Lifters sometimes use a method called antagonist paired sets, which works opposing muscle groups at the same time. I have personally used this method with great success, but in the scientific literature it has been met with some mixed results.
The mixed results are a product of the huge number of potential variables at play with this protocol. A research team tried to nail down some of these variables in a recent Journal of Strength and Conditioning Research study.
Whenever you perform an exercise, both the agonists (the muscles moving the weight) and the antagonists (the muscles that oppose the agonists) are activated. The stretch reflex, responsible for the knee jerk reaction at the doctor’s office, is likely a primary reason for the activation of the antagonists. This reaction supports stability of the joints by preventing hyperextension or hyperflexion. Without it, you would constantly be injuring yourself.
However, despite its protective benefits, the stretch reflex yields smaller net forces during exercise. This is the basis of the antagonist paired sets method. If an antagonist muscle group is fatigued prior to performing an exercise, they will be less able to create a strong stretch reflex. This method should be used only as an advanced technique in experienced lifters, since you are actively reducing joint stability when you use it.
In the Journal study, the researchers chose to focus on rest intervals as the key variable. The participants were tested for their ten-rep maxes in both knee extension and knee flexion. Each person tried knee extension all by itself and also after a bout of knee flexion. They used four rest intervals between the knee flexion and extension:
- Thirty seconds
- One minute
- Three minutes
- Five minutes
Not only did the researchers measure performance, but this was also the first study of its kind to record EMG activity, which measures the degree of activation of the muscles. It’s possible that even if performance dropped, the muscles might be activated to a greater extent.
The researchers found that antagonist pairing improved performance when the antagonist exercise was performed immediately before, thirty seconds before, and one minute before the agonist set, but not longer. They also noted some increased EMG activity with up to thirty seconds as well. To give you an idea of the significance of this, when the knee flexion was done immediately prior to the knee extension, the ten-rep max could be performed for thirteen reps, which was a thirty percent improvement in repetitions.
So antagonist pairing does work, at least on single-set efforts. Since the much-written-about post-activation potentiation (PAP) has also been shown effective, but after a longer rest period, I’d love to see a study that pairs PAP and antagonist pairing to see if further benefits result. Imagine if every set could be fifty percent better. Science is a wonderful thing.
References:
1. Marianna de Freitas Maia, et. al., “Effects of Different Rest Intervals Between Antagonist Paired Sets on Repetition Perfomance and Muscle Activation,” Journal of Strength and Conditioning Research, DOI: 10.1519/JSC.0000000000000451
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