Sore From the Gym, Flat on the Bike: Managing DOMS Around Key Sessions

Most triathletes who start lifting meet the same problem. The first leg session goes well, the next day feels fine, and then the following day's bike intervals feel impossible. Stairs are awkward and the run feels flat. It's easy to conclude that strength training and endurance training don't mix.

They do mix, and TriForward's "The Minimum Effective Dose" and "Two Sessions a Week" cover why lifting is worth the time. But the soreness is real, it has a measurable effect on endurance performance, and it follows a predictable pattern. This article covers what delayed-onset muscle soreness (DOMS) is, how much it costs your next session, why it fades after the first few weeks, and how to schedule lifting so your key sessions don't pay for it.

What DOMS is

DOMS is the aching, tender stiffness that appears several hours after unfamiliar or strenuous exercise, usually peaks around one to two days later, and fades over the following days. It's most associated with eccentric work, where a muscle lengthens under load: lowering into a squat, lowering a weight in a Romanian deadlift, landing from a jump or running downhill.

DOMS is a sign of exercise-induced muscle damage, but the soreness and the damage don't line up exactly. The research below uses several markers alongside soreness:

• Loss of strength or jump height, usually the most useful marker of how much function has been lost.
• Reduced range of motion and swelling.
• Blood markers such as creatine kinase (CK), which leaks from damaged muscle.

For a triathlete the practical question isn't how sore you are, it's how much the next bike or run session suffers.

How much does it cost the next session?

A trial in trained cyclists

The most relevant study is a 2024 trial by Devantier-Thomas and colleagues in the European Journal of Applied Physiology. It recruited 10 trained male cyclists, aged 38 ± 13 years, riding 150 to 300 km a week, who hadn't done lower-body resistance training for six months.

• The session: 3 sets of 6 repetitions at 95% of six-repetition maximum on Smith-machine back squat, single-leg press, leg extension and leg curl. In other words, heavy but not unusual gym work.
• The design: they did the same session twice, at least two weeks apart, and were tested the day before and 24 and 48 hours after each one.
• The tests: soreness, jumps, submaximal cycling efficiency and a 10 km simulated time trial.

After the first session:

• Soreness rose at 24 and 48 hours.
• Countermovement jump fell from 28.3 to 25.5 cm at 24 hours, about 10%.
• Average power in kilometres 1 to 3 of the time trial fell from 281 W to 269 W at 24 hours, about 4.5%, and was still about 3% lower at 48 hours.
• Effort felt harder at submaximal intensities, with rating of perceived exertion up about 8% at 24 and 48 hours.
• Overall time-trial duration didn't change significantly.

After the second session, soreness was significantly lower at both 24 and 48 hours. That's the repeated-bout effect, covered below.

Note that the percentage changes here are calculated from the reported averages, not tested individually. The main point is the direction: an unfamiliar heavy leg session made the start of a hard effort weaker and made submaximal riding feel harder for a day or two, even if the total time held up.

Plyometrics and a 15-minute time trial

An older study by Burt and Twist in the Journal of Strength and Conditioning Research (2011) used a deliberately muscle-damaging plyometric session. It involved 17 participants (15 men, 2 women), randomised to a plyometric group or a control group.

• 48 hours after the jumps, the plyometric group had significant soreness and lost strength.
• In submaximal cycling at ventilatory threshold, oxygen uptake, ventilation and perceived effort were higher.
• In a 15-minute time trial, mean power output and distance covered were lower than before, while perceived effort was the same.

That last point matters. The riders didn't feel they were trying less hard. They simply produced less power at the same effort.

What a review concluded

A 2017 review by Doma, Deakin and Bentley in Sports Medicine pulled together studies of endurance performance after single resistance sessions. They concluded that residual fatigue from one resistance session can impair a following endurance session for several hours to several days if recovery is inadequate. They proposed four mechanisms:

• Altered neural recruitment.
• Reduced movement efficiency, with changed technique and higher energy cost.
• Muscle soreness.
• Lower muscle glycogen.

They also argued that if endurance session quality is compromised again and again, long-term endurance development may suffer, though that link isn't fully established. Their advice was to adjust the order of sessions, the recovery between them and the intensity of the lifting to limit carry-over fatigue.

