REF-1584 · Ahokas et al., 2023 · Biology of Sport · Paper · PubMed · Free full text

After one heavy strength-and-plyometric session, 20 min in a mild infrared sauna (43 ± 5 °C measured) instead of sitting at room temperature left 16 male basketball players with a smaller drop in countermovement jump 14 h later (−1.1% vs −5.0%), less soreness and better perceived recovery, while sprint, isometric strength, night-time heart rate, heart rate variability and sleep did not differ significantly; heart rate was higher and HRV lower during the sauna itself

Main caveat: Fewer analysed than randomised (14 for the jump, 11 for HRV); the authors call the HRV sample low.
moderate evidenceMeasured on trained to highly trained athletesRead in full

Ahokas and colleagues tested a single infrared sauna as a recovery tool after resistance training. Sixteen male basketball players did the same 60-min session of heavy lifts and jumps twice, a week apart, and afterwards sat either 20 min in an infrared cabin or 20 min at room temperature, in random order.

The next morning, 14 h after exercise, jump height had fallen less from that day's baseline after the sauna, soreness was lower and players rated their recovery higher. Sprint time and isometric leg-press force recovered without a significant difference between conditions.

During the sauna heart rate rose and HRV fell, but night-time heart rate and HRV, sleep duration and sleep quality did not differ. Muscle-damage markers did not differ either. The authors conclude that a single session improved recovery of explosive performance and soreness without harming autonomic recovery or sleep.

Participants

n = 16 men, 18.9 ± 2.3 y, 189 ± 8 cm, 83.4 ± 11.1 kg, 13.3 ± 5.7% body fat; two teams of one club (second tier n = 7, third tier n = 9); those under 18 had guardian consent.

Protocol

Session (60 min, familiar to the players): back squat 3 × 3 at 90-95% 1RM plus jumps; Nordic hamstring curl 3 × 5 plus standing long jumps; leg press 3 × 3 at 90-95% 1RM plus box jumps; order, loads and warm-up repeated in the second trial. Mean session RPE 8.1 ± 0.9 vs 8.3 ± 0.8 (p = 0.248).
Recovery: 20 min in an infrared cabin (set to 50 °C; measured 43 ± 5 °C, humidity 21 ± 1%) or 20 min sitting at room temperature.
Standardisation: 0.5 L water during exercise and 0.5 L during recovery; a recovery drink (8 g carbohydrate, 28 g protein) before recovery; food diary copied in the second trial; NSAIDs and other recovery methods not allowed.
Measures: jump, 20-m sprint and isometric leg press before and 14 h after (jump also 3 min after the session); fasted morning blood (cortisol, testosterone, SHBG, growth hormone, myoglobin, CK); HRV by chest ECG patch during recovery and over 4 h of each night; sleep diary; soreness on a 0-12 cm visual scale.
Funding and interests: Harvia Oyj (a sauna maker) and several foundations; the authors declare no conflict of interest.

Key Results

OutcomeSaunaPassivep
Jump change, before → 14 h−1.1 (4.5)%−5.0 (3.8)%0.009 (ES 0.76)
Jump height at 14 h (cm)40.9 (4.8)39.8 (5.7)0.129 between conditions
20-m sprint change+2.5 (1.4)% slower+2.7 (1.2)% slower0.631
Isometric leg press change0.0 (10.0)%−2.2 (6.7)%0.545
Heart rate during recovery (bpm)85 (6)72 (5)< 0.001
RMSSD during recovery (ms)26.7 (8.9)53.4 (15.0)< 0.001
Night after: RMSSD (ms) / heart rate (bpm)77.2 (37.4) / 53 (5)76.6 (36.4) / 52 (5)no significant time or condition effect
Soreness at 14 h (0-12 cm)2.9 (2.0)5.2 (3.0)0.005
Perceived recovery at 14 h (1-5)3.2 ± 0.72.6 ± 0.80.007
Morning cortisol at 14 h (nmol/L)423 (58)390 (57)0.005 (change from baseline did not differ, p = 0.306)
The jump drop straight after the session did not differ significantly (−6.0 ± 4.6% vs −7.9 ± 3.7%, p = 0.158).
Soreness change from baseline to 14 h: 0.9 (2.3) vs 2.1 (1.8), p = 0.032; baseline soreness was 2.0 (1.7) before the sauna trial and 3.1 (2.3) before the passive trial.
CK and myoglobin did not differ (change p = 0.640 and 0.446); testosterone and growth hormone showed no differences; sleep duration and quality did not differ (p = 0.377 and 0.632).
Analysed: jump 14, sprint 13, leg press 12 (absences, soft-tissue pain, and one outlier above mean + 2 SD removed); HRV 11 for nights and 11 during recovery.

Practical Application

Sauna after the gym and next-day recovery: in 16 young male basketball players, 20 min in a mild infrared sauna after a heavy strength-and-jump session left a smaller jump loss the next morning, less soreness and better felt recovery than sitting at room temperature, and night-time heart rate, HRV and sleep did not differ. One session, a mild cabin and no placebo, so read it as no sign of harm to overnight recovery plus a small, unblinded benefit, not proof of faster recovery.
Jump height at 14 h did not differ significantly between conditions (40.9 vs 39.8 cm, p = 0.129); the difference was in the change from each trial's pre-exercise baseline. Sprint and isometric strength recovered without a significant difference.
The authors note that participants could not be blinded and may have expected the sauna to help, which can colour soreness and perceived recovery.
Heart rate rises and HRV falls while sitting in the heat (85 vs 72 bpm here); the night readings did not differ. Inference, not tested here: an HRV reading taken right after a sauna reflects the heat and should not be compared with an athlete's usual post-session readings.
In their discussion the authors cite other studies in which a traditional sauna lowered strength for 24 h and a sauna after swimming impaired swimming the next morning; those are not tested here, and a Finnish sauna is a bigger heat load than this cabin.
Practice, not from this paper: the base's recovery guide lists sauna or hot water after training as "not as recovery" (SYNTH-70); this trial is a small positive signal for a mild infrared cabin after lifting, not a reason to change that line on its own.

Limitations

Fewer analysed than randomised (14 for the jump, 11 for HRV); the authors call the HRV sample low.
No placebo or blinding; self-reported soreness and recovery are open to expectation; baseline soreness differed between trials.
One session; trials ran during the season, and CK and myoglobin were already raised at the start of each trial.
Mild infrared heat only; men only; young team-sport players.
Funded in part by a sauna maker, with no conflict declared.
How this entry was checked and changed
Why this level

randomised crossover with 16 randomised (15 or more); jump, sprint and strength are performance outcomes and soreness and perceived recovery are self-reports. Fewer were analysed (jump 14, sprint 13, leg press 12, night HRV 11) and blinding was not possible; the "no harm to overnight recovery" part rests on HRV, a marker, in 11 players, and on its own would be B