Do Longer Muscle Lengths Enhance Muscle Growth? New Research Explores the Evidence
Whether you use the new 'lengthened partial' lifting method or stick to a full range of motion, new evidence suggests both methods result in equal hypertrophy. However, when it comes to growing muscle in specific regions, researchers have examined the effects of training at different muscle lengths.
The Study
The systematic review and meta-analysis preprint aims to examine how muscle length during resistance training influences regional muscle hypertrophy. The study mentions that previous research has found that muscle growth can occur in a 'non-uniform manner,' with growth varying along the length or across different compartments of a muscle group — referred to as 'regional hypertrophy.' By manipulating training variables such as exercise selection and training at specific muscle lengths, these regional or 'site-specific' changes in the muscle may be elicited.
The Methods
The researchers analysed 12 studies. The inclusion criteria for these studies were that the participants were young and healthy and had participated in resistance training for a minimum of four weeks. The studies compared training at different joint angles or through different muscle lengths. The studies also had to assess regional hypertrophy through at least two measurement points along the length of the muscle.
The Results
The results indicate that longer muscle lengths, when compared to shorter muscle lengths, do not elicit a significant difference in regional hypertrophy. This includes the proximal (closest to the body), mid-belly (middle of the muscle), and distal (furthest from the body) muscle regions. The study found only trivial to small effects regarding the impact of muscle length on muscle growth.
The Conclusion
The researchers concluded that they found 'trivial effects of mean muscle length on regional muscle hypertrophy estimated with relatively high precision.' They continued to add that while training at longer muscle lengths could potentially cause more growth at distal muscle sites than at proximal sites, the effect wasn’t strong enough to be practically meaningful.
They note that 'this suggests it is more probable that effects are practically equivalent when contrasting 'shorter' and 'longer' mean muscle lengths as opposed to being superior with longer mean muscle lengths.' In other words, the effect of training at longer muscle lengths does not appear to be significantly better than training at shorter lengths. Instead, the muscle growth results between the two lengths are very similar.
What Does This Mean for Us?
The research concludes that there are no significant differences in training at varied muscle lengths on muscle growth at different sites of the muscle. This means that we don't need to prioritise training at specific muscle lengths to achieve muscle growth at certain points.
Since these are some of the finer details when it comes to training for hypertrophy, we needn't worry about adjusting our range of motion with these variables when our goal is to grow muscle in a specific area.
According to previous research, eccentric-only strength training and concentric-only strength training can affect regional hypertrophy, with eccentric-only strength training causing more muscle growth in the distal part of the muscle, while concentric-only strength training leads to greater growth in the middle part.
Another study used in this review found that using a full range of motion may enhance muscle activation across the entire muscle length, potentially promoting balanced muscle growth. For now, it's best to prioritise a full range of motion during your lifts for optimal muscle growth across the entire length of the muscle.
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