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7 min readrunning / endurance

Ice baths blunt strength and spare endurance: when to get in

I race 100 km and put around 5,000 km a year on my legs, so a cold tub after a hard session reads like free money. Llion Roberts' group ran the study that made me start checking the calendar before filling one. Twenty-one physically active men trained their legs twice a week for 12 weeks. After every session, one group sat 10 minutes in 10°C water and the other pedalled easy for 10 minutes. The cyclists finished with 17% larger type II fibres, 19% more isokinetic work and 26% more myonuclei per fibre. The cold group gained none of the three 1.

What the cold costs in a strength block.

A second group replicated the pattern with a different design. Sixteen men lifted three days a week for 7 weeks, then spent 15 minutes in either 10°C or 23°C water. Leg press 1RM rose the same amount in both groups, a pooled effect size of 1.53. Type II fibre cross-sectional area separated them: the cold group came out about 1,959 µm² behind, an effect size of -1.37 2. Strength held up while the fibres underneath it grew less.

Piñero's team pooled the eight studies available on immersion and muscle growth. Resistance training on its own produced hypertrophy effects around a standardised mean difference of 0.36 (95% credible interval 0.10 to 0.61). Resistance training followed by cold water landed at 0.14, with the interval crossing zero (-0.08 to 0.36) 3.

Elvis Malta's group asked the same question across both training types. Eight controlled trials, repeated immersion at 15°C or below against passive recovery, inside real training programmes. Strength outcomes, pooling 1RM, isometric strength, strength endurance and ballistic power, came out at a standardised mean difference of -0.60 (p < 0.0001). Endurance outcomes, pooling time trial mean power, maximal aerobic power and graded exercise test performance, came out at roughly 0.00 4.

Runners keep their adaptations.

James Broatch's team ran 6 weeks of sprint interval training with immersion after every session. A single session raised phosphorylated AMPK, p38 MAPK and p53 along with PGC-1α mRNA, and the cold water left all four responses alone. Over the 6 weeks, peak aerobic power, maximal oxygen uptake, maximal uncoupled respiration and 2 km time trial performance all improved, with no gap between the immersion group and the control group 5.

A 2026 trial repeated it on runners. Five weeks of high-intensity interval running, immersion after each session, and the measurements that matter to a distance athlete stayed level: satellite cell pool, intramuscular inflammatory markers, PGC-1α expression, VO2max and running performance 6.

The cost sits in the hypertrophy pathway. Endurance adaptation runs through mitochondrial signalling, and none of these trials found cold water interfering with it.

What the tub buys.

Jonathan Leeder's meta-analysis measured soreness at 24, 48, 72 and 96 hours. In the high-intensity exercise subgroup the effect was large: Hedges' g of 1.675 at 24 hours and 1.391 at 48 hours 7. After eccentric work, which is closer to what a long downhill does to a runner, the numbers were smaller.

The largest synthesis on performance comes from Moore's group: 52 studies comparing immersion with passive recovery after one hard bout. After high-intensity exercise, cold water came out ahead at 24 hours on muscular power, muscle soreness, creatine kinase and perceived recovery. After eccentric exercise, only muscular power at 24 hours survived. In their meta-regression, shorter immersions at lower temperatures worked better for creatine kinase and for endurance performance 8. Machado's earlier dose analysis converged on 11 to 15°C for 11 to 15 minutes 9.

The ritual carries part of the effect.

Broatch's group also tested belief against temperature. Thirty men sprinted 4 times for 30 seconds, then took 15 minutes in one of three conditions: 10.3°C water, 34.7°C water sold to them as a recovery treatment, or plain 34.7°C water. Leg strength and the ratings of readiness, pain and vigour came out worse in the plain condition. Cold water and the sham finished together 10.

Thirty men and one sprint session make thin ground for a general claim. The result still sets the bar for anything I assert about my own tub: part of what I feel afterwards comes from having done something deliberate.

The protocol.

  1. Fill the tub when the next hard effort is inside 48 hours. Race tomorrow morning, a stage race, day two of a camp: get in. A Tuesday long run with the next quality session on Friday: skip it and take the soreness.
  2. Use 11 to 15°C for 11 to 15 minutes, legs and hips submerged, once, within an hour of finishing 89. Colder and longer buys nothing the meta-regression could find.
  3. Keep the tub out of a strength block. During weeks when leg strength and muscle mass are the target, the 17% fibre gain and the 26% myonuclei gain are what you are training for 1. The trials above immersed within 15 minutes of the last set, so a bath 6 hours later sits outside the evidence. I treat that gap as unknown, not as a loophole.
  4. Ice without worry inside an endurance block. Six weeks of sprint intervals and five weeks of interval running produced the same VO2max, the same time trial and the same mitochondrial markers with cold water as without 56.
  5. Expect less from it after a long downhill than after a track session. Eccentric damage is where both syntheses found the weakest effects 78.
  6. Score the first session after each immersion out of 10, in the same notebook as the session itself. Twenty entries in, compare the average against your non-immersion weeks. Under 1 point of difference, the tub is buying comfort: keep it for race weeks and leave it alone the rest of the year.