The repeated-bout effect

Here's the part that changes how you plan. After one bout of muscle-damaging exercise, muscles adapt so that a similar bout causes much less damage, soreness and loss of strength. This is called the repeated-bout effect.

A 2017 review by Hyldahl, Chen and Nosaka in Exercise and Sport Sciences Reviews described it as a well-established adaptation whose mechanisms are still not fully understood. They proposed that several processes work together:

• Neural changes in how the muscle is recruited.
• Changes in the mechanical properties of the muscle and tendon.
• Remodelling of the connective tissue around the muscle fibres.
• Biochemical and inflammatory signalling.

For a triathlete, the mechanism matters less than the pattern: the first session of a new exercise is the expensive one.

How long does the protection last?

A 2026 study by Theodorou and colleagues in the Scandinavian Journal of Medicine and Science in Sports tested this directly. 48 young men did two identical bouts of maximal eccentric knee-extensor exercise. Four separate groups did the second bout 3, 6, 9 or 12 weeks after the first.

• At 3 and 6 weeks, the repeated-bout effect was clear for most outcomes.
• At 9 weeks, it was still detectable for some markers.
• At 12 weeks, there were no significant differences between the first and second bouts. Strength, range of motion, soreness and muscle ultrasound measures showed no meaningful protection.

These were young men doing an extreme, isolated eccentric protocol, not triathletes doing squats. Inference: if you stop lifting for two or three months, such as over a long race season or an injury break, expect the first sessions back to hurt again.

Light sessions protect too

You don't need a damaging session to get the protection. In a 2013 study in the European Journal of Applied Physiology, Chen and colleagues studied 26 healthy older men with a mean age of 66.

• The experimental group did a light session of eccentric knee extensions, lowering a weight equal to 10% of their maximal strength, a week before a maximal eccentric session.
• The control group did only the maximal session.

The light session itself caused no measurable damage or soreness. But after the maximal session, the experimental group lost less strength and range of motion, recovered faster and had smaller changes in the other markers. Inference: a deliberately light first session of a new exercise appears to buy protection for the heavier sessions that follow, at almost no cost. TriForward's "The Masters Training Week" uses the same study for older athletes.

Who gets sore, and how much?

The trials above are almost all in men, and most are small. Two points are worth knowing:

• Eccentric and unfamiliar work causes the most soreness. Deep squats, Romanian deadlifts, lunges, step-downs and jump landings tend to cause more than cycling-like movements such as leg press.
• Individual responses vary widely. Some people barely notice a new session, others are sore for days. Your own history is a better guide than the averages.

Women are underrepresented, and the evidence on whether women experience less muscle damage than men is mixed, so this article doesn't assume a sex difference either way.

Does anything make DOMS go away faster?

Many triathletes reach for recovery tools. A 2018 meta-analysis by Dupuy and colleagues in Frontiers in Physiology compared post-exercise recovery techniques across 99 studies. Massage was the most effective technique for reducing DOMS and perceived fatigue, and massage and cold exposure were the most effective for inflammation markers.

Effects on soreness don't necessarily mean better performance, and TriForward's "Foam Rollers and Massage Guns" found that rolling has only small, short-lived effects. Inference: recovery tools may make you feel better, but avoiding a big unfamiliar dose in the first place is far more effective than treating the soreness afterwards.

Scheduling lifting around key sessions

The following suggestions combine the studies above. They're inference for triathletes, not a tested programme:

1. Start each new exercise light. For the first one or two sessions, use loads well below what you could manage and fewer sets. The Chen study suggests this buys protection for later sessions.
2. Increase load gradually. Big jumps in load or volume, or a new exercise, restart the cycle.
3. Leave 48 hours between an unfamiliar or heavy leg session and a key bike or run session in the first few weeks. The cyclist trial still showed lower early time-trial power at 48 hours.
4. Pair lifting with hard days, not before them. Many triathletes lift on the same day as a hard session, after it, so that the following day is easy. TriForward's "Lifting and Endurance in the Same Week" covers session order in more detail.
5. Keep lifting through the season. Even one familiar session a week may maintain protection. Gaps of 12 weeks appear to lose it completely.
6. Keep eccentric-heavy work away from race week. Familiar, lighter lifting is unlikely to cause problems. New exercises, extra sets or a heavy session you haven't done for weeks are the risks.

