Too little recovery between sessions can suppress immune function

Circuit training is considered key for developing cardiovascular fitness and strength, but overdo it and you could be asking for trouble.

A study published in the journal Frontiers in Physiology looked at whether circuit training on two consecutive days affected the immune function of a group of fit volunteers who had been doing circuits for a minimum of six months beforehand.

For this trial, researchers recruited well-trained participants in CrossFit sessions, a commercial circuit class renowned for its high-intensity and short recovery time between exercise repetitions, and asked them to perform a circuit one day after the next. The sessions included Olympic lifting, power-lifting and gymnastic exercises using kettle bells, tyres and ring pull-ups.

Researchers assessed muscle power, levels of inflammatory cytokines and levels of metabolic markers, before, during and after the workouts.

According to Dr Ramires Tibana of the Catholic University of Brasilia, the lead author, the consecutive sessions provoked a strong metabolic response and reduced the levels of anti-inflammatory cytokines – proteins produced by white blood cells that act to dampen inflammation.

In other words, the intense effort suppressed normal immune function.

“A rest day is important for recovery for subsequent training sessions,” said Dr Tibana. “Other alternative recovery techniques are regenerative training (with low intensity and volume), massage and cryotherapy.”

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