Runners Are Told to Lift Heavy Weights: What Does that Actually Mean?

The push for runners to lift heavy weights is nothing new. A decade ago, marathoners would attend Crossfit for strength training. As was the case then, this advice can feel simultaneously vague and overwhelming: how heavy is heavy, and how exactly do you manage that while also running high mileage and hitting paces on hard workouts?

This article will explore the nuance of what heavy lifting actually looks like in a running plan – and how you can implement it, without feeling exhausted and sore all the time.

Why does lifting weights benefit runners?

Firstly, it’s worth clarifying: if running performance is your goal, weight lifting is secondary to running in your training plan. While weight lifting can enhance running economy, it is only if run training has set the foundation. (If you are training for health, you may strike a more even balanced of running and lifting.)

Strength training may confer moderate performance benefits to running economy and durability. Again, you need a run training to develop these, as well as other performance determinants. Research suggests that strength training really won’t change your VO2max or lactate threshold.

Running economy is your body’s fuel efficiency: how much oxygen you need to use to sustain any submaximal pace. When you improve your running economy, your oxygen cost at submaximal paces is lower – which leads to better performance in long distances from the 5K to ultra marathon.

A 2024 meta-analysis demonstrated that high-load resistance training (≥80% of your 1RM) and plyometric training result in small to moderate improvements in running economy. The magnitude of improvement was dependent on pace and intensity, with plyometrics being more beneficial for slower paces and high-load resistance training for faster, high-intensity running.

For races lasting over 90-minutes, strength training may also improve your durability. A 2025 randomized controlled trial with a sample size twenty-eight well-trained runners found that those who completed a 10-week supplemental heavy-resistance and plyometric training program maintained their running economy better in a tired state (after 90 minutes of running between their first and second lactate threshold, or roughly between marathon and half marathon/10K pace).

Beyond the potential running economy improvements, resistance training confers other benefits for runners. A 2018 study demonstrated improvements in bone mineral density in male distance runners who did any sort of resistance training over the previous three years. (While the study didn’t have female participants, women aren’t an entirely different species. While estrogen and other hormones impact bone health, bone mineral density improves under loading for female athletes too.) The better one’s bone mineral density, the lower the risk of bone stress injury. (Important note: you must be in an energy balance too.)

The research isn’t definitive on whether strength training impacts the risk of soft-tissue injury. It certainly doesn’t create complete protection; runners who lift can still get injured. However, resistance training may be protective against strains and tendinopathies, which are treated using resistance training.

As with many things in running, there’s a curve. Some resistance training is beneficial for performance and health. Too much – whether through volume or intensity – may be detrimental.

Runners shouldn’t lift to failure

A common mistake that runners make is mistaking that lifting heavy means always lifting to failure. While this technique is commonly used in bodybuilding programs, lifting to failure can impair running performance on following days’ runs. Lifting causes muscle breakdown; too much muscle breakdown can impair form and force production on runs for a day or two following.

Additionally, training to failure is not necessary for muscle growth (hypertrophy). A 2022 meta-analysis demonstrated no statistically significant difference in hypertrophy when lifting to failure compared to not. Lifting to failure was not necessarily detrimental, but it wasn’t necessary. Very highly trained lifters may need to work closer to failure to achieve greater hypertrophy, based on the meta-analysis, but that is a different demographic than most runners who lift.

Even if your goal is muscle growth, you don’t need to lift to failure. As mentioned in one of the studies before, ≥80% of 1-rep maximum loads elicit improvements to running economy. Some people misinterpret, thinking it means lifting so heavy that they strain and injure themselves. (No, I’m not kidding, I got angry comments of this nature on blog posts before).

In resistance training theory, there’s a concept of %1RM-Repetition Relationship. It’s similar to workout dosing in running, where moderate efforts are held for longer reps and high-intensity intervals are held for shorter reps. 80% of 1RM allows for 8 repetitions per set. 85%1RM can be performed for six reps.

