Influence of strength and flexibility training, combined or isolated, on strength and flexibility gains

The aim of this study was to analyze the strength and flexibility gains after 12 weeks of strength and flexibility training (FLEX), isolated or combined. Twenty-eight trained women (age = 46 ± 6.52 years; body mass = 56.8 ± 5.02 kg; height = 162 ± 5.58 cm; mean ± SD) were randomly divided into 4 groups: strength training (ST) (n = 7), FLEX (n = 7), combination of strength and flexibility (ST + FLEX) (n = 7), and combination of flexibility and strength (FLEX + ST) (n = 7). All groups were assessed before and after training for the sit and reach test, goniometry, and 10 repetition maximum in bench press (BP) and leg press (LP) exercises. The training protocol for all groups included training sessions on alternate days and was composed of 8 exercises performed at periodized intensities. The FLEX consisted of dynamic stretching performed for a total duration of 60 minutes. The results demonstrated significant strength gains in all groups in the LP exercise (FLEX: p = 0.0187; ST: p = 0.0001; FLEX + ST: p = 0.0034; ST + FLEX: p = 0.0021). All groups except the FLEX improved in BP strength (FLEX: p = 0.1757; ST: p = 0.0001; FLEX + ST: p = 0.0017; ST + FLEX: p = 0.0035). Statistical analyses did not show significant differences between groups; however, effect sizes demonstrated slightly different treatment effects for each group. Largest treatment effects were calculated for the ST group (LP: 2.72; BP: 1.25) and the lowest effects in the FLEX group (LP: 0.41; BP: -0.06). Both combination groups demonstrated lower effect sizes for both LP and BP as compared with the ST group. No significant differences in flexibility were seen in any group, in any of the comparisons (p > 0.05). In conclusion, these findings suggest that combining strength and FLEX is not detrimental to flexibility development; however, combined training may slightly reduce strength development, with little influence of order in which these exercises are performed.