In the ongoing chase for gains, variations from the basics of “lift heavy” and “progressive
overload” are sometimes given extra attention.
One of such variations is the case of partial reps.
The chief support argument for partial reps is maximizing the enigmatic mechanic called
time under tension.
The thing is, tension drops during the top and/or bottom ends of a given movement.
Think of the bottom or top end of a bicep curl or the bottom end of a side lateral raise.
Little to no tension.
By stopping shy of these ends with partial reps, one will ensure a more sustained tension.
Time under tension has been deemed by some as an important factor in muscle hypertrophy,
especially for inducing greater cell swelling, aka the PUMP.
But as far as EVIDENCE goes, partial reps aren’t all that convincing.
In terms of muscle hypertrophy, two different studies looked at the effects of partial reps
versus full reps in preacher curls and squats.
Results show, in convincing fashion, that full reps were better for muscle growth.
In fact, for the preacher curl, full rep subjects saw greater gains despite performing 36% less
total work volume throughout the 10-week program.
One might make the case that time under tension wasn’t properly maximized specifically in
the squat study since the shallow squat group went half way down but returned to a complete
standing position, mitigating tension duration.
However, the same cannot be said of the preacher curl.
The partial reps were sustained right within the center ranges, keeping tension strong
throughout the entire set.
This puts some doubt as to whether time under tension is of any relevance to actual muscle
growth adaptation.
But not to cast aside partial reps entirely, perhaps we were focusing on the wrong mechanism.
What might be of more relevance is a stretch-mediated response, theorized that, more hypertrophic
stimulation occurs when load is placed in angles where the muscle’s length is the
longest.
This is typically the starting point of the concentric or upward phase of any exercise.
A 2014 study do seem to show this in action.
They employed several exercises that involved knee extension, such as the knee extension
exercise, squats, and leg presses.
The major difference is the range each group trained in.
One group performed each given exercise within the range of 40 to 90 degree knee flexion,
classified as the long muscle length group.
The other, the short length group, employed a flexion range of 0 to 50 degrees.
After 8 weeks of this training, the long-length muscle group had significantly greater increases
in fascicle length (29 to 14%), muscle cross sectional area (53 to 18%), and greater levels
of IGF-1 (31 to 7), an anabolic hormone.
A study a few months later echoed the same sentiment with isometric knee extensions at
long and short muscle lengths.
Certainly, more research will still be needed to prescribe a more formative approach, but
stretch-mediated muscle growth does look promising.
Now looking at strength, undoubtedly training with partial reps will make you stronger at
… partial reps.
What would be more fascinating is if partial reps can translate to greater full rep output.
When it’s pitted directly against full reps, partial reps don’t stand much of a chance.
Returning back to the preacher curl and squat studies, full reps handedly beat out their
partial rep counterparts in improving 1 rep maxes for its respective full range movements.
One study in 2005 did find that partial reps in the bench press had, quote “positive
effects on strength across time within the parameters of the study.”
However, it’s important to note that this study was done with untrained women detailing
early phase adaptations.
Chances are that adaptations in this demographic will occur with any training protocol above
not having one at all.
But if it is true, then strength adaptations with partial reps might be a matter of exercise-specific
differences.
In any case, if there is a strength benefit to partial reps, it probably exists in the
ranges of longer muscle lengths.
The previous 2014 knee extension study found training in the long-length range elicited
26% greater strength gains compared to short-length’s 7%.
If there’s one thing to take away from this video, it’s this: training with full range
of motion, or the fullest you can safely achieve, is better than training with partial reps
for maximizing overall strength and muscle growth.
That being said, partial reps might still be a good occasional addition.
As mentioned, using partial reps during long muscle lengths have muscle and strength benefits.
Additionally, partial reps do allow you to work with a heavier load, much heavier than
your 1 rep max.
Some might be able to make the case that these extra heavy partial reps can ultimately translate
to greater full rep strength adaptations.
At least… in theory.
Let me know your thoughts on partial reps versus full reps in the comments below.
Are partial reps worth doing?
If you found this video valuable and helpful, please consider supporting PictureFit on Patreon.
Your support will help keep this channel going strong with more science-supported fitness
videos to come.
As always, thank you for watching and get your PROTEIN!