It's not for want of repeating it regularly in our articles: resistance training offers a wide range of benefits for health, sports performance and, of course, body aesthetics. Gains in strength and muscle mass are, in fact, the goals of most people. Muscle hypertrophy depends on numerous training variables. While the total volume (sets x reps x load) to which a muscle is subjected is one of the most important variables for muscle mass gains, there are many others to consider. Among these, the choice of exercises is particularly important. Different exercises associated with the recruitment of a muscle can target particular regions of that muscle. What's more, some of these exercises may be more effective than others for optimal muscle recruitment. The process of selecting exercises when designing a training program is therefore paramount, as they will significantly influence hypertrophic adaptations.
While a thorough understanding of anatomy and biomechanics is essential for formulating hypotheses on exercise efficacy, it unfortunately doesn't always provide definitive answers, particularly when it comes to muscle hypertrophy. This is mainly due to the lack of anatomical information on living AND moving muscles. Digital muscle simulation models, although increasingly accurate, also fail to predict the hypertrophic potential of long-term exercise. The same applies to the limitations of tools such as electromyography (EMG). EMG, used to assess muscle activation during exercise, gives valuable indications, but cannot account for the complexity of muscle growth. It can indicate which muscles are engaged during exercise, but does not necessarily correlate directly with hypertrophy. This limitation becomes more pronounced when comparing exercise variants, where subtle differences in movement can lead to significantly different results in muscle development.
Figure 1. The triceps brachii.
It should also be noted that many exercise variants are not studied, which makes their use hazardous, as it's not possible to guess whether a variant will deliver better results, unless you take the time to test it and, perhaps, waste your time... This is the case with the position of the forearms in high pulley extensions, and its impact on triceps brachii recruitment. The triceps brachii is an arm muscle made up of 3 regions: the long portion, which is bi-articular, and the vastus medialis and vastus lateralis, which are mono-articular. These 3 chiefs all insert on the ulna, at the level of the olecranon, and thus act as the main extensors of the elbow. Most elbow extension exercises on the high pulley are performed with a pronated handle. However, some users also use a supinated handle. Given that the pronated/supinated forearm movement mainly involves pivoting the radius, and that the ulna does not change position, will this have an impact on the development of the triceps brachii and its chiefs?
In an attempt to answer this question, Brazilian researchers compared the effects of unilateral high-pulley extension with the forearm in supinated and pronated positions on recruitment of the vastus lateralis, the long portion of the triceps and two forearm muscles, the flexor carpi radialis and extensor carpi radialis.
To do this, they recruited 22 people (11 women and 11 men) aged between 18 and 35, with or without resistance training experience (13 people had trained more than 6 months). Each person performed the Triceps Push-Down exercise (vertical extension on the high pulley) unilaterally, according to 4 conditions: pronation with handle, supination with handle, pronation with strap attached to the forearm and supination with strap attached to the forearm. In each condition, participants performed a series of maximum repetitions with the same absolute load corresponding to 80% of 1RM in the supinated position with handle.
In the starting position (beginning of the concentric phase), the elbow was bent to 90°. The movement ended when the elbow was fully extended (0°). For each condition, the researchers analyzed the activity of the 4 muscles via EMG.
The main results of this study show that, with the same absolute load, recruitment of the vastus lateralis and the long portion of the triceps brachii is greater in the case of forearm supination with handle. Pronation with handle results in higher EMG activity for the flexor carpi radialis, compared with other exercise conditions. Supination with handle resulted in higher EMG activity for the extensor carpi radialis muscle. Finally, participants performed the fewest repetitions in supination with handle, and the most repetitions in pronation with strap.
One possible explanation for this result is a reduction in the external lever arm in pronation. In this position, the head of the radius rotates against the lateral side of the ulna at the proximal radio-ulnar joint, causing the body of the radius to cross the ulna, and consequently shortening the external lever arm slightly. This would explain why we are stronger with pronated forearms in this exercise. And why, in this study, EMG activity in the triceps is lower in this variant. By the same token, this would explain why in the strapped conditions, triceps EMG activity is lower: the external load is located more proximal to the elbow, which reduces the lever arm of external resistance. This would explain the lack of difference between pronation and supination when a strap is used.
The EMG activity of the long portion and vastus lateralis of the triceps between pronated and supinated handles can also be attributed to the involvement of the flexor carpi radialis and extensor carpi radialis muscles. In the handle condition, in pronation, the carpal flexors would be recruited to prevent wrist extension. Conversely, in supination, the carpal extensors would be recruited to prevent wrist flexion. But as the carpal flexors have a greater volume and strength than the carpal extensors, it is likely that the carpal flexors exert a greater influence on elbow extension, thus explaining the reduced demand on the triceps brachii during pronation handle.
When straps are used and attached to the forearm, there is no flexion or extension torque at the wrist, and consequently no recruitment of the flexor carpi radialis or extensor carpi radialis muscles, which would explain the similar recruitment of the triceps regardless of forearm position.
In terms of the maximum number of repetitions performed, the conditions with the strap enabled a higher number of repetitions, as the lever arm of the external resistance in relation to the elbow is smaller. Conversely, with a handle, the lever arm increases, and with it the external force moment, requiring greater involvement of the triceps brachii.
For the same absolute load, using a handle in supination is more difficult and will therefore require greater recruitment of the triceps brachii. It remains to be seen whether, for the same relative load, the triceps brachii would be better solicited in supination or pronation; and in the long term, which would benefit its muscular development more. It may also be worth considering the use of forearm straps to avoid any "parasitic" muscle recruitment linked to the moment of force created at wrist level.
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