Influence of Strength and Flexibility Training, Combined or Isolated, on Strength and Flexibility Gains

Abstract: The aim of this study was to analyze the strength and flexibility gains after 12 weeks of strength and flexibility training, isolated or combined. Twenty-eight trained women (mean +/- SD age = 46 +/- 6.52 years; body mass = 56.8 +/- 5.02 kg; height = 162 +/- 5.58 cm) were randomly divided into four groups: strength training (ST) (n = 7), flexibility training (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 pre- and post-training for the Sit-and-Reach test, goniometry, and ten repetition maximum (10RM) in bench press and leg press exercises. The training protocol for all groups included training sessions on alternate days, and was composed of eight exercises performed at periodized intensities. The flexibility training consisted of dynamic stretching performed for a total duration of 60 minutes. The results demonstrated significant strength gains in all groups in the leg press 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 bench press 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 (Leg press: 2.72; bench press: 1.25) and the lowest effects in the FLEX group (leg press: .41; bench press: -.06). Both combination groups demonstrated lower effect sizes for both leg press and bench press as compared to 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 flexibility training 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.


Alex’s Notes: Stretching and strength training really go hand in hand to promote overall fitness. However, it has been suggested that long stretches before lifting heavy things can impair performance. But as the current authors point out, “there are no studies in the literature that compared the chronic responses of different combinations of these trainings using dynamic stretching” and “most studies have a sedentary sample.” The current investigation thus uses a novel approach to assess how flexibility and strength interact with one another by focusing on dynamic stretching and experienced lifters.

“28 women experienced in strength and flexibility training were randomly divided into four groups: strength training (ST) (n = 7), flexibility training (FLEX) (n = 7), combination of strength and flexibility (ST + FLEX) (n = 7), and combination of flexibility and strength (FLEX + ST) (n = 7).”

A 10RM test for bench press (BP) and leg press (LP) was performed at baseline and after 12-weeks of training, and flexibility was assessed through the Sit and Reach Test and goniometry measurements whereby shoulder, elbow, hip, knee, and trunk movements were taken to the point of mild discomfort or anatomical limitation.

The strength training sessions were performed on alternating days and consisted of 3 sets of 8-12RM (month 1), 6-10RM (month 2), and 10-15RM (month 3) of the following exercises: leg press, leg extension, leg curl, bench press, front lat pulldown, seated shoulder press, biceps curl, and triceps pulley. Rest intervals were one minute long. The flexibility training sessions consisted of three sets of 30 reps per set for dynamic stretching exercises “very similar” to the test exercises for both the lower and upper body. No rest was provided between exercises but the stretched muscle group was changed, and the total session was one hour long. The combined training sessions consisted of both with one or the other coming first.






Bench Press

Moderate Gain

Trivial Loss

Moderate Gain

Moderate Gain

Leg Press

Large Gain

Small Gain

Small Gain

Moderate Gain

Sit & Reach

Trivial Gains


Small Gains

What becomes apparent when looking to the results in the table above is that strength training does not have any negative impact on flexibility and in fact may improve flexibility in a manner similar to that of dynamic stretching. However, there may be a slight reduction in strength development with the addition of flexibility training.

The two points of emphasis on this study is that the population was experienced women lifters, and the stretching was dynamic in nature. Thus, it remains to be seen how short-term static stretching would influence both strength and flexibility in the long-term. By short-term, I mean less than 30 seconds, which the previously hyperlinked review suggested was the cut-off point for strength inhibition.

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