzed parameters the strength of trunk flexors (abdominal muscles) and maximal arm (shoulder joint) angular velocity have a decisive effect on the ball velocity in handball. REFERENCES Atwater A.B. (1980) Exer. Spod Sci. Rev. 7:43-85. Bartlett L.R., Storey M.D., Sirnons B.D. (1 989) Am. J. Sports Med. 1 7: 89-91 . Eliasz J., Janiak J., Wit A. (1990): Sporf Wyczynowy 911 0: 17-23. Joris ti., Muijen Van A.E., lngen Schenau Van G.J., Kemper H.C.G. (1 985) J. Biom. 18:409-414. Muijen Van A.E., Jiiris H., Kemper H.C.G., lngen Schenau Van G.J. (1991). Sports Training, Med. Rehab. 2: 103-1 13

DETERMINANTS OF THE MAXIMAL MECHANICAL POWER DEVELOPED DURING THE COUNTERMOVEMENT JUMP (CMJ)

INTRODUCTION A countermovement (a preparatory movement in the direction opposite to that of the goal) increases performance in explosive movements such as the CMJ. The height of jump and the maximal power relative to body weight have been reported to be significantly correlated. Our previous observations has suggested the take-off technique (the countermovement depth) to affect power rather than height of jump. The purpose of the present study was to determine the influence of the height of jump, of the countermovement depth and of body mass on the maximal mechanical power developed during the positive take-off phase. METHODS Untrained students (56 female and 38 male) volunteered to take part in the CMJ jumping test consisting of 3 jumps performed with one-minute intervals on the computerized Kistler force plate. The subjects were requested to jump on the maximal height possible. Results of the highest jump were selected for each subject for further processing. The following variables were included into statistical analysis: the maximal mechanical power (PmaJ developed during the take-off, the height of jump (H), lowering of the body mass center before the take-off (L). and body mass (mb)' The Shapiro-Wilk test was used to examine the distributions of the tested variables. Pearson's correlation matrix and multiple regression analysis were employed to identity the parameters of the Pmax statistical model. Dolittle's method was used to estimate the contribution of the selected jump variables to the Pmax. RESULTS In both female and male groups the multiple regression procedure (the forward stepwise method) employed all the independent variables studied to construct the regressions equations. both of them proving very highly significant (

γ-Secretase inhibitor enhances antitumour effect of radiation in Notch-expressing lung cancer

BACKGROUND: Notch receptor has an important role in both development and cancer. We previously reported that inhibition of the Notch3 by γ-secretase inhibitor (GSI) induces apoptosis and suppresses tumour proliferation in non-small-cell lung cancer. Although radiation is reported to induce Notch activation, little is known about the relationship between radiation and Notch pathway. METHODS: We examined the effect of combining GSI and radiation at different dosing in three Notch expressing lung cancer cell lines. The cytotoxic effect of GSI and radiation was evaluated using MTT assay and clonogenic assay in vitro and xenograft models. Expressions of Notch pathway, mitogen-activated protein kinase (MAPK) pathway and Bcl-2 family proteins were investigated using western blot analysis. RESULTS: We discovered that the antitumour effect of combining GSI and radiation was dependent on treatment schedule. γ-Secretase inhibitor administration after radiation had the greatest growth inhibition of lung cancer in vitro and in vivo. We showed that the combination induced apoptosis of lung cancer cell lines through the regulation of MAPK and Bcl-2 family proteins. Furthermore, activation of Notch after radiation was ameliorated by GSI administration, suggesting that treatment with GSI prevents Notch-induced radiation resistance. CONCLUSION: Notch has an important role in lung cancer. Treatment with GSI after radiation can significantly enhance radiation-mediated tumour cytotoxicity