Does a swim tire your shoulders?
It depends on how hard you swim, and one small study draws the line clearly. Dekerle and Paterson worked out a critical speed for each of eight trained swimmers, average age about 20, from their 200, 400 and 800 m race times. In random order, the swimmers then swam six 5-minute blocks with 2.5 minutes of rest between them, once 5% faster than that speed and once 5% slower, and the strength of the muscles that turn the shoulder inwards was tested between blocks.
Below the line, nothing gave. Peak torque, blood lactate, effort, stroke length and stroke rate held steady across all six blocks. Above it, the shoulders tired. Lactate and effort climbed, the stroke shortened, and peak torque fell from 35.0 to 25.8 Nm on average, about a quarter. None of the swimmers could hold that pace much beyond 20 minutes.
Short sprints count too. The review covered in the next section cites a second study, of ten male international swimmers, in which four 50 m swims at maximum effort reduced arm strength, measured as elbow flexion force, and the activity of the biceps and triceps.
On this page, a hard set is repeats faster than a pace you could hold for a long swim: breathing hard at every wall and fading by the last one. An easy swim is one you could keep going at. The study's slower set was not easy, at 95% of critical speed, and it still left the shoulders intact, though the authors think the 2.5 minutes of rest after each 5-minute block may have helped. That is why we read an easy swim as no threat to the gym (our view).
Eight swimmers is a small sample, and only one shoulder movement was tested, so treat the result as a clear signal rather than a rule. The authors themselves say a causal link between the shorter stroke and the lost strength "should be considered very cautiously".
Swim before or after weights?
Within a day, the gap between the two decides how the second session goes. A 2022 review by Arsoniadis and colleagues gathered the studies of competitive swimmers and water polo players who lifted and swam on the same day. None of them tested lifting first against swimming first head to head, and the authors say the research does not allow a safe conclusion on the better order. Across separate studies, both orders seemed to improve performance over six to twelve weeks, and the authors name the recovery time between the sessions, and what each one contains, as the factors to watch.
The short-term studies show why the gap matters:
- Heavy lifting just before sprints hurt them. In nine male competitive water polo players aged about 22, bench press and leg press at 80% of one-rep max, 20 minutes before eight all-out 25 m sprints, slowed both the best and the average sprint. A lighter session at 50% did not slow the best one.
- Steady swimming coped better. In 12 well-trained male swimmers aged about 19, heavy lifting about 40 minutes before a steady 5 x 400 m set did not affect performance in that set, though blood lactate ran higher.
- Hours apart worked. When the two sessions were about seven hours apart on the same day, studies reported gains in maximum strength and repeated sprints.
- For long-term gains, minutes were enough. Across the training studies, 10 to 15 minutes between the sessions, in either order, was enough for performance to improve over weeks. The gap matters most for how the second session itself goes.
The samples are narrow: average ages from about 13 to 30, almost all of them male, and the authors note the lack of data on competitive women. For an adult who swims for fitness and lifts for strength, it is a guide, not a rule written for you. Read together with the shoulder study above, it points to one question: what did the swim spend? After an easy or technique swim, the gym session can follow. After a hard set, leg work can follow, and upper-body pressing or pulling waits, ideally for another day; if it has to be the same day, put hours between them. The table below sets this out swim by swim.
Whether endurance training holds back strength gains over months is a separate question; Running and lifting covers that research.
Can you do legs on a swim day?
Yes. Fatigue from endurance work tends to stay in the muscles that did it. Sporer and Wenger had 16 men do bench press and leg press 4, 8 and 24 hours after aerobic exercise: leg press repetitions were lower at 4 and 8 hours and back to normal at 24, and the authors concluded the impairment "appears to be localized to the muscle groups involved in the aerobic training".
For a swimmer, the muscles involved are mostly in the arms and shoulders. In 23 national-level swimmers aged about 15, swimming flat out on a tether for 30 seconds, the arm stroke supplied about 70% of front-crawl force in the boys and 67% in the girls, and the kick the rest. The authors read that as the kick playing an important role in short, all-out efforts. So the legs are not idle: a sprint set, a kick set or a long breaststroke session asks more of them than steady front crawl does.
- After an easy or technique swim, squats, hinges and lunges go ahead as planned.
- After a hard front-crawl set, legs are still the right choice for the gym: the shoulders are what the swim spent.
- After a kick-heavy set or a long breaststroke session, count your legs as having trained, and keep jumps or a maximal leg day for another time (our view).
