Strength Training for Endurance Athletes: Boosting Running Economy, Durability, and Performance
Can lifting weights really make you a better endurance runner? A new randomized trial by Zanini et al. (2025) says yes – and offers hard data to prove it. The study found that adding 10 weeks of heavy strength and plyometric training (twice per week) to a runner’s routine led to significant gains in efficiency and fatigue resistance . In simple terms, the runners who hit the weight room became more economical, more durable, and faster in the late stages of a run than those who did endurance training alone. Below, we break down the science-backed benefits and what they mean for both competitive and recreational endurance athletes.
Running Economy 101: What It Is and Why It Matters
Running economy (RE) is essentially your fuel efficiency as a runner – how much oxygen/energy you need to run a given pace. A runner with better RE uses less oxygen to run at the same speed, allowing them to go faster or farther on the same energy. Small improvements in RE can add up to big differences over long distances; even a 2% efficiency gain could shave a minute or more off a 10K time . The flip side is that RE usually worsens as you fatigue – after many miles, most runners’ form efficiency “drifts,” requiring more oxygen to maintain pace . This deterioration in RE over a marathon or long run can make the difference between finishing strong or hitting the wall. That’s why finding ways to improve RE – especially under fatigue – is so valuable for endurance performance.
Strength Training Enhances Running Economy (Especially When Fatigued)
It’s well established that strength training can improve running economy in a rested state . The new Zanini et al. study shows it also helps you stay economical when you’re tired – a concept known as improved “RE durability.” Before training, all runners saw their economy drop after 90 minutes of running. But after 10 weeks, the strength-trained group’s RE hardly deteriorated at all, whereas the control group got slightly less efficient. By the 90-minute mark of a run, the strength group was about 2% more economical than before, while the non-strength group was ~0.6% less economical . In fact, the strength-trained runners roughly halved the usual late-run increase in oxygen cost (their RE “drift” dropped from ~4.7% pre-training to 2.1% post-training) . Practically speaking, this means the athletes who lifted could maintain their pace with less energy expenditure than their peers when both were equally fatigued. Over a marathon, that kind of efficiency under fatigue can translate to maintaining pace in the final miles rather than slowing down.
After 10 weeks of strength training, runners became stronger and more powerful. Exercises like squats (above) were part of the program, building muscle force and tendon stiffness that improved running economy.
This improvement in running economy wasn’t just a lab measurement – the runners felt the difference too. The study noted that the strength-trained group had a lower perceived exertion by the end of the 90-minute run, meaning they didn’t feel as drained as the control group . In other words, heavy strength and explosive exercises made their usual running effort feel easier. Better running economy under fatigue (using less energy for the same pace) likely explains this – and it’s a huge confidence booster knowing you can hit mile 20 of a marathon feeling strong instead of crawling. For everyday runners, this could mean finishing long runs with energy to spare or simply getting more out of each training mile.
Greater Durability and Physiological Resilience
“Durability” in endurance sports refers to your ability to resist fatigue-related performance declines over time – essentially, how well you can hold up physiologically in a long race . The strength training group demonstrated markedly better durability. Their running form and efficiency stayed intact longer, indicating a boost in physiological resilience. In the study’s words, adding strength work “improved RE durability”, reducing how much economy deteriorated in the last 30 minutes of the long run . Meanwhile, the runners who did no strength training showed the expected decline in economy as fatigue set in. This suggests that strength training made the athletes’ bodies more resilient to the stresses of prolonged running, likely by delaying the onset of muscle fatigue and damage .
Improved durability isn’t just about numbers in a lab – it has real race-day implications. A more durable runner can hold their pace later into the race without faltering. They can also handle heavy training volumes with less breakdown. It’s telling that observational data show top performers often have superior durability compared to less trained runners . Strength training seems to cultivate this trait by hardening the body against fatigue. Runners in the strength group also finished the 90-minute runs with a lower perceived effort (RPE), as mentioned, which speaks to greater endurance comfort . For a recreational runner, that might mean feeling relatively fresh at mile 18 instead of completely wiped out. In short, strength work builds a tougher athlete – one who doesn’t fade as easily when the miles add up.
