Effects of two stretching techniques on vertical jump performance of young basketball players

Aim: Leg explosive force, evaluated by tests based on vertical jumps, is crucial in many sports. Although stretching exercises are supposed to enhance it, recent studies have found decreases of athletic task performances preceded by stretching exercises. We investigated if two different types of stretching affect the vertical jump performance of ten basketball players. Method: Ten female basketball players (13.2 ± 0.4 years) performed in 3 different days: (1) 5 min of light jogging; (2) a randomized sequence of 8 squat jumps (SJ) and 8 counter movement jumps (CMJ); (3) test condition: rest in day 1 (control, CC), active stretching (AS) in day 2, dynamic stretching (DS) in day 3; (4) 8 SJ and 8 CMJ. AS consisted of 3 series of 15 s static bilateral stretching exercises for the hamstrings, quadriceps, and triceps surae muscles. In DS the subjects bobbed for 30 s each muscle. The height (hf) and the average power (Pavg) of the jumps were measured by a QuattroJump force platform (Kistler, Switzerland). A 3-way ANOVA test (jump type, test condition, pre-post condition) was performed. When appropriate a Bonferroni post hoc test was run. Results: No differences of hf were found in types of jump and in test condition. The pre- and post-condition hf values were different (p = 0.008). The interaction between test condition and pre- and post- condition was different (p = 0.03). No differences were found between hf values of pre- and post-condition of CC. For both AS and DS hf value of the pre- was higher than that of the post- condition (p = 0.01 and p = 0.003). Pavg of SJ was lower than that of CMJ (p \ 0.005). Pavg of pre- was different than that of the post-condition (p \ 0.0005). The interaction between test condition and pre- and post- condition was different (p = 0.04). No differences were found between Pavg values of pre- and post-condition of CC. For both AS and DS Pavg value of pre- was higher than that of post-condition (p = 0.02 and p = 0.002). Conclusions: The stretching techniques considered have detrimental effects on vertical jump performance. This could be due to changes in musculotendinous stiffness occurred after the stretching tasks.