When you strength train, you probably do mostly full range-of-motion repetitions, although you might on occasion do sets like “twenty-ones” where you shift the focus to partial reps – or you might do partial squats for variety. Doing partial repetitions simply means you reduce the number of degrees of motion through which you move the joint you’re working. For example, with biceps curls, you bring the weight up to your chest and back down only halfway before lifting the weights back to the chest. Another situation where some trainees use partial reps is when the muscle is fatigued to the point that a full rep is too challenging. To eke a little more work out of the muscle, the trainee does a partial rep or two.
What Does Science Say about the Effectiveness of Partial Reps vs. Full Reps?
A study published in the Journal of Strength and Conditioning Research in 2017, showed that full range-of-motion repetitions, using elbow flexion exercises with free weights, led to greater muscle damage than partial reps. The participants in the study had greater markers of muscle damage 24, 48, and 72 hours after doing full reps as opposed to partial ones. In addition, the participants experienced greater soreness with elbow extension after doing partials. This was true despite the fact that the partial rep group was able to use a higher resistance because they weren’t moving the weight as far. That’s not to say that greater muscle damage will necessarily lead to greater muscle growth but there is a correlation.
Another study published in the Journal of Strength and Conditioning Research in 2005 compared upper body strength development using partial or full reps on bench press. The participants were divided into three groups. One group trained using three full range-of-motion bench press sets. A second group worked with three partial range-of-motion sets on the bench press. The third group, serving as a control, did both partial and full range-of-motion bench press sets. After 10 weeks of training twice weekly in this manner, all groups improved in strength but the group that did full range-of-motion sets made greater strength gains.
Other studies looking at full reps vs. partial reps also found full reps to be better than partial reps for building strength. In fact, a meta-analysis of six out of nine studies showed full reps to be superior to partial reps for strength gains, while three studies found no difference. So, if leg strength is your goal, focusing mostly on full squats makes sense based on the research that’s available.
Another area where full squats excel is for building power. You need leg strength to maximize your performance when you jump, swing a heavy kettlebell, or do jump squats. Studies show that full squats increase lower body power and maximize jumping performance to a greater degree than partial squats. Also, partial reps are effective for building strength within a specific range-of-motion. For example, if you do a half squat, you’ll develop strength within that specific range-of-motion but won’t develop as much overall strength for the full squat movement.
Full reps are better for hypertrophy gains as well. For example, several studies reveal that full squats are superior to partial reps for increasing muscle size in the thighs. This isn’t surprising since full squats increase time under tension, a stimulus for muscle growth. You can compensate for this by slowing the rep speed down when you do partial reps to keep the muscle under tension longer. One advantage of partial reps is that it’s harder to use momentum when you’re using a shortened range of motion, so you’re holding tension throughout the movement.
Should You Do Partial Reps?
Most of the evidence leans toward doing a predominance of full reps if the goal is to build strength. This is true for upper body training and lower body training. Not that partial reps don’t have a place in your workout. You can use them to correct points in a lift where weakness limits your performance. For example, if your “sticking point” on biceps curls is at the beginning of the movement, include partial reps where you work the biceps through the first 45 degrees of the movement using a heavier weight to correct the weak point of that lift. Using this approach helps you break through strength plateaus. When you do a partial rep using a heavier weight than you’re accustomed to, your nervous system calls more muscle fibers into play. When you return to full reps, your brain thinks you can handle more weight.
Another strategy is to incorporate both full reps and partial reps into your workout. You can do this for variety or use partial reps as a way to change the stimulus on your muscles when you reach a plateau. You can also use partial reps to get a little more out of a muscle you’re just worked. For example, do full reps to muscle fatigue and then try to do a few partial reps as a finisher. Pushing your muscles with partial reps when they’re already fatigued is a way to place additional stress on the muscles you’re working and trigger growth. Placing unaccustomed stress on your muscles is a good plateau buster.
Partial reps is an approach to fall back on if you have a minor injury and experience discomfort when you do an exercise through its full range-of-motion. If you don’t experience discomfort when you do partial reps, doing them might be a way to get a workout and maintain some level of strength until your injuries heal. You can start with partial reps and gradually increase the range-of-motion as you heal.
However, if you make the bulk of your workout partial reps, you’re cheating yourself out of gains. To maximize strength development and to build muscle size, you’ll get the most return working your joints through their full range-of-motion. The good news is you don’t have to choose. You can make both a part of your workout – just be sure that the bulk of your workout focuses on full repetitions.
Journal of Strength & Conditioning Research: August 2017 – Volume 31 – Issue 8 – p 2223–2230. doi: 10.1519/JSC.0000000000001562.
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