Can Heavy Be Hybrid? Why Bodyweight Changes Everything

As a 100kg athlete myself, I often wonder if I'm just making excuses for my poor performance when I start complaining about bodyweight when doing burbees or running.

However, there is scientific reasoning behind this. Running volume that seems to be manageable for a 70kg athlete can exhaust a 100kg athlete, both physically and neurologically. Body weight affects the mechanical load, metabolic cost, and nervous system fatigue associated with running. Certainly, having a larger mass can help lift heavier weights in certain exercises, but how does it impact running? Let's see some numbers.

1. Mechanical Load & Musculoskeletal Stress

Running is essentially a series of single-leg jumps. Every stride produces impact forces around 2.5–3× your bodyweight.

• For a 70 kg runner, that’s ~175–210 kg of force per step.

• For a 100 kg runner, it’s ~250–300 kg.

Now imagine a 10 km run — about 10,000 steps. The 100 kg athlete absorbs 30–40% more mechanical load than the 70 kg hybrid athlete. However this is only true if the step length is equal, it is higly likely that heavier athlete is also taller so withing same running distance there would be a little bit less steps and therefore the true difference would be around 25% range.

The difference can also be measured in watts. With the help of ChatGPT I calculated how many watts a runner needs to produce to complete a 5k in 20 minutes using the same formula that Garmin uses. The difference in total power output was even more significant: 43%.

In short: there is increased stress on joints, tendons, and the plantar fascia. Recovery is prolonged, even if both athletes experience the same cardiovascular effort during the run (though it's likely they don't, due to the significantly higher power output and the corresponding increased need for oxygen).

2. Metabolic Cost & Running Economy

The bigger you are, the more oxygen you consume in absolute terms. But endurance performance is defined by relative VO₂max (ml·kg⁻¹·min⁻¹).

• Heavier runners typically have lower relative VO₂max unless exceptionally well-trained.

• They also spend more energy per kilometer, especially at faster paces.

Put simply: same mileage = more calorie burn and metabolic stress for the heavier hybrid athlete. This means if you are heavier you can't use the same guidlines for nutrition, hydration etc. than your smaller training partners. Also notable the demand for energy is exponential, not lineral so insted of taking 1,5 gels for the run try taking 2 and see how that feels?

3. Central Nervous System (CNS) Fatigue

It’s not just the metabolic and mechanical stress, it is also the nervous system.

• Bigger muscle mass requires more motor units to fire at any given pace.

• This drives up CNS fatigue in heavier runners, slowing recovery of coordination, stride mechanics, and that springy “pop” in the legs.

In practice: A 70 kg athlete might wake up ready to squat the next day. A 100 kg hybrid athlete often feels heavy, sluggish, and needs extra recovery time.

As a 100kg runner my self I struggle to recover after high intensity runs. This is why I have to program them wisely.

Check list for Heavier Hybrid Athletes

1. Be smart with mileage! Swap some runs for rowing, cycling, or ski erg. (Less or no excentric work at all that seems to be the driving factor in CNS fatigue, for more about this check my other post about it here)

2. Focus on quality over sheer volume. Increase volume with clear plan and adjust if needed.

3. Prioritize recovery days, since both muscle and nervous system stress are higher.

4. Split more upper/lower and avoid same day training with running and lower body strength.

5. Try low impact cardio (row, bike etc.) combined with upper body stregth following days of heavy running.

6. Track recovery with tools like HRV, resting HR, or simple RPE. Feeling is more important than pace since it is subjective.

7. EAT A LOT! make sure you match your energy needs.