Bodybuilders typically split their weight training workouts to allow enough time for muscle rebuilding through the recovery process. While a Crossfit WOD (workout of the day) is always at least a little bit different from yesterday's workout or tomorrow's, daily high-intensity effort might make recovery more difficult. A study published in the journal Frontiers in Physiology reports on the effect of WODs on 2 consecutive days.
Researchers had CrossFitters with 6 months of training experience take on a pair of WODs involving Olympic lifts, power lifts and gymnastic exercises on back to back days. They were told to finish each session as quickly as possible without compromising form.
The effort produced a strong metabolic response that reduced levels of anti-inflammatory cytokines. There was no adverse impact on muscle power, but less experienced practitioners might be suppressing their immune system in the process.