Stronger Finish: Better Time-to-Exhaustion and Late-Race Performance
One of the most striking findings was how strength training improved the runners’ high-intensity performance when fatigued. Immediately after the 90-min run, all participants ran at ~95% of their VO₂max (a very hard effort, roughly 5K race pace) until exhaustion – simulating a finishing kick or hard push at the end of a race. Before training, both groups could only hang on so long. But after 10 weeks, the strength-trained runners blew past their old limits. Their time-to-exhaustion at that near-max pace increased by 35%, whereas the control group actually saw a slight decrease (about –8%) . In practical terms, the strength group gained the ability to sustain an all-out effort for much longer at the end of a long run. This could mean sprinting the last quarter mile of a half-marathon to hit a PR or outkick a competitor, instead of tying up.
Such a large 35% boost in a lab TTE test is partly because time-to-exhaustion tests magnify changes (they’re very sensitive to fitness improvements) . But even if we translate that to real-world terms, it’s hugely meaningful. Research on runners and cyclists finds that strength training typically improves time-trial performance (like a set distance effort) by a smaller but still significant margin (on the order of 2–5% faster times) . That could easily be a minute or two faster over 10 km just from cross-training with weights. The key point: The strength-trained runners didn’t just preserve energy – they also amassed a bigger “anaerobic reserve” to tap into for intense bursts when it counts . For competitive runners, this can be the difference between holding pace in the final stretch versus slowing down, or between outsprinting someone versus getting outkicked. And for recreational runners, it simply means finishing strong and fast instead of the tank being empty. The data clearly support making strength workouts a staple if you want that stronger finish.
How Strength Training Boosts Endurance: Key Mechanisms
Why does pumping iron make you a better endurance athlete? It might seem counterintuitive – aren’t we supposed to just run more? It turns out strength training triggers a host of neuromuscular and biomechanical adaptations that translate to more efficient, fatigue-resistant running. Here are some of the science-backed mechanisms behind the improvements:
• Greater Muscle Strength = Lower Relative Effort: After strength training, your legs are capable of producing more force. Running at a given speed now uses a smaller fraction of your max strength, so each stride feels easier. This means you don’t have to recruit as many muscle fibers for the same output , delaying the point of fatigue. It’s like upgrading your engine – cruising at 8:00/mile is much less taxing on a V8 than on a four-cylinder. Stronger muscles also improve running form stability, preventing excessive breakdown in efficiency as you tire.
• Improved Muscle Fiber Recruitment: Strength training (especially heavy and explosive work) enhances how your nervous system coordinates muscle fibers. One benefit is the ability to delay the activation of less efficient, fast-twitch fibers until they’re truly needed . Normally, as slow-twitch fibers fatigue in a long run, your body starts roping in more fast-twitch fibers, which consume more energy for the same work. After strength training, runners can hold off this transition longer . In essence, you can rely on your economical slow-twitch fibers for more miles, and when your fast-twitch fibers do kick in, you’ve trained them to be more fatigue-resistant. This also ties into reduced muscle damage – fewer fibers need to be recruited prematurely, so there’s less overall strain.
• Stiffer Tendons = Springier Stride: One often overlooked adaptation is increased tendon stiffness, particularly in the Achilles tendon and other lower-limb tendons. Lifting heavy and plyometrics (jump training) cause tendons to adapt by getting stiffer and more elastic . A stiff tendon can store and release elastic energy more efficiently – acting like a spring in your stride. Every time your foot lands, the Achilles tendon stores energy and then bounces it back, reducing the work your muscles have to do. Strength-trained runners get better at this bounce. The study authors note that greater tendon stiffness can reduce the needed muscle shortening and improve the stretch-shortening cycle efficiency, directly improving running economy . Think of it as better shock absorbers and energy return with each step.
Heavy strength and plyometric training increase the stiffness and strength of tendons like the Achilles. A stiffer Achilles tendon works like a more efficient spring, storing and releasing energy with each stride to reduce muscular effort .
