Hot or cold after exercise: what a 2026 study found about ice baths

Hot or cold after exercise does not have one universal winner: a 2026 trial in 40 active adults found that hot-water immersion, warm-air exposure and quiet rest all returned leg strength to about 88 to 89 percent of baseline within 72 hours after damaging eccentric work, while cold-water immersion reached about 82 percent on the same test. Ice baths are still widely used, and this study does not ban them. It does show that feeling less sore and getting strength back are not always the same outcome, and that heat-based recovery changed some blood markers faster than cold in this protocol.

TL;DR

Finding (72 hours after eccentric leg exercise)	Hot water (42°C, 30 min)	Warm air (30°C, 30 min)	Quiet rest (18°C room)	Cold water (9°C, 15 min)
Strength vs baseline (approx.)	88–89%	88–89%	88–89%	~82%
Creatine kinase-MM (muscle damage marker)	Back near baseline by 48 h	Normal by 72 h	Normal by 72 h	Still elevated at 72 h
Heat shock protein 72 (HSP72)	Increased more vs cold	Increased more vs cold	Lower than heat groups	Lower rise
Muscle soreness (all groups)	Still above baseline at 72 h	Still above baseline at 72 h	Still above baseline at 72 h	May feel less sore early; not fully resolved

• Population: 40 healthy, physically active adults (31 men and nine women in the author’s public summary), 10 per recovery arm, published in the Journal of Thermal Biology in 2026.
• Exercise: single bout of eccentric knee extensions designed to cause temporary damage and DOMS.
• Takeaway for regular trainers: pick heat, cold or simple rest based on whether you care more about next-day comfort, strength bounce-back, or convenience—not because any one method clearly dominated every measure.

Why are ice baths so popular after hard training?

Cold-water immersion went from niche sports science to gym culture in a decade. Athletes post ice-bucket clips; amateur lifters copy them after leg day. The usual story is that cold reduces inflammation, eases delayed-onset soreness, and helps you train again sooner.

That story is plausible but incomplete. Inflammation after hard exercise is part of repair and adaptation, not only a problem to shut down. Reviews over the years have reported mixed results on performance, soreness and long-term strength gains when cold is used often. A 2026 randomized trial led by researchers at the University of East London adds a direct comparison: cold versus heat versus doing almost nothing, measured with strength tests and blood markers—not only a soreness scale the next morning.

What did the 2026 hot-and-cold recovery study test?

The peer-reviewed paper is titled “Comparative effects of thermal recovery strategies on strength, muscle soreness and molecular markers following exercise-induced muscle damage in healthy adults,” published in the Journal of Thermal Biology (DOI 10.1016/j.jtherbio.2026.104551).

Design in plain terms:

• Who: 40 healthy, physically active adults, randomized into four parallel groups with 10 people each.
• Hard session: One bout of eccentric knee extensions on a machine that loads the quadriceps while the muscle lengthens under tension—the same pattern as lowering a heavy squat or running downhill.
• Right after exercise: One of four recoveries, assigned at random:
  • Hot-water immersion (HWI): 30 minutes at 42°C.
  • Cold-water immersion (CWI): 15 minutes at 9°C (shorter duration is common in cold protocols to limit hypothermia risk).
  • Hot-air exposure (HAE): 30 minutes at 30°C and 30% relative humidity (sauna-like warmth, not peak sauna temperature).
  • Control (CON): 30 minutes at 18°C and 30% humidity—sitting in a comfortable room, i.e. passive rest.
• Follow-up: Maximal voluntary contraction (MVC) strength, soreness and pain scores, and blood tests for interleukin-6, heat shock protein 72 (HSP72), and creatine kinase muscle-specific isoenzyme (CK-MM) over 72 hours.

This is one study in young-to-middle-aged active adults after a single damaging protocol. It does not speak for marathon week, contact-sport bruising, or years of daily ice baths during a strength block.

What happened to strength after the workout?

Immediately after the eccentric bout, MVC fell by about 36 percent in every group—expected muscle fatigue and damage.

Over 72 hours, strength climbed back in all arms. By the end:

• Hot water, warm air, and passive rest groups reached roughly 88 to 89 percent of baseline MVC.
• The cold-water group reached roughly 82 percent of baseline MVC.

The authors report significant main effects of time and group on MVC, but no statistically significant time-by-group interaction and no statistically significant between-group difference at 72 hours on strength—meaning the overall recovery curves looked broadly similar even though the cold arm ended slightly lower on this snapshot.

For a recreational lifter or runner, the practical read is subtle: none of the fancy recoveries produced a dramatic superpower comeback in three days. Cold did not clearly win, and on this strength test it ended a step behind the others.

What did blood markers show about muscle damage and heat stress?

Strength is what you can produce on demand. Blood markers hint at what is happening inside the muscle.

Creatine kinase-MM (CK-MM): A common sign of muscle membrane stress. In this trial, CK-MM rose after exercise in all groups. It returned toward baseline by 48 hours in the hot-water group and by 72 hours in warm-air and control groups, but remained elevated in the cold-water group at 72 hours. That fits the idea that cold did not speed the biochemical “clean-up” phase in this protocol—at least not on this marker.

