Reliability of jumping performance in active men and women under differentstretch loading conditions

Background. To determine the reliability of squatting jumps (SJ), counter-m ovement jumps (CMJ) and drop jumps (DJ) tests, as well as the reliability o f the optimal dropping height during drop jumping. Methods. Jumping performance was assessed in 8 male and 9 female physical e ducation students. Their age, weight and height ((x) over bar+/-SD) were 23 .9+/-2.1 years, 72.0+/-12.1 kg, 174.3+/-10.4 cm, and 23.1+/-2.0 years, 54.8 +/-4.9 kg, 160.1+/-5.0 cm for the males and females, respectively. The jump ing performance was determined on six different testing days. On each testi ng day, squatting jumps (SJ) and counter-movement jumps (CMJ) were performe d as well as drop jumps (DJ) from heights between 20 and 100 cm. The droppi ng height given the maximum attained height was registered as the optimal d ropping height (ODH). After a 15 min rest period, a 30 sec hopping test (HT ) was performed and the mean height attained (MHT) as well as the number of jumps executed (NHT) were recorded. The height attained was computed from the flight time, which was measured with a digital timer (+/-0.001 sec) con nected to a resistive platform. Results. The pooled coefficients of variation in percentage were 5.4 (SJ), 6.3 (CMJ), 6.2 (DJ), 31.9 (ODH), 3.1 (NHT) and 6.7 (MHT). A parabolic relat ionship between dropping height and attained height was found (r=0.39-0.43, p<0.001). The ODH was 48.2+/-14.0 cm and 62.9+/-21.3 cm for females and ma les, respectively (p<0.05). Multiple regression analysis showed than ODH ca n be predicted from the SJ with a standard error of 9 cm. Conclusions. The variability of the assessment of jumping performance is si milar to that reported for other variables used in the assessment of physic al fitness. In contrast, the assessment of the optimal dropping height is l ess reliable.