Running physiotherapist Lydia McKay gets the same questions about strength training over and over, from clients and podcast listeners alike. Rather than answer them one at a time, she sat down to work through the most common ones properly, from why strength training matters in the first place to exactly how often you need to be in the gym.
The cup analogy
Lydia's core framework for thinking about running injuries is simple: imagine your tissue capacity, your muscles, tendons and bones, as a cup. The load you place on your body through running is the liquid you're pouring in. Running injuries happen when that cup overflows.
You don't want to fill the cup all the way to the top, either, since there's no margin left before a small bump, like an unexpected hill or a rough night's sleep, tips it over. The goal is a bigger cup, filled to roughly three-quarters, with room to spare.
Previous injuries shrink that cup. The research is clear that the more injuries you've had, the more likely you are to get injured again, which is exactly why building capacity through strength training matters even more once you've had a setback.
Why running alone doesn't build your cup
Different tissues adapt to training at very different speeds:
- Cardiovascular fitness adapts fastest, often within days to a couple of weeks.
- Muscles take around six weeks to show meaningful, detectable change.
- Tendons are slower again, up to 12 weeks for real adaptation, and they're also slow to tell you when they're unhappy, often not flaring up until 24-48 hours after a run, or months into a training increase. Dr Bill Evans covers the full physiology of these adaptation timelines in more depth, including why some of them take so much longer to build than others.
- Bone is the slowest of all, and running itself isn't a particularly good bone-building activity. It maintains bone density reasonably well, but it doesn't send a strong enough signal to make bone meaningfully stronger, unless you overdo it, in which case it breaks down instead. Physiotherapist Beau Tyrrell learned this the hard way with his own anterior tibial stress fracture, worth a read if you want to see what this looks like in practice.
That's the case for the gym: strength training gives muscles, tendons and bone a much stronger, more concentrated stimulus than running provides on its own, which means faster, more reliable adaptation.
What actually counts as strength training
Strength training means applying enough resistance to a movement that you create real stress on the muscle, tendon and bone, not just moving your body through space. The target intensity is roughly 7-8 out of 10 on a perceived exertion scale, or, more practically, having somewhere between one and three reps left in the tank at the end of a set.
A session that leaves your legs shaking and burning after 50 bodyweight squats isn't the same thing as a genuine strength stimulus, even though it feels hard. That "jelly leg" burning sensation is more a cardiovascular or muscular endurance response than true strength work, and it's also more likely to leave you with delayed-onset soreness that interferes with your next run.
Sets, reps and frequency
The basic formula that shows up consistently in the research: 3-4 sets of 6-12 reps for general strength. Beginners tend to sit toward the higher end of that range (10-15 reps) at a slightly lower intensity while they build familiarity and technique. As you get stronger, reps typically come down and load goes up, with 6-8 reps being a good target range for meaningful strength gains.
On frequency: once a week is better than nothing, but twice a week is the realistic minimum for general health and for maintaining gains you've already made. Three to four sessions a week is where you land in what Lydia calls the "golden zone" for muscle, tendon and bone adaptation. Tendon-specific research in particular tends to show the best results from four sessions a week, sustained for at least 12 weeks.
A useful approach if four sessions a week feels unrealistic long-term: pick a defined block, six weeks, three months, an off-season, and commit to the higher frequency during that window, then drop back to twice-weekly maintenance once you've built the capacity you were after.
Common questions, answered
Should I strength train before or after a run?
Before, if you have the choice. Running generates muscular fatigue, even an easy run, and fatigue interferes with your central nervous system's ability to recruit muscle effectively during a strength session. Training fresh gets you the most out of the session. The exception: never strength train immediately before a speed session, since any residual fatigue in that context raises injury risk.
Can I strength train on sore muscles?
Yes, and it can genuinely help. Light strength work increases blood flow, which helps clear the metabolic waste products responsible for soreness in the first place. Reduce the intensity though, higher reps, lighter load, rather than pushing for a personal best while you're already sore.
Can I train at home with just bodyweight?
You can start there, but bodyweight training has a ceiling. Once you're strong enough that bodyweight exercises no longer challenge you, you'll need external load (dumbbells, a barbell, resistance bands) to keep producing a genuine strength stimulus. Very advanced bodyweight movements like pistol squats exist, but they tend to challenge mobility and stability as much as pure strength, and don't transfer to running as directly as a well-loaded squat or hip hinge.
Is one session a week enough for tendon health?
Generally no. Tendon research consistently points to needing at least two sessions a week to maintain gains, with four sessions a week over 12+ weeks showing the best adaptation in the literature.
How do I know if I'm working hard enough?
Track reps in reserve. If you could grind out one to three more reps if you absolutely had to, you're in the right zone. Occasionally (with good form and ideally some supervision) testing a lift to genuine failure helps calibrate what your real capacity actually feels like, since most people underestimate how much they have left.
The four exercises every runner should be doing
According to Lydia, these four movement patterns cover the essentials:
- A squat pattern (knee-dominant) - goblet squat, back squat, split squat, leg press, whichever variation suits your equipment and experience.
- A hip hinge pattern - deadlift, RDL, hip thrust. Anything targeting the posterior chain.
- A unilateral (single-leg) exercise - Bulgarian split squats, lunges, step-ups, single-leg RDLs. Important for evening out asymmetries and building the stability every runner relies on.
- A single-leg calf raise - the calf works extremely hard during running, and single-leg loading gets far more out of the exercise than doing it double-legged.
Beyond those four, plyometric or reactive strength work (box jumps, depth drops, squat jumps) is close to essential for tendon and bone stimulus, typically done for low reps (3-5) across a few sets. Anything else, core or anti-rotation work, specific accessory exercises, is best individualized to your own injury history and goals rather than applied generically.
Does powerlifting-style training affect running economy?
Yes, positively. Because powerlifting is fundamentally strength training (just at the very low-rep, high-load end of the spectrum), it produces the same running economy benefits as any well-structured strength program: better neuromuscular efficiency, stiffer tendons, and typically improved running form as a result. The main caution is scheduling, training to failure regularly can tax your central nervous system enough to interfere with high-quality speed sessions, so it's worth being deliberate about which days carry the heaviest lifting versus the hardest running.
One practical gap to watch for: a conventional powerlifting program (squat, bench, deadlift) doesn't include single-leg work or calf raises. If that's your primary strength training style, it's worth adding those back in specifically for running.