Key result
Short and long CrossFit sessions elevate 24-hour CK, with immediate spikes following long workouts.
Why the study?
CrossFit sessions vary by factors such as duration, which can elicit different responses, but the acute effects of short- versus long-duration sessions on tissue damage, autonomic responses, and fatigue required comparison.
Does a short-duration CrossFit session compared to a long-duration session elicit different acute effects on tissue damage, autonomic response, and fatigue in experienced practitioners?
RCT (n=13)
Counterbalanced
Does a short-duration CrossFit session compared to a long-duration session elicit different acute effects on tissue damage, autonomic response, and fatigue in experienced practitioners?
Both short- and long-duration CrossFit sessions induce significant acute tissue damage and autonomic stress, highlighting the need to consider workout intensity and duration for recovery.
May inform duration-specific recovery planning after CrossFit; leaves open confirmation in randomized trials.
Background: The main characteristics of CrossFit® are that it is constantly varied and of high-intensity. The planning of CrossFit® training sessions can be differentiated by modality, frequency, rest intervals, variation, and duration, which can elicit different responses. Purpose: The aim of the present study was to compare the acute effects of a short-duration ( Fran ) and long-duration ( Cindy ) session of CrossFit® on tissue damage (creatine kinase-CK), autonomic responses, and fatigue in experienced CrossFit® practitioners. Methods: Thirteen men (31.2 ± 3.2 years) with 5.72 ± 2 years of experience participated in a crossover study with a counterbalanced design, where they completed both the short-duration and long-duration CrossFit® sessions. Blood samples were collected to check tissue damage via CK, autonomic responses were verified through heart rate variability (HRV), and the fatigue by countermovement jump (CMJ) at the following moments: pre-workout, immediately after (IA), 24- and 48-hour after the training session. Results: A statistically significant increase in CK was observed for Fran at 24 hours versus pre-workout ( p = .029), while for Cindy there was a statistically significant increase in CK IA ( p = .002) and 24 hours versus at pre-workout ( p = .002). HRV showed lower values ( p < .05) IA for the time domain in Fran and for the frequency domain in both training sessions. HRV returned to pre-workout values at 24 hours. CMJ did not show significant differences between moments and training sessions. The present study showed that CK significantly increased from baseline just after the long-duration session and was increased 24 hours after both. HRV significantly decreased IA, except in the frequency domain for the shortest training session ( Fran ). CMJ did not change through 48 hours after training, regardless of the training session. Conclusions: Overall, these findings emphasize the importance of considering both the intensity and duration of CrossFit® workouts when assessing their impact on physiological responses and potential risks.
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Toledo et al. (2025) conducted an RCT in Experienced CrossFit practitioners (n=13). Short-duration CrossFit session (Fran) vs. Long-duration CrossFit session (Cindy) was evaluated on Tissue damage (creatine kinase-CK), autonomic responses (HRV), and fatigue (CMJ). Both short-duration and long-duration CrossFit sessions significantly increased creatine kinase at 24 hours, with the long-duration session also increasing it immediately post-workout.
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