Effects of Unilateral versus Bilateral Complex Training and High Intensity Interval Training on the Development of Strength, Power and Athletic Performance

Aim: The purpose of the present study is to examine the effects of 6 weeks bilateral (BL) versus unilateral (UL) complex training combined with high intensity interval training (HIIT) on maximal strength, jumping ability, straight sprint (5, 10, 20 and 30 m), change of direction speed (CODS), repeated sprint ability (RSA) and specific endurance in Swedish elite male and female handball players. Another purpose was to examine if a bilateral deficit (BLD) exists in strength and jumping ability (power deficit) and if it changes differently with 6 weeks BL and UL complex training. Method: 18 male and 12 female elite handball players was selected to either a 6 weeks bilateral (BL, n = 10) or unilateral (UL, n = 20) complex strength training program. In addition both groups trained HIIT. Training volume, intensity and exercise motion was similar between the groups. Tests included maximal (1RM) UL and BL Smith machine squat strength, UL counter movement jump with arm swing (CMJ) and BL (CMJ), squat jump (SJ) jumping ability, modified T-test, straight sprint (5, 10, 20 and 30 m), repeated shuttle sprint ability (RSSA) and Yo-Yo Intermittent Recovery test (Yo-Yo IR) before and after 6 weeks training. Results: There was no significant difference between BL and UL groups and any of the selected tests. The UL group significantly (p < 0.05) increased sprint time preto post testing only between 0-10 m and significantly decreased RSAtotal preto post testing (p < 0.01). BL group significantly (p < 0.01) increased sprint time preto post testing only between 0-30 m. When pooling data from both groups significant (p < 0.01) improvements were seen in maximal UL and BL strength, UL CMJ dominant leg, CODS and Yo-Yo IR test as well as increasing the BLD and power deficit for elite male and female handball players. Conclusion: 6 weeks of complex training using only BL or UL exercises combined with HIIT resulted in no significant changes between groups in any of the selected tests. Training unilaterally could possibly be a safer training method since the absolute load is lesser than BL training.