Muscular balance is much, much more than scoring well in front of the judges at a bodybuilding contest.
If an imbalance exists between agonist-antagonist muscle groups, joint instability, muscular dysfunction, muscle weakness and increased risk of musculoskeletal pain and injury may result.
The goal of all professionally managed fitness programs is not only to balance the health and fitness needs of the client regarding all 10 Components of Fitness (strength, speed, power, anaerobic & aerobic endurance, agility, balance, coordination, flexibility and body composition), but to make sure the body is developed in complete balance.
This will require more fitness assessments than their 1-RM Bench Press and more exercise prescription than 1 or 2 exercises per body part. Muscle balance ratios differ between muscle groups and are affected by the force-velocity of different muscle groups at specific joints.
Ideally, you would use isokinetic dynamometers; however, in all practicality, most personal fitness trainers use 1-RM testing for each individual muscle group. The current standard for muscle balance ratios recommended for the agonist-antagonist muscle groups are:
Muscle Balance Ratio
|1. Ankle Inverters & Everters||1:1|
|2. Ankle Plantar Flexors & Dorsiflexors||3:1|
|3. Elbow Flexors & Extensors||1:1|
|4. Hip Flexors & Extensors||1:1|
|5. Knee Flexors & Extensors*||2:3|
|6. Shoulder Internal & External Rotators||3:2|
|7. Shoulder Flexors & Extensors||2:3|
|8. Trunk Flexors & Extensors||1:1|
*Note: In previous FitBits, it was reported that if the hamstring group does not have at least 75% of the strength of the quadriceps’ strength, the resulting imbalance could cause tearing of the hamstrings.
Female athletes experience at least 10 times the amount of hamstring pulls due to this imbalance. Muscle imbalance between other muscle groups is equally important. The imbalance between the strength of contralateral muscle groups (left vs. right sides) should not be allowed to become greater than about 10-15%.
You can easily see from asymmetrical sports such as tennis, the results of contralateral development causing injury. Strength training can be used to correct this type of imbalance.
Muscle imbalance between upper and lower body muscle groups can also become problematic. The strength-to-body mass (BM) ratio of the upper body should be at least 40-60% of the lower body relative strength.
One standard is to compare the bench press 1-RM/BM to the 1-RM/BM of the Leg Press. To prevent muscular dysfunction, the bench press should be 40-60% of the leg press.
If you discover any muscular dysfunction caused by muscular imbalance, then your exercise prescription will require 2 or 3 sets/exercises on the weak side/group for every one performed on the strong side until balance is obtained.
Dr. Jim Bell,