Endurance Programming Isn’t Complete Without Strength (Part 1)

In the past, the endurance world treated the weight room like enemy territory (thankfully, that’s changing). Too much muscle? You're hauling dead weight. Time under the barbell? That's time you could be logging miles. In truth, running, cycling, and swimming are aerobic sports, so what good does strength do?

A whole bunch, as it turns out.

The Science Across Sports: Runners, Cyclists, and Swimmers

Recent research makes an undeniable case across virtually every endurance discipline.

Runners: A 2024 meta-analysis examining strength training methods in middle- and long-distance runners found that heavy load training (≥80% 1RM), plyometrics, and combined methods all improved running economy (how efficiently you use oxygen at a given pace). Critically, these improvements occurred at different speed ranges: plyometrics helped at slower paces (≤12 km/h), while heavy strength training improved economy at higher speeds (8.64-17.85 km/h), particularly in athletes with higher VO2max values (Llanos-Lagos et al., 2024).

Even more compelling, a 2025 randomized controlled trial with well-trained male runners (VO2max ~59 ml/kg/min) found that adding strength and plyometric training twice per week for 10 weeks didn't just improve running economy in fresh athletes, it improved "running economy durability," meaning economy held up better during prolonged efforts. After an intense 90-minute run in the heavy intensity domain, the strength-trained group increased their time-to-exhaustion by 35%, while the endurance-only group actually decreased by 8% (Zanini et al., 2025). You don't just get faster. You get more resilient.

Cyclists: A systematic review with meta-analysis published in 2025 examined heavy strength training (≥80% 1RM) in 262 endurance cyclists. Training enhanced cycling efficiency, increased anaerobic power, and improved overall performance, with no negative impact on aerobic markers like VO2max (Llanos-Lagos et al., 2025).

Swimmers: While endurance athletes on land have been a bit slower to adopt strength work, competitive swimmers have known for years that dry-land resistance training matters. A 2025 systematic review and network meta-analysis found that combining water-based training with dry-land resistance training was most effective for improving sprint swimming performance, more than aquatic training alone (you might make the argument that sprint swimming is not an “endurance” sport and to that I’d say, I agree, but I’d venture to argue this would hold up in longer endurance swims). The dual stimulus of land-based mechanical loading plus aquatic resistance provided complementary neuromuscular adaptations that neither approach achieved independently (comparative effectiveness meta-analysis).

The pattern is consistent: strength training improves performance across endurance sports through mechanisms that pure endurance training cannot replicate.

Why Do Endurance Athletes Still Avoid the Weight Room?

While I haven’t found so much research on the topic, there has traditionally been some fear of gaining muscle mass. Endurance athletes (in my experience) worry that strength training will pack on unwanted bulk that they'll have to drag through 26.2 miles or 112 miles on the bike. Hopefully, the above convinces them that this fear is unsubstantiated. Importantly, for most endurance athletes, strength gains should come primarily through neuromuscular adaptations. Here, the nervous system gets better at recruiting existing muscle fibers, rather than significant hypertrophy (where one might add tons of muscle mass).

The interference effect. Research on concurrent training (combining endurance and strength work) shows that concern for this combined training negatively impacts endurance gains is relatively unfounded. A 2024 meta-analysis examining sex differences in concurrent training found that while males showed small interference effects for lower-body strength adaptations, there was essentially no interference for females. VO2max improvements were maintained across both sexes when strength and endurance training were combined in trained and highly trained athletes (Huiberts et al., 2024).

My thoughts: if you're already running 70 miles (~113 km) per week, adding heavy squats every day will probably compromise strength gains. But you're most likely not doing that. And the performance benefits for endurance still vastly outweigh theoretical losses in maximal strength that you weren't chasing anyway.

Time scarcity. "I don't have time to lift and run/ride/swim 10-15 hours per week." Fair. But consider this: a 2025 umbrella review of systematic reviews examining strength training in endurance athletes found that programs with as little as 2 sessions per week, performed for 6-12 weeks, produced meaningful improvements in running economy, time to exhaustion, and anaerobic capacity (Ramos-Campo et al., 2025). That investment may improve your race performance more than adding another 90 minutes of Zone 2 work.

Stay tuned for part 2, we’ll dive into how to program strength effectively for endurance athletes!