In terms of arm isolation exercises specifically meant to target the biceps, the hammer curl and bicep curl play a definitive role respectively - being among the most commonly performed isolation movements in practically any training program.
However, despite their similar mechanics and muscle group activation, certain key characteristics of each exercise make them distinct from one another, requiring exercisers to understand these differences so as to maximize their effectiveness.
Fortunately, the hammer curl or the bicep curl do not necessarily need to be picked over the other, as both are equally effective in the right capacity, and may even work far better when used concurrently rather than alone.
The hammer curl is a bilateral or unilateral isolation exercise performed in order to induce muscular hypertrophy and strength development in the majority of the skeletal muscle groups attaching along the humerus, radius and ulna.
It is generally performed with the use of a dumbbell, kettlebell, or triceps barbell with a moderate level of resistance and higher volumes of repetition that train both type 1 and type 2 skeletal muscle fibers in an equal manner.
The hammer curl differs most significantly in the fact that the exerciser utilizes a neutral grip throughout the repetition, quite distinct from the supinated grip found in the bicep curl and thus also resulting in a somewhat altered muscular activation pattern and resistance distribution among the biceps brachii and the forearm muscles.
Much like the fittingly named bicep curl, the hammer curl targets the two headed muscle group that is the biceps brachii, increasing its size and definition while providing slow but clinically significant strength developments in the muscle.
The bicep curl is a unilateral or bilateral isolation exercise also performed for the purposes of increasing the size and strength of the biceps brachii, with other muscle groups related to the mechanics of the biceps being delegated to stabilizer muscle group duty alone.
Much like the hammer curl, the bicep curl is also performed with the use of such free weight exercise implements like kettlebells or dumbbells - but may also be performed with EZ curl barbells or straight olympic barbells, unlike the aforementioned hammer curl exercise.
The bicep curl makes use of a supinated hand grip during its traditional variation, positioning the exerciser’s palms in a manner that faces their torso and thus recruiting the biceps brachii in a far more significant manner than other biceps isolation movements - though with several drawbacks that may make the biceps curl unsuitable in certain situations.
Unlike its neutral grip counterpart, the bicep curl’s form and mechanics are somewhat more complex - and may require an intermediate level of resistance exercise experience in order to completely master and perform in a completely effective manner.
Both the hammer curl and the bicep curl are considered to be highly effective biceps brachii isolation movements that may be performed at any stage of an individual’s exercise career, though the capacity to which these exercises train the biceps alone can actually vary between the two.
This is mostly due to the difference in the angle of resistance and the mechanics of biceps contraction in relation to wrist positioning - with the hammer curl’s neutral grip recruiting muscles that are otherwise almost entirely ignored during the biceps curl.
As such, for exercisers wishing to induce training stimulus in these additional muscle groups as well, they may be better off focusing on the hammer curl as opposed to the bicep curl instead.
Though the hammer curl is first and foremost considered a biceps isolation movement, it primarily works the outer or long head of the biceps muscle group, thereby improving upon the thickness of the upper arm - all of which is primarily because of its neutral grip positioning shifting the resistance in such a manner.
Alongside this activation is its unique capacity to train the brachioradialis along the top of the forearms, alongside the brachialis that sits next to the biceps brachii on the outer portion of the upper arm.
Development in both of these muscle groups will result in a marked improvement in the thickness and definition of the arms, as well as an improvement in the pulling strength of the exerciser such as would be utilized in the barbell row or pull up.
The very definition of a biceps isolation movement, the bicep curl primarily utilizes the short or inner head of the two headed biceps brachii muscle group in order to move the weight most efficiently - though this may be altered somewhat through changing the angle at which the forearms are in relation to the elbow.
Unlike the hammer curl, the bicep curl does not significantly activate the muscle groups within the forearms or elsewhere along the upper arm, thereby only utilizing such muscles in a static capacity.
This will generally equate to the exerciser being unable to move as much weight as they would with the hammer curl - though the level of intensity in regards to biceps brachii activation should be much the same.
The hammer curl is doubtless an effective exercise for developing mass and strength in the biceps brachii muscle group - though not as effective as the biceps curl itself.
