Bicep Curls: Are they necessary for biceps strength?
One way to categorize exercises is into single-joint and multi-joint exercises. As their names imply, for some exercises, the action only occurs in one joint whereas in others, the action occurs across multiple joints. For example:
Bench press - action occurs in the shoulder and elbow joints
Tricep extensions - action mainly occurs in the elbow joint
Both workout the triceps but the joints involved differ slightly.
Another example: The bicep curl is a single-joint exercise (only elbow joint involved). The lat pull down is a multi-joint exercise (shoulder and elbow joints involved). Both workout the biceps muscle group.
Some have argued that single-joint exercises (like the bicep curl) must be included in a resistance training program to optimize muscular size and strength. The reason is because single-joint exercises usually "zone in" on working a specific muscle group compared to multi-joint exercises which often involve several muscle groups. In multi-joint exercises, one muscle might tire out more quickly giving the other involved muscles less of a workout. Or the main muscle involved (often called the prime-mover) may be doing most of the work resulting in lower activation of assisting muscles.
Gentil, P and colleagues reviewed the current literature to ascertain what the science says about whether single joint exercises are necessary to optimize muscular size and strength. Here are their findings and conclusions:
- Most studies, mainly of the legs, arms and chest suggest that there is little difference in activation and strength between single joint and multi-joint exercises.
- Even when a multi-joint approach is compared with a single-joint + multi-joint program, there is little difference. Adding single-joint exercises did not seem to add any additional benefit in strength.
- Studies do suggest that single-joint exercises may be necessary for increasing lumbar extensor strength
- These findings are consistent whether for shorter or longer term programs
- Similar results for trained or untrained individuals
For example, one study comparing lat-pull downs vs bicep curls found that there was actually greater muscle thickness in the biceps with the multi-joint lat-pull down workouts. Another study looked at lat-pulldowns vs a program consisting of both lat pull downs and bicep curls. No significant differences were found.
A separate investigation compared multi exercises like: incline bench presses, flat bench press, decline bench, weighted push ups, shoulder presses, v bar lat pull-downs, seated rows, etc, to a program that included the very same exercises with the addition of single joint exercises. The results? Both groups increased flexed arm circumference, muscle circumference and even 1 repetition maximum.
The paper authors conclude that performing single-joint exercises adds little benefit to a program except in the case when the goal is to increase lower back extensor strength. Their answer to the question: "Are single-joint exercises like bicep curls necessary?" would be in the negative. However, the purpose of sharing this paper is not to get people to take out single-joint exercises from their routines. It is important to note that the studies don't suggest single-joint exercises are detrimental either. Single-joint exercises add variety to a program which is important as well. My personal recommendation is to use papers like this to be informed on what current science is suggesting but some personal experimenting would not be a bad idea to figure out what actually works best for you.
Please refer to the reference below to read the full text of the article.
Gentil, P et al. A Review of the Acute Effects and Long-term Adaptations of Single-and Multi-joint Exercises during resistance training. Sports Med (2017) 47:843 - 855