Guides · Strength
The Science of Getting Stronger
Progressive overload, sets and reps — and why endurance athletes should lift.
2 min read
Progressive overload
Strength training works on the same principle as endurance training: give the body a challenge slightly bigger than it's used to, let it recover, and it adapts. In the gym, that means gradually doing a little more over time — a bit more weight, an extra rep, or an extra set.
The key word is gradually. Small, steady increases beat big jumps every time.
Sets, reps and how heavy
A useful guide is to finish each set feeling you could have done two or three more reps with good form. That's hard enough to drive progress, without grinding out ugly reps that raise the risk of injury.
Lower reps (about 3–6) with heavier weights mostly build strength. Moderate reps (about 6–12) build both strength and muscle. Higher reps build muscular endurance. All of them work if you push close to that two-or-three-in-reserve point.
Rest matters too: longer rests (2–3 minutes) between heavy sets let you lift more, which is why strength programmes like 5 × 5 use them.
How much is enough?
Research suggests that around 10 hard sets per muscle group a week works well for most people, split over two or more sessions. Beginners can make excellent progress with much less — two full-body sessions a week is plenty to start.
Consistency over months matters far more than any particular programme.
Why runners, cyclists and swimmers should lift
Strength training can make endurance athletes more economical — using less energy at the same pace — and helps tissues cope with the repetitive load of running, riding or swimming. For runners in particular, single-leg strength and strong calves and hamstrings are especially useful.
It won't make you bulky. Building lots of muscle needs a lot of food and a lot of lifting volume; two short sessions a week alongside endurance training mostly makes you stronger, not bigger.
Fitting it in
Lift on easy days or after an easy session, not before a key run or ride. Keep it to 30–45 minutes. In the weeks before a race, cut back to one shorter session to stay fresh.
In Exersio
Start › Gym has ready-made routines — Full Body A and B are the place to begin, and For Your Sport has sessions for runners, cyclists, swimmers and triathletes. As you log sets, last time's numbers show in grey so you can beat them, and Performance shows your gym bests and strength progress.
General guidance, not medical advice. If something hurts or you have a health condition, speak to a doctor or physiotherapist.