Research Review: Resistance Training Matches Stretching for Flexibility While Adding Strength

BLUF (Bottom Line Up Front)

This 8-week randomized controlled trial compared resistance training and static stretching for improving flexibility and strength in healthy young adults. Both methods improved flexibility equally. However, only resistance training improved maximal isometric strength at both mid- and end-range joint angles. Static stretching had no effect on strength. When stretch intensity and training time were matched, resistance training was as effective for flexibility and superior for strength.

---

Purpose of the Study

To compare the effects of resistance training (RT) and static stretching (SS) on:

1. Flexibility (sit-and-reach)

2. Maximal isometric strength (straight-legged deadlift at 50% and 95% hip range of motion)

---

Subjects

• 18 healthy, physically active adults (13 women, 5 men), aged 19–30

• Randomized into 3 groups of 6 participants each:

  • Resistance Training (RT)

  • Static Stretching (SS)

  • Control (CON)

• All were novice lifters, free from injury, and compliant across 8 weeks

---

Methods

• Duration: 8 weeks, 3 sessions/week

• Stretch intensity and time matched across RT and SS (8/10 discomfort, 32 seconds per set)

• RT Exercises:

  • Straight-legged barbell deadlift

  • Modified Jefferson curl (kettlebell), tempo: 3 sec eccentric, 1 sec concentric

• SS Exercise:

  • Seated forward static stretch (32 seconds per set)

• Testing:

  • Sit-and-reach for flexibility

  • Isometric straight-legged deadlift (ISLDL) at 50% and 95% ROM using force plates

---

Key Findings

1. Flexibility (Sit-and-Reach)

• RT group: Improved by an average of 6.6 cm (estimated range: 4.0 to 9.2 cm)

• SS group: Improved by an average of 6.1 cm (estimated range: 4.7 to 7.5 cm)

• No meaningful difference between RT and SS

• Control group: showed minimal improvement (0.8 cm)

• Takeaway: Resistance training improved flexibility just as much as static stretching.
  (Ranges estimated using mean ± standard deviation)

2. Strength – End Range (95% ROM)

• RT group: Increased by an average of 145 newtons (estimated range: 118 to 172 newtons)

• SS group: Decreased slightly by an average of 16 newtons (estimated range: −73 to +41 newtons)

• Control group: Improved by an average of 49 newtons (estimated range: 5 to 93 newtons)

• Takeaway: Only resistance training improved strength at full range of motion.
  (Ranges estimated using mean ± standard deviation)

3. Strength – Mid Range (50% ROM)

• RT group: Increased by an average of 139 newtons (estimated range: 86 to 192 newtons)

• SS group: Improved slightly (17 newtons), but not significantly

• Control group: Improved slightly (23 newtons), but not significantly

• Takeaway: Resistance training improved strength at mid range. Stretching did not.
  (Ranges estimated using mean ± standard deviation)

---

Conclusion

When training time and stretch intensity are matched, full-range resistance training improves flexibility as effectively as static stretching—while producing significantly greater strength gains. Static stretching did not improve strength. Resistance training offers a more efficient and effective approach for building both mobility and strength in healthy, active individuals.

---

Bibliography

Rosenfeldt, M., Stien, N., Behm, D.G., Saeterbakken, A.H., & Andersen, V. (2024). Comparison of resistance training vs static stretching on flexibility and maximal strength in healthy physically active adults: a randomized controlled trial.BMC Sports Science, Medicine and Rehabilitation, 16:142. https://doi.org/10.1186/s13102-024-00934-1