Effects of stretching on strength training
(09-10-2013) Stretching is often performed 
before or during a workout to increase mobility, reduce risk of injury and to warm up the muscles. Although previous research has indicated that static stretching beforehand does not reduce injury rate or warm up the muscles, researchers were interested in the longer term effects of stretching on strength training effects which were unknown until now.
What did the researchers do?
The researchers recruited 30 volunteers with strength training experience who were randomly divided into three groups. To determine the effects of stretching on strength training, one group performed static stretching before strength training. One group performed static stretching between strength training exercises. And one group only performed the strength training without any form of stretching. The subjects were tested on their 8 repetition maximum in the Bench Press, Lat Pulldown, Leg Extension and Leg Curl exercises. These tests were done before and after a 10 week strength training program.
The strength training program consisted of 8 exercises, among which the tested exercises and in addition the triceps extension, biceps curl, trunk extension and trunk flexion exercises. Each exercise was performed for 4 sets at weights that corresponded with 8-10 repetitions per set. All subjects trained 3 times a week for the duration of the program.
What were the results?
The results of the study are depicted in the figures below:
Figure 1: 8RM (in kg) performance in the Bench Press exercise
Figure 2: 8RM (in kg) performance in the Lat Pulldown exercise
Figure 3: 8RM (in kg) performance in the Leg Extension exercise
Figure 4: 8RM (in kg) performance in the Leg Curl exercise
In both the Bench Press and Leg Curl exercises only the No Stretching group increased their strength significantly. In the Lat Pulldown exercise all groups increased their strength, but the No Stretching group achieved much better results. In the Leg Extension Exercise, both the Pre Stretching and the No Stretching group were able to increase 8RM strength, but the No Stretching group increased more than the Pre Stretching group.
What did the researchers conclude?
The researchers concluded that static stretching before or during a strength workout diminishes strength increases and is therefore not recommended.
What does this mean for me?
-Static stretching during or before strength training reduces training progression.
-When flexibility is important as well perform static stretching after the strength training workout or on different days.
-To better prepare the muscles for an exercise, short dynamic stretching is recommended.
See also:
-The pro’s and cons of different stretching methods
Reference: