PT on the Net Research

Muscle Balance


When testing muscle balance such as bicep to triceps, hamstring to quads, chest to back, etc. what is the goal for each of these relationships? I don't think they all need to be 100 percent equal, but at the same time, obviously they shouldn't be 4:1 either. Are there certain agonist/antagonist goals for each of these situations?


This is not a simple question. Determining muscular “balance” normally requires muscle testing that involves manual, somewhat subjective measures of how a muscle or muscle group functions throughout a range of motion. This should be carried out by a trained sports medicine professional, such as a physical therapist. For greater detail, look to Kendall’s Muscles: Testing and Function (Williams & Wilkins) or Kinakin’s Optimal Muscle Training (Human Kinetics).

You don’t mention a special target audience. My impression is you want to know what someone who regularly engages in resistance training needs to demonstrate in order to suggest his muscles are “balanced.” As a simple example, look at an arm curl and a triceps press. You want to determine a ratio of performance in two exercises, both single joint moves and both common exercises for a pair of opposing muscles.

Unfortunately, such a comparison (at least in the weightroom) does not take into consideration the effects of an individual’s muscle attachments, the speed of movement and limb length characteristics. But it’s a starting point.

One of the few ratios frequently documented is quadriceps to hamstrings. Utilizing the same testing apparatus and measuring/comparing simple, single joint movements like the knee (leg) extension and knee (leg) curl provides a ratio. For 50 years, it has been reported in scientific literature that one should aim to keep a ratio of 3:2 when training/measuring the quadriceps versus the hamstrings. This was originally stated as a safeguard against injury, particularly to the hamstrings. I imagine the ratios of those suffering from chronic hamstring injuries were compared to those without hamstring injuries, and this conclusion became gospel. More recent research suggests certain weaknesses in this suggested ratio, but again, it’s a decent general guideline.

I am unaware of any specific ratios for elbow flexion and extension.

Where such muscle balance testing becomes much more difficult is comparing, for example, “chest to back.” Testing the pectoral muscles can be carried out, as can testing of all the various “back” muscles. But drawing conclusions from such testing, or comparing bench press to bent over rowing, for example, is a stretch.

I’ve been tested on Cybex equipment that measured the differences in trunk flexion (mostly abdominals) and truck extension (spinal erectors, hamstrings), and this comparison is probably fairly well documented.

As you suggest, finding a 4:1 strength ratio between opposing muscles would be a cause for concern. Similarly, a 4:1 ratio between exercises that focus on opposing muscle groups would be a concern. But as you say, there’s no need to expect a 1:1 ratio, since again, we have to look at individual characteristics and biomechanics.

If you can identify more specifically certain exercises that you’d like to compare, then yes, I think the literature will provide some guidance. Certainly, there is a large body of knowledge relative to ratios of certain strength moves to certain explosive moves, for example. However, this is not measuring specific muscles or muscle groups but more total body performance.

As I mentioned in opening, your question is not an easy one to answer. I hope I’ve been able to shed some light on the subject.