That’s certainly not to failure – nor is it even maximum loading. You don’t need to go out and lift super heavy for three reps.

Additionally, you don’t need to perform 1-rep max testing. (It is strongly discouraged to do any 1-rep max testing without a spotter and guidance.) For this recommended range, you can load your lifts so that you have 2-4 reps in reserve after each set. For example, if you are doing three sets of 8 goblet squats, you feel like you could do a couple more reps with good form after you complete all 8 squats.

Then, pay attention to how you feel in the following days. Are you so sore that you are unable to complete your prescribed runs? Scale back the weights next time.

How many reps should runners lift?

Years ago, the belief was that runners should lift for endurance. Endurance lifting schemes involve high reps using low weight, such as 2-3 sets of 15 reps. The research has progressed us past this point. However, pendulums swing, and many runners too this to mean very heavy lifting and Crossfit style workouts.

Instead, most runners will benefit from lifting 3-4 sets of 6-8 reps. (Right at that 80-85% of 1RM range discussed above.) This approach is often called a hypertrophy rep scheme, but don’t let the name intimidate you. Unless you’re mega-dosing protein and creatine, you won’t bulk out. Endurance training has an interference effect that makes it much, much harder to gain muscle mass, even as your strength and motor unit recruitment improves.

Some exercises will use higher reps to produce a hypertrophy effect. For example, the soleus muscle – that sneaky deep calf muscle responsible for both force production and various shin injuries – is predominantly slow-twitch in its muscle fiber typology. Especially with the nature of soleus exercises (bent leg), you may need to 10-12 reps to adequately strengthen it.

Importantly, if you are newer to resistance training, you will want to start with lighter weights to ensure you master your form first.

Don’t compromise form in the name of lifting heavy

Now, that all said: lifting heavy doesn’t mean lifting as heavy as possible. Similar to running: you aren’t all-out sprinting your intervals and straining through them with poor form. You are pushing appropriately hard without your form falling apart. Lifting is the same: pushing appropriately hard with good form.

If you want to optimize adaptation and decrease your injury risk for lifting, you need to prioritize proper form and a full range of motion. Lifting too heavy compromises form, which makes the lift less effective – and more risky for tweaking your back, knee, or something else.

Signs you are lifting too heavy on your strength days include:

• If you are straining against a weight.
• If you are unable to go through the full range of motion.
• If you are unable to complete the prescribed reps with good form.
• If a movement causes pain during or after.

If ever in doubt, consult a strength and conditioning expert for guidance on form.

Stop making your lifts into cardio

One crucial component of a lifting program are the rest intervals. You don’t just breeze through one set and exercise to the next without stopping. The goal certainly isn’t to keep your heart rate up – that’s cardio, not strength training. (And yes, certain programmings with weights can have a cardio stimulus.)

Resistance training uses different energy pathways than running. Lifting weights relies predominantly on your phosphagen and fast glycolysis energy pathways – both of which are anaerobic. These energy pathways support the very high output of a lifting exercise, but fatigue very quickly. Rest periods allow the phosphagen concentrations to rebound, which then allows you to continue to lift to the same intensity and quality in the next set.

The heavier the lift and the more muscle groups involved, the more rest you need in between sets. Typically, hypertrophy rep schemes use 60-90 sec rest breaks, although you may rest up to 2 minutes after multi-joint movements such as squats or deadlifts.

As noted above, supersetting allows more rest between each movement while being time efficient. Let’s say you superset a goblet squat and a bench press, with 60 sec rest after each superset. If it takes you 30 seconds to complete each exercise, and then you rest 60 sec after each superset, you have 90-sec rest between sets of squats.

Accessory movements such as band work and bodyweight core work don’t require as much rest, typically ≤30 seconds between sets.

Additional References

• https://www.sciencedirect.com/science/article/pii/S2095254621000077
• PMID: 34822137
• PMID: 38509414
• Haff & Triplett. (2016). Essentials of Strength and Conditioning. 4th edition. Human Kinetics.