This is due to the fact that the biceps curl is, quite fittingly, an exercise made entirely to target the biceps brachii, with the entirety of its mechanics being geared towards utilizing the biceps in their fullest range of contraction.
As such, even with a lower level of resistance than would be possible with the hammer curl, the biceps curl is far more effective at inducing sufficient training stimulus in the biceps brachii.
In the case of the exerciser seeking out an effective forearms builder, the hammer curl would be a more suitable choice than the biceps curl as its neutral grip requires that the brachioradialis acts as a primary mover muscle throughout the entirety of the hammer curl’s repetition.
This, over time, can equate to not only thicker and stronger forearms, but also an eventual strengthening of all tissues in the wrist and elbows, improving not only the skeletal muscle tissue but also the connective tissues and bones therein.
In addition to the hammer curl’s capacity to strengthen the forearms, the neutral grip positioning of the hammer curl will also greatly reduce any incidence of injury involving the wrists, as well as reduce the amount of shear force placed on the connective tissues that make up the wrists.
The bicep curl and the hammer curl are both low impact free weight exercises that place little to no risk of injury on the exerciser’s joint and muscular tissues.
However, in the case of the bicep curl, the usage of improper form or excessive amounts of weight can raise the risk of such conditions as wrist or elbow tendonitis and shoulder impingements from occurring - especially if the exerciser does not perform proper preparatory work such as a mobility routine and adequate warm-ups.
Another risk presented by the bicep curl but not by the hammer curl is that of a biceps brachii tear; wherein the exerciser places excessive stress on the biceps brachii muscle itself and thereby tears its attachment or insertion points at either end of the upper arm - requiring a great deal of rehabilitation and surgery to recover from.
Luckily, this particular injury is rather uncommon and only occurs in exercisers lifting weight in excess of what they would be capable of with proper form.
In conclusion, in terms of safety, it is the hammer curl that far exceeds the bicep curl - though that is not to say that the hammer curl is entirely safe on its own as well.
Potential biceps brachii overtraining out of the equation - the combination of the biceps curl and the hammer curl can in fact be more beneficial than simply performing one exercise or the other.
This is because of the fact that the brachialis and brachioradialis act as agonists to the antagonist triceps brachii muscle group during exercises that contract them, something that allows them to work perfectly in tandem with the biceps brachii.
So long as the exerciser is careful with the fatigue they are inducing in all relevant muscle groups, combining the hammer curl and the bicep curl should lead to an excellent training stimulus that will result in faster and more effective muscle development.
Both the hammer curl and the bicep curl are used as auxiliary isolation exercises for the purposes of training the biceps brachii - usually alongside compound pull type exercises that recruit the biceps brachii and brachioradialis to a small but significant degree.
In terms of repetition volume, most sets of the hammer curl and the bicep curl are performed with the same amount of repetitions; usually anywhere between 8 to 20 repetitions, with higher repetitions potentially hinting at the need for higher levels of resistance.
In periodization utilizing training programs, they are often added at the end of hypertrophy blocks or conditioning blocks that require high levels of volume in isolation exercises.
In terms of relative exertion and the level at which all muscle groups concerned are recruited in, it is the biceps curl that may be considered more intense than the hammer curl - though this will still depend on the particular amount of weight and volume of repetitions used during the set.
The intensity of the bicep curl primarily comes from its longer range of motion, as well as the fact that the biceps brachii alone are tasked with the responsibility of acting as a primary mover muscle group, thereby raising the relative perceived exertion the exerciser will undergo.
When going over all the aforementioned information and inferring from it, one may come to the conclusion that the hammer curl is superior over the bicep curl in certain situations, as well as the opposite being true depending on the circumstances and needs of the exerciser.
However, this is primarily in niche situations; as in the case of general training, neither the hammer curl nor the bicep curl are superior over the other - rather, they are meant to work in tandem with one another so as to achieve proper arm muscle group development.
As such, it is our advice that the exerciser not only incorporate one of the two exercises into their training routine, but to also consider the benefits of the other exercise as well - with the usage of both, either in the same workout or in an alternating fashion resulting in a more well-rounded and effective training program.
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