• Fiber-Type Shifts: Interestingly, strength training can induce changes in muscle fiber composition that favor endurance. Studies on endurance athletes have observed a shift from Type IIx fibers toward Type IIa fibers after strength programs . Type IIx are “fast-twitch” fibers optimized for power but relatively inefficient, whereas Type IIa are more of a hybrid fast-endurance fiber – they can produce force and sustain it more efficiently. Increasing the proportion of Type IIa means that when your Type I (slow-twitch) fibers start to run out of fuel late in a race, the fibers that take over are a bit more economical than before . This fiber-type conversion could be one reason the strength group’s running economy improved only in a fatigued state – those muscle changes become most relevant after the slow-twitch fibers get depleted .
• Neuromuscular Efficiency and Coordination: Strength training also enhances neuromuscular coordination – basically, your brain and muscles communicate more efficiently. One study cited in the paper showed that after just 5 weeks of strength training, athletes had a lower EMG (muscle activation) signal for the same output at the end of a 2-hour effort, compared to before training . In our context, the runners likely improved their ability to produce the required force with less muscle activation. This reflects things like improved intermuscular coordination (muscles firing in sync) and intramuscular coordination (recruiting just the right fibers). The result is less “wasted” energy and a smoother, more economical stride, especially when tired. It’s as if strength training raises your mechanical efficiency – you get more bang for each muscular buck.
• Glycogen Sparing: Running economy isn’t just about oxygen – it’s also about fuel (carbohydrates stored in muscles as glycogen). By delaying the recruitment of big fast-twitch fibers and improving efficiency, strength training can help you burn less glycogen for a given distance, effectively saving fuel for later in the race . The study hypothesized a glycogen-sparing effect: the strength-trained runners likely finished the 90-min run with more glycogen in reserve . This would directly contribute to their ability to keep pushing hard (since hitting the wall is often due to depleted glycogen). In fact, the authors noted that the improved RE durability probably left higher energy availability at the end of the run, which, coupled with lower effort perception, set the stage for the big boost in time-to-exhaustion performance . More fuel in the tank = a better kick at the end.
• Higher Anaerobic Work Capacity (W′): Heavy strength training can increase your capacity for high-intensity work – often denoted as W′ (W-prime) or D′ in exercise science (essentially the extra work you can perform above your aerobic threshold) . In cyclists, strength programs have been shown to bump up this anaerobic capacity even when aerobic fitness (VO₂max or threshold) didn’t change . In the running study, the authors suggest that the strength group’s huge gain in the exhaustive sprint test could be partly due to an increased W′ . Think of W′ as your “finishing battery” – strength training seems to make that battery bigger, independent of your aerobic engine. Combined with more preserved glycogen, this gave the runners a lot more juice to tap into for that final effort . So not only do you become more efficient aerobically, you also raise the ceiling of your anaerobic bursts.
These adaptations all work together to make a stronger endurance athlete. In short, strength training teaches your body to do more with less – more force with less muscle activation, more speed with less oxygen, more distance with less energy. It shores up weak links (like tendon strength and neuromuscular coordination) that pure endurance training might neglect. Importantly, the study’s program combined maximal strength lifts (for force production) with plyometrics (for explosiveness and tendon elasticity), which likely contributed to the full spectrum of benefits. This isn’t about lifting light weights a million times (which has minimal effect) – it’s about challenging your body with heavy loads and explosive moves to force these positive adaptations .
Why This Matters for Every Endurance Athlete
Whether you’re a marathon racer, a triathlete, or a casual weekend warrior who enjoys half-marathons, the findings are good news: strategic strength training can make you a better, more resilient runner. For competitive athletes, it offers a legal performance boost – better economy means a faster pace for the same effort, and improved fatigue resistance means you can actually use that speed at the end of a long race. It could be the edge that helps you set a new PR or outlast your rivals in the final stretch. Even elite marathoners, who already have superb running economy, stand to gain from any improvement in durability, as it could delay that late-race slowdown by a few critical miles.