Heat shock protein 72 (HSP72): A cellular stress protein linked to protection and repair pathways. Heat-based recoveries produced a larger post-session rise in HSP72 than cold immersion did, with a statistically significant time-by-group interaction.

Interleukin-6 (IL-6): Rose acutely after exercise in all groups; patterns differed by recovery, with hot-water immersion showing the highest immediate post-intervention IL-6 before a faster decline in the authors’ analysis.

These biology details matter because they separate “I feel fine” from “my muscle can produce force again” and from “my blood still shows damage.” Wearables rarely touch that layer. If you use a readiness score from a band or ring, treat it as sleep and autonomic trend data, not as a readout of CK-MM. Our guide to Whoop vs Oura vs free trackers explains what those morning numbers actually combine.

Did ice baths at least reduce soreness?

Muscle soreness and pain scores rose by 24 hours in every group and were still elevated at 72 hours—none of the interventions fully erased soreness in three days.

Cold-water immersion is often praised because athletes feel better soon after a plunge. In public commentary on this trial, lead author Freya Bayne noted that cold can reduce perceived soreness even when strength and some markers lag—a reminder that comfort and function can diverge.

If your only goal is to walk stairs without wincing after a novel leg session, a brief, safe cold dip might still be worth trying for you individually. If your goal is to hit the same squat numbers two days later, this study suggests heat or even quiet rest matched hot water as well as or better than cold on the strength test used.

How does heat compare to a sauna or a hot shower?

The trial’s warm-air arm was 30°C air for 30 minutes, milder than many commercial sauna settings. Hot water was 42°C for 30 minutes—hot tub territory, not lukewarm bath water.

Do not copy those numbers blindly at home. Hydrate, limit alcohol, exit if you feel dizzy or nauseous, and avoid extreme heat if you are pregnant or have cardiovascular disease unless a clinician clears it. A normal shower or a shorter, cooler soak is fine for most people who are not researching a lab protocol.

What should you do this week if you train hard?

Use this study as a decision filter, not a mandate.

If you are in a strength or hypertrophy block where you want muscles to adapt between sessions, stacking ice baths after every leg day may not be necessary—and could feel worse on strength tests like those in this paper. Many lifters already schedule rest days and easy walks instead of extreme recoveries.

If you compete on back-to-back days (tournament sport, Hyrox-style weekends), a short cold dip might help you feel ready even when biology is still catching up. Know that feeling is not proof.

If you hate cold, passive rest, sleep, food, and gentle movement remain evidence-backed basics. Protein across the day from beans, tofu, eggs, dairy or lean meat, enough fluids, and seven to nine hours of sleep still do more for most people than any tub temperature.

If you love heat, a warm bath or sauna-style session after hard work aligns with the HSP72 and CK-MM patterns seen here—but match intensity to your health status and the weather.

Log a simple experiment for two weeks: note temperature, duration, session type, soreness at 24 hours, and whether the next planned workout happened at planned load. Trends beat one viral clip.

Goal	Reasonable first try	What to watch
Less next-day soreness	10–15 min cool (not icy) shower or brief cold immersion if medically safe	Sharp joint pain, not just muscle ache—stop
Strength back for next leg day	Prioritize sleep, food, 48+ h before repeating heavy eccentrics	Weights that feel stuck for two weeks—deload
Low hassle	Walk, mobility, normal meals	Mood and sleep slipping—see stress and load
Data-curious	Same recovery for two weeks, compare to baseline weeks	One device’s green score does not prove recovery

When should you see a professional instead of tweaking recovery hacks?

See a clinician or sports medicine provider if you have:

• Chest pain, fainting, or palpitations during or after exercise or hot-cold exposure.
• Joint swelling, locking, or sharp pain—not typical muscle soreness.
• Numbness, blue or white fingers that do not rewarm, or whole-body shivering you cannot stop after cold.
• Confusion, severe headache, or vomiting during or after heat exposure.
• Soreness that worsens for more than a week without a clear reason, or pain after a pop or twist in the knee or ankle.

Cold and heat can stress the heart and circulation. They are not substitutes for diagnosing a stress fracture, tendon tear, or rhabdomyolysis.

This is general training guidance, not medical advice.

Related

• Rest days: how many you need and what to do on them
• Whoop vs Oura vs a free tracker: what recovery scores actually measure
• Is your training going up or down? Reading workout trends
• Stress, burnout and when to deload
• Sleep calculator · Heart rate zones · Sleep tracking features

Sources

• Bayne F et al. Comparative effects of thermal recovery strategies on strength, muscle soreness and molecular markers following exercise-induced muscle damage in healthy adults. Journal of Thermal Biology 2026. https://doi.org/10.1016/j.jtherbio.2026.104551
• Bayne F. Hot or cold? Our research explores what works best after exercise. The Conversation 2026 (author plain-language summary of the same trial). https://theconversation.com/hot-or-cold-our-research-explores-what-works-best-after-exercise-295514