What to lift after each kind of swim
The three sections above, in one table. Find the swim you just did, then read across to the kind of lifting you had planned.
| After this swim | Legs | Pressing or pulling | Full body |
|---|---|---|---|
| Easy swim | Fine. Fatigue tends to stay in the muscles that did the work (Sporer and Wenger). | Fine. Shoulder strength held even through a harder set just below critical speed, with rests between blocks (Dekerle and Paterson). | Fine, for the same two reasons. |
| Technique session | Fine, unless it was mostly kick drills: the kick supplied about a third of front-crawl force in all-out swimming (Morouço). | Fine. Slow drills sit well below the pace that tired the shoulders (Dekerle and Paterson; our view). | Fine, with the kick-drill caveat for the legs. |
| Hard set | Fine. The fatigue measured was in the shoulders (Dekerle and Paterson), and it tends to stay local (Sporer and Wenger). | Another day if you can. Shoulder strength fell by about a quarter (Dekerle and Paterson). If it has to be the same day, leave hours: sessions about seven hours apart still brought strength gains (Arsoniadis), and leg fatigue after aerobic exercise lasted up to 8 hours (Sporer and Wenger; our view). | Another day if you can, as for pressing or pulling. If not, leave hours: the legs are ready; the upper half is not (Dekerle and Paterson). |
Does swimming count as strength training?
Not in the sense the guidelines mean. The WHO recommends 150 to 300 minutes of moderate or 75 to 150 minutes of vigorous aerobic activity a week, and on top of that, muscle-strengthening activity involving all the major muscle groups on two or more days. The NHS lists swimming among its examples of vigorous activity, and its list of muscle-strengthening activities, from lifting weights and resistance bands to body-weight exercises, does not include it. It also says strength exercises should be done to the point where you need a short rest before repeating.
Swimmers' own research points the same way. In the studies the 2022 review gathered, dry-land strength training added to swimming may improve swimming performance more than swimming alone. If competitive swimmers, who spend hours a week in the water, still gain from the gym, a few swims a week will not stand in for it (our view). Swim for your heart and lungs, lift for strength, and count them separately.
What about swimmer's shoulder?
A review of 12 studies of competitive swimmers reported shoulder pain in 19.4 percent of masters swimmers aged 23 to 77; the far higher figures often quoted come from teenage and college-age squads, who trained many more hours a week. Pain that lingers after sessions, wakes you at night or changes your stroke is a reason to see a physio or a doctor, not only to rearrange your lifting around it.
A swimming and weight training schedule
Here is what the studies above look like in one week, built around two hard sets, a technique session and two easy swims. Legs go beside a hard swim, presses and pulls go a day after one, and the full-body session goes on an easy-swim day.
| Day | Pool | Gym | Why |
|---|---|---|---|
| Mon | Hard set | Legs: a squat, a hinge and a lunge, after the swim | Front crawl spends the arms, so the legs are free (Sporer and Wenger; Morouço). |
| Tue | None | Upper body: presses and pulls | A day after the hard set, not straight after it (Dekerle and Paterson; our view). |
| Wed | Technique session | None | Drills at low intensity leave the shoulders fresh for Friday (our view). |
| Thu | None | None | Rest: nothing at all. |
| Fri | Hard set | None | The week's second hard set, with nothing heavy for the upper body after it. |
| Sat | Easy swim, after the gym if you like | Full body | A day after the hard set. In one study, heavy lifting about 40 minutes before a steady set did not affect it, though blood lactate ran higher (Arsoniadis). |
| Sun | Easy swim | None | Below the pace that tired the shoulders (Dekerle and Paterson). |
Race HYROX as well? HYROX and swimming covers that pairing, and every other pairing is in Crossovers.
Add swimming under You: in SPORTS STACK, tap + ADD. It is listed as Swim. With Pro or during your trial, your coach then plans your strength and conditioning around your swims instead of on top of them. More in Add a sport or a class.
If you swim with a squad or book lanes on set nights, pick those weekdays under Fixed days on Swim's settings: each day you pick is one session a week. If your pool time moves around, Flexible lets the app pick the days around your other sports and classes. Add how long a usual swim lasts. The line at the top of that screen is about what swimming does to your body; with Pro or during your trial, that is what your coach is working around. More in Sport settings.
Exercises are shown as clean illustrations: the movement on a plain background, with nothing extra, so you see what to do at a glance. The team is exploring video and moving images. More in Exercise illustrations.
Shoulder sore after a block of hard sets? On Home, open LIMITATIONS, tap REPORT in the header, choose Injury and the shoulder, and set the slider from Cleared to Serious. With Pro or during your trial, your plan is rebuilt around what you report. Your coach is a training tool, not a medical service, and it tells you to see a physio or a doctor. More in Report an injury.