For recreational and masters runners, the benefits are arguably even more important. Many non-elite runners struggle with “fading” in the later parts of races or long runs – exactly what strength training helps counter. Incorporating some lifting can help you finish strong instead of exhausted, making the endurance experience more enjoyable and less injury-prone. There’s also the bonus of injury prevention: stronger muscles and stiffer tendons mean your joints and connective tissues are better supported against the repetitive impact of running . In the study, the strength group even saw a small decrease in body fat (–11% fat mass) while maintaining the same weight , suggesting that concurrent strength and endurance training can improve body composition without causing “bulk.” This aligns with the broader evidence that runners don’t significantly gain muscle mass from twice-a-week lifting – instead, they gain functional strength and usually stay weight-neutral or slightly leaner . So the old fear that strength training might slow you down or make you too heavy is a myth; on the contrary, it can prevent slow-down by making you more efficient.
Perhaps the most compelling reason to embrace strength work is longevity. By improving your economy and resilience, you reduce the cumulative strain of running on your body. Over months and years, that could mean fewer breakdowns and more consistent training – a virtuous cycle that further enhances performance. It’s telling that many high-level coaches now consider strength training a staple for distance runners, not an optional add-on. The evidence is no longer just theoretical; it’s data-driven and quantifiable. As runners, we spend so much effort fine-tuning our aerobic engine – but we now see that tending to the “chassis” (muscles, tendons, neural systems) via strength training yields significant dividends.
Integrating Strength Training Into Your Routine
If you’re convinced to add some strength training to your regimen, the next step is knowing how. The runners in the study followed a supervised program of heavy lower-body lifts (like squats and single-leg press), explosive plyometrics (jump drills), and even some isometric strength moves for the calves . They trained twice per week, about 45 minutes per session, focusing on quality (high load or high power) more than quantity. This kind of program can be adapted to most runners with the guidance of a coach or a well-designed plan. Consistency is key – studies suggest a minimum of 6–8 weeks of regular strength workouts are needed to see measurable improvements in running economy , and benefits continue to accrue with longer programs. Aim for 2–3 sessions per week, hitting major muscle groups used in running (quads, glutes, hamstrings, calves, core), and include both heavy resistance exercises (4–8 rep range, once you’ve safely built up to that) and plyometric or explosive moves (like jump squats, box jumps, or bounds). Always prioritize good form and adequate recovery – for example, avoid intense leg lifting the day before a key hard run, and give yourself 48 hours if possible before a race or hard interval session .
If you’re not sure where to start, consider looking into training resources or programs that specialize in combining running and strength. For instance, the Running Hybrid Athlete program is one approach that integrates these principles into a cohesive plan, helping runners systematically build strength alongside endurance. The takeaway is that you want a program tailored for endurance athletes – one that targets strength and power without excessive muscle bulk, and aligns with your running schedule. By following a structured plan (or consulting a knowledgeable coach), you can safely progress your lifting routine and monitor the impact on your running times and fatigue levels. Most runners quickly notice that they feel “springier” and more powerful within weeks of starting strength training – and within a couple of months, you may well be setting new personal bests or at least feeling a lot stronger at the tail end of long runs.
Bottom Line: Strength training isn’t just for bodybuilders or sprinters – it’s a secret weapon for endurance athletes. The science shows that a properly executed strength program can make you run more efficiently, fatigue more slowly, and kick harder when it counts. By enhancing running economy, improving durability, and boosting high-intensity performance, lifting weights can ultimately help you run farther and faster with the same engine. For any runner looking to improve – be it to win races or simply to enjoy injury-free mileage – it’s time to embrace the iron. Your future marathon (or trail ultra, or Ironman, or weekend 10K) self will thank you when you’re powering through those final miles feeling strong and capable. So go ahead and add that strength day to your training week – your endurance will reach new heights, backed by the power of science and some well-earned muscle.
References: The information above is based on the findings of Zanini et al. (2025) and related exercise physiology research, illustrating the robust benefits of concurrent strength and endurance training for runners. All statistics and improvements noted (running economy gains, time-to-exhaustion changes, etc.) are drawn from peer-reviewed data in that study and others in the field for accuracy and credibility. Now it’s up to you to apply these insights to your own training – happy running, and happy lifting!
