The debate around whether the stretched or contracted portion of a lift is more crucial for muscle growth has been raging for years. Many fitness enthusiasts and experts champion the importance of the stretch, citing its role in muscle hypertrophy. However, this emphasis on the stretch has been met with skepticism, particularly regarding its efficacy for experienced lifters. Many believe the benefits are primarily seen in beginners. This prompted a study to investigate the impact of range of motion on highly experienced trainees.
This research explored the effects of full range of motion (ROM) training versus lengthened partial ROM training on muscle growth in experienced lifters. Full ROM involves completing the entire range of motion of an exercise, while lengthened partials focus on the stretched portion of the movement. Prior research comparing shortened partials (focused on the contracted position) to lengthened partials consistently showed greater muscle growth with lengthened partials. Similar studies comparing lengthened partials to full ROM also favored lengthened partials in most cases.
One theory explaining the effectiveness of lengthened partials is sarcomere addition, where muscles grow in length rather than thickness. However, this is thought to occur primarily in beginners. To address this and the lack of research on experienced lifters, a study was conducted with participants averaging 4.9 years of lifting experience.
The study design involved each participant training one side of their body with full ROM and the other with lengthened partials for eight weeks. This within-subject unilateral design eliminated the risk of genetic variations skewing results, as each participant served as their own control. The training program consisted of four sets per exercise, utilizing both moderate and higher rep ranges. Participants were instructed to train to muscular failure on every set, ensuring training intensity.
Experienced lifter performing a bicep curl
The study used ultrasound to measure muscle growth on both sides of the body after the eight-week training period. The results revealed no statistically significant difference in muscle growth between the full ROM and lengthened partial groups. While the biceps data initially suggested an advantage for lengthened partials, statistical analysis confirmed no significant difference.
Researchers analyzing muscle growth data
These findings can be interpreted in two ways. Firstly, lengthened partials didn’t outperform full ROM, validating the effectiveness of full ROM training for those who prefer it. Secondly, achieving similar gains with half the range of motion (specifically the stretched half) suggests the potential efficiency of lengthened partials. This means experienced lifters might achieve equivalent muscle growth with less effort. Surprisingly, even eliminating the contracted portion of the lift entirely didn’t hinder gains, suggesting the squeeze may be less critical for hypertrophy than previously thought.
This study also tempers the enthusiasm surrounding the stretch. While the stretch remains an essential aspect of muscle growth, focusing on it exclusively may not significantly enhance gains in experienced lifters. The optimal range of motion likely varies depending on the specific muscle group and exercise. Previous studies have shown greater benefits from lengthened partials for calves and hamstrings, suggesting potential muscle-specific applications.
Participants training in the lab
For experienced trainees, both full ROM and lengthened partial training are effective approaches. The choice depends on individual preferences and specific exercises. While neglecting the stretch might limit gains, there’s flexibility in how it’s incorporated into training. Considering prior research on beginners, lengthened partials might still be optimal for certain muscles. This study contributes valuable insights into the ongoing debate about range of motion and muscle growth, offering practical applications for experienced lifters.
