With every athlete I work with hear the same concern: “If I add muscle will I lose flexibility?” Often I reply with a stern long winded answer, about different types of muscle contractions, but most would prefer a simple “No”. For those who want a more detailed answer, this recent study is for you!

Despite popular belief, strength training promotes flexibility gains. However, most people seeking flexibility gains aren’t only performing strength training, they are often performing combined strength and flexibility training.
Luckily a study by Leite (2014) looked at four different types of training and it’s effects of flexibility after 12 weeks for a minimum of 44 sessions:

Strength training: Eight exercises performed in three sets per exercise with periodized training. The first month between 8 – 12 repetitions, the next month between 6 – 10 repetitions, and the last month between 10 – 15 repetitions. The exercises were: leg press, leg extension, leg curl, bench press, font lat pulldown, seated shoulder press, biceps curl, and triceps pulley. Flexibility training: Dynamic stretching was performed for 60 minutes, 30 repetitions in each set. All stretching were performed to mild discomfort. Combination of strength and flexibility training: Both groups, with the strength training before the flexibility training. Combination of flexibility and strength training: Both groups, with the flexibility before the strength training.

All groups significantly improved strength in the leg press. The bench press improved significantly in all groups except the flexibility group. In fact, the flexibility group showed a decrease in bench press strength.
For flexibility, there was no significant change in the sit-and-reach test between groups. Also, no groups significantly improved flexibility, even the flexibility group.
Overall, the addition of dynamic flexibility does not impair strength gains when performed before or after strength training. Also, strength training does not have a negative effect on flexibility gains. However, there were no improvements in flexibility in any groups, questioning the effectiveness of the flexibility program.

Strength and conditioning programs must reflect the goal of the individual. At COR, we have monthly goal setting and evaluations, helping determine if the plan is on course or if rerouting is required. If your goal is improving strength, it’s paramount to add strength training. If you are seeking improvements in range of motion, strength training should not inhibit these gains. In fact, most strength programs, should improve the range of motion you are moving through. For example, if you want hamstrings range of motion improvement, the deadlift and other hip hinge exercises should enhance this range. If you are looking for more hip flexion range of motion, a deep squat or snatch (see picture above) will improve this as well. The last caveat, more range of motion doesn’t always matter. If you are seeking range of motion improvements, have a purpose for this improved range, ideally functional (improving sport or life).

Reference:

Leite T, de Souza Teixeira A, Saavedra F, Leite RD, Rhea MR, Simão R INFLUENCE OF STRENGTH AND FLEXIBILITY TRAINING, COMBINED OR ISOLATED, ON STRENGTH AND FLEXIBILITY GAINS.J Strength Cond Res. 2014 Sep 29. [Epub ahead of print]

Written by G. John Mullen, DPT, CSCS