Sources.

  1. Roberts, L. A., Raastad, T., Markworth, J. F., Figueiredo, V. C., Egner, I. M., Shield, A., Cameron-Smith, D., Coombes, J. S., & Peake, J. M. (2015). Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training. The Journal of Physiology, 593(18), 4285-4301. doi.org/10.1113/JP270570
  2. Fyfe, J. J., Broatch, J. R., Trewin, A., Hanson, E., Argus, C. K., Garnham, A., Halson, S. L., Polman, R., Bishop, D. J., & Petersen, A. (2019). Cold water immersion attenuates anabolic signaling and skeletal muscle fiber hypertrophy, but not strength gain, following whole-body resistance training. Journal of Applied Physiology, 127(5), 1403-1418. doi.org/10.1152/japplphysiol.00127.2019
  3. Piñero, A., Burke, R., Augustin, F., Mohan, A. E., DeJesus, K., Sapuppo, M., Weisenthal, M., Coleman, M., Androulakis-Korakakis, P., Grgic, J., Swinton, P. A., & Schoenfeld, B. J. (2024). Throwing cold water on muscle growth: A systematic review with meta-analysis of the effects of postexercise cold water immersion on resistance training-induced hypertrophy. European Journal of Sport Science, 24(2), 177-189. doi.org/10.1002/ejsc.12074
  4. Malta, E. S., Dutra, Y. M., Broatch, J. R., Bishop, D. J., & Zagatto, A. M. (2021). The Effects of Regular Cold-Water Immersion Use on Training-Induced Changes in Strength and Endurance Performance: A Systematic Review with Meta-Analysis. Sports Medicine, 51(1), 161-174. doi.org/10.1007/s40279-020-01362-0
  5. Broatch, J. R., Petersen, A., & Bishop, D. J. (2017). Cold-water immersion following sprint interval training does not alter endurance signaling pathways or training adaptations in human skeletal muscle. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 313, R372-R384. doi.org/10.1152/ajpregu.00434.2016
  6. Malta, E. S., Rosa Neto, J. C., Beck, W. R., Cornachione, A. S., de Poli, R. A. B., Sigoli, E., & Zagatto, A. M. (2026). Regular Cold-Water Immersion Following HIIT Does Not Affect Intramuscular Adaptation Markers, Inflammatory Profile or Endurance Performance. Scandinavian Journal of Medicine & Science in Sports. doi.org/10.1111/sms.70241
  7. Leeder, J., Gissane, C., van Someren, K., Gregson, W., & Howatson, G. (2012). Cold water immersion and recovery from strenuous exercise: a meta-analysis. British Journal of Sports Medicine, 46(4), 233-240. doi.org/10.1136/bjsports-2011-090061
  8. Moore, E., Fuller, J. T., Buckley, J. D., Saunders, S., Halson, S. L., Broatch, J. R., & Bellenger, C. R. (2022). Impact of Cold-Water Immersion Compared with Passive Recovery Following a Single Bout of Strenuous Exercise on Athletic Performance in Physically Active Participants: A Systematic Review with Meta-analysis and Meta-regression. Sports Medicine, 52(7), 1667-1688. doi.org/10.1007/s40279-022-01644-9
  9. Machado, A. F., Ferreira, P. H., Micheletti, J. K., de Almeida, A. C., Lemes, Í. R., Vanderlei, F. M., Netto Junior, J., & Pastre, C. M. (2016). Can Water Temperature and Immersion Time Influence the Effect of Cold Water Immersion on Muscle Soreness? A Systematic Review and Meta-Analysis. Sports Medicine, 46(4), 503-514. doi.org/10.1007/s40279-015-0431-7
  10. Broatch, J. R., Petersen, A., & Bishop, D. J. (2014). Postexercise cold water immersion benefits are not greater than the placebo effect. Medicine & Science in Sports & Exercise, 46(11), 2139-2147. doi.org/10.1249/MSS.0000000000000348

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