Most runners I talk to are doing squats, deadlifts, lunges, and split squats. Great compound movements. Lots of muscle groups under load. That's exactly what we want.
But there's one muscle group that quietly does more work at the paces you actually run than almost anything else, and most people are either skipping it entirely or training it the wrong way.
The Research
A 2012 study out of the University of Melbourne used gait analysis combined with a detailed computer model of the leg's musculoskeletal system to figure out which muscles produce force at different running speeds. Nine experienced runners ran at four speeds, ranging from a 7:40 mile pace all the way up to sprinting. The researchers calculated exactly how much force each muscle produced at each pace and how each one contributed to pushing the body off the ground.
Citation: Hamner SR, Seth A, Delp SL. Muscle contributions to propulsion and support during running. Journal of Biomechanics. 2010.
What They Found
Running speed comes from two things: how long your stride is and how fast you cycle your legs. Speed equals stride length times stride frequency.
Here's what the data showed:
- Up to about a 3:50 mile pace, runners get faster mostly by lengthening their stride, which requires pushing harder against the ground.
- The calf complex, especially the soleus, is the dominant force producer at those paces. At a 7:40 mile pace, the soleus alone produced peak forces of nearly 8 times body weight during ground contact. The gastrocnemius added another 2.7 times body weight on top of that.
- Above roughly a 3:50 mile pace, the calves max out and the hip muscles take over. Glutes and hamstrings roughly doubled their peak force between the 3:50 and 3:00 pace ranges.
- The quadriceps barely changed across all four speeds. The big muscle most lifting programs prioritize is not the one driving your performance at training paces.
The takeaway: the calf complex is doing the majority of the heavy lifting at every pace most of us actually train at. And within the calf complex, the soleus, the deeper muscle, carries more of the load than the visible upper calf.
What This Means For Your Training
Most people, when I ask them what they're doing in the gym, tell me they're doing squats or deadlifts or lunges or other compound movements. That's awesome. Those movements target a wide variety of muscle groups under load, which is exactly what we're looking for.
The one thing that's almost always missing is heavy calf raises.
Here's where it gets interesting. Most runners who do calf raises got the prescription from Google after typing in "Achilles pain." They learned the two-feet-up, one-foot-down variation off the edge of a step, and they think that's enough load. In actuality, it's not. That's a rehab exercise, not a strength exercise. You need to progressively load the calves heavy, the same way you load every other muscle group.
The Two-Muscle Problem
Most people miss that the calf complex is actually two separate muscles.
The gastrocnemius is the one most people picture, the upper calf muscle you can see. The soleus sits deeper underneath it, and it's the one doing most of the work at your training paces.
Here's the key anatomical detail: the gastrocnemius crosses the knee, so straight-leg calf raises target it. The soleus does not cross the knee, so to isolate it you need to do calf raises with a bent knee.
The seated calf raise machine at the gym is perfect for this. If you don't have access to one, a heavy weight on your lap works just as well. I've done this at home with kids sitting on my lap. Works fine.
How To Apply It
Add dedicated heavy calf work 2 to 3 times per week. Treat it with the same intent as your squats and deadlifts: progressive overload, not bodyweight forever.
Train both calf muscles separately:
- Standing calf raises for the gastrocnemius
- Seated or bent-knee calf raises for the soleus
Aim for 3 sets of 6 to 12 reps with a weight that genuinely challenges you in the last few reps. If you can do 25 bodyweight reps without breathing hard, that's not strength work.
Don't drop the compound lifts. The hips and glutes still drive your faster paces, your hill work, and your race finishes. Keep deadlifting and squatting.
Get creative with load if you don't have gym access. A loaded backpack, weight on your lap during bent-knee raises, your kid sitting on your shoulders for standing raises. The principle is the same: enough resistance to push the muscle to genuine fatigue.
The Takeaway
The finding from this study is mechanical, not magical. Your calves are doing the most work at the paces you actually run. If you've been treating them like an afterthought, or doing the same bodyweight raises you got prescribed for Achilles pain three years ago, you're leaving a real chunk of performance on the table.
Especially as you age.
The good news: this is one of the most fixable gaps in most runners' training programs. Two to three sessions per week, progressive load, 15 minutes. That's it.