Studies exploring
isometric training at different muscle lengths have identified differences in regional hypertrophy between training groups, but not always in muscle fascicle length (Noorkõiv et al. 2014).
Partial and full range of motion training are not as different as you might think from
isometric training at short and long muscle lengths.
On the other hand, regional hypertrophy (but not always muscle fascicle length) seems more important than changes in joint angle - specific neural drive for the joint angle - specific gains in strength after
isometric training at long muscle lengths (Alegre et al. 2014; Noorkõiv et al. 2014).
Traditionally, it has been assumed that neural factors were responsible for joint angle - specific gains in strength after
isometric training at all joint angles (Kitai & Sale, 1989; Noorkõiv et al. 2014).
The easiest way to understand how these factors drive the differences in adaptations between full range of motion training and partial range of motion training, is to look at
isometric training at either short or long muscle lengths.
And joint angle - specific strength gains are smaller than after
isometric training at short vs. long muscle lengths.
Similarly,
isometric training at short muscle lengths improves strength at that joint range of motion, and only improves strength very slightly (if at all) at longer muscle lengths.
Similarly,
isometric training at long muscle lengths is not as dissimilar as you might assume to full range of motion training with constant - load, free weight exercises.
Isometric training at long muscle lengths improves strength at that joint range of motion, and also (albeit slightly less) at shorter muscle lengths.
Not exact matches
Last November he stopped weight
training and began a set of
isometric exercises, pushing and pulling
at an immovable bar for a mere 15 minutes a day, including rest periods.
Isometric contractions were stimulated in muscles ex vivo using a Grass Technologies S48 stimulator
at a stimulation frequency of 120 Hz for EDL muscles and 80 Hz for soleus muscles, a stimulation current of 28 V, and duration of 500 ms. Muscle fatigue was analyzed using a repeated stimulation protocol lasting 6 minutes and consisting of repeated 40 - Hz tetanic
trains that occurred once every second and lasted 330 ms (62).
The
isometric training was performed with maximal speed - intent but without moving, while the isokinetic
training was performed with maximal speed - intent, and
at a relatively high angular velocity (300 degrees / s).
Interestingly, there was very clear evidence of velocity - specific transfer to the
trained speed, and this transfer tapered away to either side of the
trained speed, even though that zone included
isometric strength
at 0 degrees / s.
Similarly,
training using a partial range of motion (which is similar to using
isometrics at short muscle lengths) increases strength around the joint angle corresponding to the peak contraction.
You have to
train your central nervous system to be strong
at the end range of motion and a smart way of doing that is with
isometric contractions.
Isometric training is the easiest way to assess the effects of
training at either long or short muscle lengths (Alegre et al. 2014; Noorkõiv et al. 2015).
Thus, these studies suggest that the length of the muscle during strength
training may not be an important factor for altering muscle fascicle length,
at least when using
isometric contractions.
Dynamic strength
training through either a (1) full or a (2) partial range of motion (ROM) are similar to
isometric strength
training at either (1) long or (2) short muscle lengths, because the muscle is only really challenged
at the point of peak contraction, and this is
at the start of the concentric phase in most common exercises.