title: Reliability of jumping performance in active men and women under different stretch loading conditions.
abstract: BACKGROUND
  To determine the reliability of squatting jumps (SJ), counter-movement jumps (CMJ) and drop jumps (DJ) tests, as well as the reliability of the optimal dropping height during drop jumping.
  
  
  METHODS
  Jumping performance was assessed in 8 male and 9 female physical education students. Their age, weight and height (mean +/- 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 jumping performance was determined on six different testing days. On each testing day, squatting jumps (SJ) and counter-movement jumps (CMJ) were performed as well as drop jumps (DJ) from heights between 20 and 100 cm. The dropping height given the maximum attained height was registered as the optimal dropping 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) connected 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 relationship 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 males, respectively (p < 0.05). Multiple regression analysis showed than ODH can be predicted from the SJ with a standard error of 9 cm.
  
  
  CONCLUSIONS
  The variability of the assessment of jumping performance is similar to that reported for other variables used in the assessment of physical fitness. In contrast, the assessment of the optimal dropping height is less reliable.
authors.affiliation: Department of Physics, University of Las Palmas de Gran Canaria, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Arteaga
authors.forename: C
authors.initials: C
authors.lastname: Dorado
authors.forename: J
authors.initials: J
authors.lastname: Chavarren
authors.forename: J A
authors.initials: JA
authors.lastname: Calbet
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D010809:Physical Fitness; D012044:Regression Analysis; D015203:Reproducibility of Results