Can Lifting Weights Make You Flexible?

Why has flexibility and stretching become such a complicated issue? Recent research has explored whether a strength (resistance) training program is sufficient by itself to increase joint flexibility.

To stretch or not to stretch? Should I stretch before and/or after training? Is static stretching better than dynamic stretching? Does resistance training increase or decrease flexibility?

Why has such an innocuous event such as muscle stretching become such a complicated issue? Recent research has examined this assumed mundane activity to determine if a strength (resistance) training program was sufficient by itself to increase joint flexibility.

In a study at the University of North Dakota, researchers attempted to determine how full-range resistance training (RT) by itself affected flexibility and strength as compared to only static stretching (SS) of the same muscle-joint complexes in untrained adults.

Here is what they did:

25 volunteers were randomized to either an RT or SS group. 12 volunteers comprised an inactive group and assumed the control group (CON). Pretesting was performed to address hamstring extension, hip flexion and extension, shoulder extension flexibility, and peak torque of quadriceps and the hamstring. The volunteers completed a five-week SS or RT program with the goal of either stretching or strength training the same muscle–joint complexes with similar movements and ranges of motion. Post-tests of flexibility and strength were then conducted.


  • No difference occurred in hamstring flexibility, hip flexion, and hip extension improvement between RT and SS, but both were superior to CON values.
  • There were no differences between groups on shoulder extension flexibility.
  • The RT group was superior to the CON in knee extension peak torque, but there were no differences between groups on knee flexion peak torque.

The results of this preliminary study suggest that carefully manufactured full-range RT programs can increase flexibility as well as conventional SS programs used in training programs.

Considering the potential practical significance of these results to strength and conditioning programs, it is recommended further studies using true experimental designs, larger sample sizes, and extended training should be conducted with the goal of confirming or disproving these results.

Based on this study, it is prudent to use a full range of motion when performing strength training exercises if you want to improve joint flexibility. Until further evidence is confirmed, to enhance joint flexibility without taking valuable time to perform too much static stretching, make sure you perform your strength training exercises through a full (and safe!) range of motion. You will then become both more flexible and stronger through a greater range of motion, thus able to exert more force.