You have heard that stretching can improve flexibility and balance, but increase strength? It can for novice weight lifters according to research conducted by Dr. Joke Kokkonen, professor in the Exercise and Sport Science Department at Brigham Young University-Hawaii.  Dr. Kokkonen and colleagues compared the effects of a combined program of weight training and static stretching to weight training alone on lower-body strength.  Because previous research has shown that stretching activities have been associated with increases in muscle size, Dr. Kokkonen's research team wanted to investigate if a combined training program would have an additive effect, thus resulting in greater strength gains.

The subjects included 32 college-age students (16 women and 16 men) who were matched into pairs based on gender and lower body strength as measured by a knee extension 1 repetition maximum test (i.e., the maximum amount of weight that can be lifted 1 time).  The subjects that were chosen were either physically inactive or did not exercise more than twice per week. One person from each pair was randomly assigned to one of two testing conditions: weight training and static stretching combined or weight training alone. 

The weight training activities for both groups included 3 sets of 6 repetitions for knee extension, knee flexion, and leg press exercises performed 3 days per week for a total of 8 weeks.  Weight load was increased each week.  Those who were in the combined weight training and stretching group performed static stretching activities for 30 minutes at a time twice a week on non-weight training days.  The muscle groups stretched included the quadriceps, hamstrings, hip external and internal rotators, hip adductors and abductors, dorsiflexors and plantarflexors.  Each stretch was performed 3 times and held for 15 seconds followed by a 15-second rest interval.

At the end of the eight weeks, both groups had experienced gains in strength.  However, those in the combined strength training and stretching group showed significantly greater increases in their 1 repetition maximum tests for knee extension, knee flexion, and leg press.  Furthermore, subjects who also performed stretching activities were able to increase workload to a greater degree each week than those who did not stretch.

The investigators conclude that for novice weight trainers who wish to maximize their strength gains, adding a stretching program on nonweight training days can offer some benefit.

Note:  Before beginning an exercise program or increasing the intensity level of a current routine, a physician's approval should be obtained, especially for older adults and those at risk for or who currently have chronic health conditions.

Resource
The Journal of Strength and Conditioning Research; February 2010; pp. 502-506; "Early-Phase Resistance Training Strength Gains in Novice Lifters are Enhanced by Doing Static Stretching"; Kokkonen, J. et al.,.