Réf :  Paulo Gentil, James Fisher, James Steele. (2017). A review of the acute effects and long-term adaptations of single-and multi-joint exercises during resistance training. Sports medicine, 47(5), 843-855.
​Translation and adaptation: Alexandre Paré - ATARAXIA

Introduction and context
Muscle training is well known to promote a significant increase in the volume and strength of skeletal muscle and therefore improve health-related parameters and reduce the risk of mortality.

Bodybuilding exercises can be categorized into two main categories: multiarticular (MA) and uniarticular (UA). The MA exercises recruit several muscles or groups of muscles in a synchronous manner, generally classified as prime mover or secondary muscle (synergists). For example, in the bench press, the pectoral major is often considered as the main muscle (the one exercising a dominant action), while the triceps and anterior deltoids are considered secondary muscles for this precise movement. muscles that assist the desired movement). 

This definition suggests that some muscles play a primordial role in the realization of the movement while the others, the synergistic muscles, have a more secondary role. This conceptualization of the roles of the muscles during precise movements made it possible to construct certain hypotheses according to which the synergistic muscle might not be sufficiently activated during the exercises MA due to the predominance of the main muscle.

Some authors have suggested that muscle hypertrophy would occur earlier with UA exercises compared to MA exercises because of the prolonged neurological adaptations that are required for AM exercises. As a result, many coaches and fitness enthusiasts believe that the addition of UA exercises to a bodybuilding program is necessary in order to optimize hypertrophy and strength.

In addition, respected organizations such as the American College of Sports Medicine (ACSM) make recommendations suggesting that bodybuilding sessions should include eight to ten exercises that are both multi-articular and uniarticular.

It should also be noted that lack of time is often cited as a reason for joining a training program. The time required to achieve these recommendations can be discouraging for many people. Therefore, it is important to find strategies that reduce the time spent in the gym without adversely affecting the results.

Strength training, which generates acute responses to muscle activation (EMG, micro-tear and fatigue) also leads to long-term adaptations (strength and hypertrophy). By comparing the MA and UA exercises on these two types of adaptation, one would think that the superiority of UA movements would be questioned. If the addition of DU exercises is not necessary, it would be possible to design shorter training programs with the same effectiveness.

Based on this state of mind, the purpose of this literature review is to analyze the scientific articles that have studied acute responses and long-term adaptations following exercise sessions containing AU or UM movements .

Methodology

Studies were considered eligible if they were genuine experimental studies comparing the effects of MU, UA or MU + UA. The authors did not consider literature reviews or article abstracts, or even whether they involved symptomatic populations or people with joint or musculoskeletal problems. Based on these factors, 23 studies have been integrated.

Results

For both upper and lower limbs, analysis of EMG suggests that there are no differences between the UA and MA exercises when comparing the main muscle. For example, the same levels of EMG were obtained on average by comparing the squat and the extension extension (made at the same% of the 1 RM) or the fly and the bench press, to name just a few.

One study only directly compared the effects of UA and MA exercises on muscle recovery. The results suggest that AU exercises created an increase in fatigue and muscle pain greater than the MA exercises.

Studies comparing hypertrophy and strength gain for upper limb muscles reported no difference between AU and MA exercises. Additionally, no additional effects were reported when DU exercises were included in an MU exercise program.

At the level of lumbar extensors, the studies examined tend to argue that this specific muscle group could benefit more from the AU exercises than from the AM exercises.

The analysis of the current literature suggests that the inclusion of AU exercises in a bodybuilding program is only justifiable for correcting imbalances between different muscle groups. This could be the case when preparing bodybuilders since they are evaluated at the level of symmetry and balance in their muscle development. Another possible use would be in a rehabilitation program when a muscle group presents an imbalance and represents a risk of increased injury or pain, such as rotator cuff, hamstring and gluteal muscles.

Conclusion

The results of this analysis suggest that the addition of UA exercises in a training program that already includes AM exercises would not yield any advantages when comparing short (EMG) and long term (strength and hypertrophy responses ), whether in trained persons or not. Fatigue, stress perception and pain seem to be more important for UA movements. However, as this does not appear to be accompanied by greater adaptation, the use of these exercises without distinction could be detrimental because they induce a higher malaise without producing superior results. The only currently experienced situation in which UA exercises could be recommended is for those wishing to strengthen the lumbar extensors. Based on these findings, those who do bodybuilding may not need to include DU exercises in their program to achieve equivalent results in terms of muscle activation and long-term adaptations such as exercise, hypertrophy and strength. AU exercises are probably only justifiable for strengthening the lumbar extensors and correcting muscle imbalances.