Most endurance athletes don’t avoid strength training because they’re lazy — they avoid it because they’re confused. Over the years they’ve heard the same mixed messages repeated over and over: Don’t lift heavy, you’ll get bulky. Just do high reps for muscular endurance. Strength is only for the off-season. The problem is that the research doesn’t actually support most of those claims, and the misunderstanding quietly limits performance more than people realize.
When scientists study strength training in runners, cyclists, triathletes, and Nordic skiers, the results are surprisingly consistent. The biggest improvements in endurance performance don’t come from light weights and high reps. They come from heavy, low-volume strength training — loads in the range of 80–90% of one-rep max, sets of three to six reps, long rest periods, and relatively low overall volume. This type of lifting improves neuromuscular efficiency, rate of force development, and movement economy. Athletes don’t suddenly gain excessive muscle mass; instead, each stride or pedal stroke becomes less costly in terms of relative effort.
That distinction matters because endurance racing isn’t limited by how much force you can produce. It’s limited by how efficiently you can produce submaximal force for a long time. Heavy strength work raises your force ceiling, which means the force required for race pace becomes a smaller percentage of your maximum. Coordination between muscle groups improves, tendons transfer force more effectively, and the same pace starts to feel cheaper. This is why research often shows better running economy or cycling efficiency without any meaningful change in VO₂ max or body weight. You’re not necessarily getting bigger or breathing differently — you’re simply moving more efficiently.
In contrast, light weights and high reps often feel productive because they create fatigue and a muscular “burn,” but they do very little to improve maximal force or neuromuscular efficiency. They rarely move the needle on economy at race intensities. That doesn’t mean lighter work has no value at all — it can help with accessory strength, mobility, or injury prevention — but it doesn’t build the foundation that allows endurance athletes to keep improving year after year. It adds fatigue without significantly raising the ceiling.
An important nuance here is the concept of being “strong enough.” Strength gains do not produce endless performance returns. Once an athlete reaches a solid baseline of strength, piling more weight onto the bar yields diminishing benefits. At that point, strength shifts from something you aggressively chase to something you maintain, apply, and express through power, stiffness, and elasticity. But if you never build that baseline — or you abandon it every season — you don’t stay the same. You slowly move backward.
This long-term erosion is what shows up most often in experienced athletes. They skip consistent strength work, dabble for a few weeks, then stop once racing begins. The cycle repeats each year, and over time baseline strength fades, durability declines, running economy worsens, and more endurance volume is required just to achieve the same results. Each new season begins from a slightly weaker starting point, making progress harder instead of easier.
The answer isn’t to lift heavy all year long. The answer is to periodize strength the same way you periodize endurance training. There are phases where maximal strength can be built more aggressively when overall training stress allows, followed by long stretches where it’s simply maintained with very low volume. As racing approaches, the emphasis often shifts toward power, stiffness, and durability rather than raw load. Strength isn’t a box you check once and forget — it’s a base you revisit, protect, and apply.
In the big picture, heavy strength training doesn’t replace endurance work; it supports it. Done correctly, it makes endurance training more effective, improves efficiency without unnecessary mass, and helps athletes continue improving rather than plateauing. Strength isn’t about lifting more forever. It’s about being strong enough — and not letting that base quietly disappear. If you train long enough, that foundation matters more than any single workout ever will.