Does the evidence really support full ROM?

Take-aways

1. Full ROM provides good adaptations all-around, but you can likely optimize adaptations by adopting a more thought-out ROM..

2. For performance outcomes, adopt the ROM that you are trying to get better in - the ROM involved in your sport/task of choice.

3. For muscle growth, lengthened partials have reliably produced more growth than full ROM (in 4 out of 5 studies to date). At the very least, the ~25 studies on isometric training at different muscle lengths, partial ROM at different muscle lengths and the aforementioned lengthened partials vs full ROM data suggest you want/need to emphasise longer-muscle lengths in your training if you want to maximise muscle growth.

   1. Try lengthened partials, control the eccentric preferentially at the stretched position, pause in the lengthened position, be explosive out of the lengthened position and/or use machines/exercises that load the lengthened position more heavily.

The de facto standard, when it comes to range of motion, has always been a full range of motion. Even when the first resistance training machines were made, manufacturer instructions always emphasised going through a full range of motion for both safety and effectiveness. This idea persists to this day, with partial range of motion training frequently being featured on “gym-fail” pages.

However, at its inception, like many other things in resistance training tradition, there was little scientific evidence behind this idea. Over the past 20 years or so, that has changed substantially, and we now have around 20-30 studies comparing different ranges of motion and training at different muscle lengths and the impact this has on muscle size.

In our meta-analysis, we sought to review the literature on ROM and its influence on both muscle strength and muscle size. Additionally, since this was the topic of my PhD, I have also stayed up-to-date with the literature since the publication of this review.

In this article, I will try to keep it brief while providing take-aways from the literature.

Our meta-analysis included a total of 27 studies comparing a partial to a full ROM. When outcomes weren’t grouped (e.g. muscle growth vs strength) and partial ROM was simply compared to full ROM, here’s what the results looked like.

When a very rudimentary analysis was performed, full ROM outperformed partial ROM by a statistically trivial effect size (0.12; 95%CI: -0.02, 0.26).

Importantly, though, this type of analysis leaves something to be desired. After all, when it comes to performance outcomes like strength, for example, the outcome may matter. If we’re trying to improve our full ROM squat, that is a different goal, involving a different ROM, vs trying to improve our quarter squat. So, we analyzed the data based on the match between ROM performed in training and the ROM of the outcome. If the ROM of the outcome was a full ROM, for example, we categorized this as “FULL-bias”, and vice versa. If the ROM didn’t squarely fall into either the full or partial protocol (e.g. an isometric), we categorized it as “No Bias”. Essentially, this would allow us to determine whether performance adaptations are range of motion-specific or not.

Indeed, the results suggested that specificity played a large role. When the outcome was neither partial nor full ROM, both approaches were similarly effective at improving performance. However, when the outcome involved a specific ROM, training in that ROM specifically induced the greatest improvements.

This is informative, but the same question applies to hypertrophy. Around 5 studies on isometric training and around 9 studies comparing partials at different muscle lengths suggested that the muscle length at which training is performed can influence muscle hypertrophy (i.e. when training is performed at longer-muscle lengths, it consistently produces more hypertrophy). So, what happens when we sub-categorize partial range of motion training based on the muscle length it is performed at? For the purposes of this analysis, a partial ROM was considered “short” if it was performed, on average, at shorter-muscle lengths than the full ROM - not necessarily at the shortest-muscle lengths possible.

In line with the evidence on isometric training and partial ROM performed at different muscle lengths, the three studies included in this analysis that involved partial reps at longer-muscle lengths suggested a statistically small benefit to longer-muscle length - or lengthened - partials over full ROM for muscle growth (-0.28; 95%CI: -0.81,0.16). Importantly, two studies (one published, one only presented at a conference) have surfaced, both finding significant benefits to lengthened partials over full ROM, too.

Why?

First, let’s make one thing clear: full ROM is not magical. While it’s been the traditional choice for a long time, the evidence doesn’t support its unconditional use.

For performance, it appears you want to train in the specific ROM you’re trying to get better at. This may have to do with a shift in the length-tension relationship - in other words, your muscles/nervous system adapting to make you stronger specifically at the joint angles that you expose yourself to during that task.

For hypertrophy, we’re not too sure yet. It seems that the benefit is predominantly mediated by spending more time at longer-muscle lengths/that stretched position (after all, the same findings are evident in the isometric data, for instance). This could be due to greater passive tension. Your muscle-tendon-unit is something like a rubber band. As you stretch it past its resting length, it will build up (passive) tension to return to its resting length. Since tension initiates the hypertrophy response, spending more time at longer-muscle lengths could simply initiate that hypertrophy response to a greater extent. But, we’re just not very sure yet - and anyone claiming otherwise is making some large leaps of faith.