A triathlon scenario

The following example is illustrative, not drawn from a study. A 41-year-old triathlete training for a half-distance race in June decides to start lifting in November. On Monday she does three sets of eight heavy squats, Romanian deadlifts and walking lunges, all new to her. On Wednesday her threshold bike intervals are well below target and she abandons the session.

A better plan, based on the evidence above, might be:

• Week 1: one or two sets of each exercise with light loads, on the same day as an easy swim.
• Weeks 2 to 4: add load and sets gradually, keeping key bike and run sessions at least 48 hours after lifting.
• From week 4 or 5: once soreness is minimal, move lifting to the afternoon or evening of a hard day, so that the next day is already easy.
• Through the season: keep one or two familiar sessions a week, reducing volume in the fortnight before her race rather than stopping altogether.

Common mistakes

• Starting with a heavy session. The first exposure to an exercise causes the most soreness, so it shouldn't be the heaviest.
• Concluding that lifting doesn't suit you after the first fortnight. Soreness usually falls sharply once the repeated-bout effect kicks in.
• Stopping lifting for the whole race season, then restarting with a heavy session in the autumn.
• Adding a new exercise in race week because it looked useful on social media.
• Running hard downhill or doing new plyometrics before a key session. Both are eccentric loads, and the Burt and Twist study used jumps to cause damage.
• Relying on recovery tools rather than managing the dose.

How DOMS fits with training load

DOMS also has a monitoring use. If you track training load or heart rate variability, as described in TriForward's "Reading the Trend, Not the Number", unusual soreness is one more signal. Inference: soreness that keeps appearing after familiar sessions may mean the lifting load has increased too fast, or that overall training and recovery are out of balance, rather than a problem with lifting itself.

What we don't know

• Whether these effects apply to triathletes. No trial has tested strength-session soreness and the next swim, bike or run in triathletes.
• Women's responses. The cyclist trial included only men, and the repeated-bout duration study included only young men.
• The effect on running. Most of the performance data here comes from cycling, and running involves more eccentric loading, so soreness may matter more.
• Long-term effects. Whether repeatedly compromised sessions in the first weeks of lifting actually limit endurance gains over a season isn't clear.
• The minimum dose for maintaining protection through a race season.

References

• Devantier-Thomas B, Deakin GB, Crowther F, Schumann M, Doma K. The repeated bout effect of traditional resistance training on cycling efficiency and performance. European Journal of Applied Physiology, 2024;124(7):2005–2017. doi:10.1007/s00421-024-05422-5
• Burt DG, Twist C. The effects of exercise-induced muscle damage on cycling time-trial performance. Journal of Strength and Conditioning Research, 2011;25(8):2185–2192. doi:10.1519/JSC.0b013e3181e86148
• Doma K, Deakin GB, Bentley DJ. Implications of impaired endurance performance following single bouts of resistance training: an alternate concurrent training perspective. Sports Medicine, 2017;47(11):2187–2200. doi:10.1007/s40279-017-0758-3
• Hyldahl RD, Chen TC, Nosaka K. Mechanisms and mediators of the skeletal muscle repeated bout effect. Exercise and Sport Sciences Reviews, 2017;45(1):24–33. doi:10.1249/JES.0000000000000095
• Theodorou AA, Margaritelis NV, Karyofyllidou AV, Christodoulou F, Jamurtas AZ, Fatouros IG, et al. The duration of the repeated-bout effect after eccentric exercise. Scandinavian Journal of Medicine and Science in Sports, 2026;36(10):e70381. doi:10.1111/sms.70381
• Chen TC, Tseng WC, Huang GL, Chen HL, Tseng KW, Nosaka K. Low-intensity eccentric contractions attenuate muscle damage induced by subsequent maximal eccentric exercise of the knee extensors in the elderly. European Journal of Applied Physiology, 2013;113(4):1005–1015. doi:10.1007/s00421-012-2517-3
• Dupuy O, Douzi W, Theurot D, Bosquet L, Dugué B. An evidence-based approach for choosing post-exercise recovery techniques to reduce markers of muscle damage, soreness, fatigue, and inflammation: a systematic review with meta-analysis. Frontiers in Physiology, 2018;9:403. doi:10.3389/fphys.2018.00403