Mechanical vs. Metabolic Load

Summary

This video is not a sports match; it’s Lionel Sanders’s explanation of how training stress differs across swimming, cycling, and running, and why he now uses the treadmill to help manage injuries.

Three kinds of training stress

Sanders separates training load into three types:

• Metabolic stress concerns the body’s energy systems and can be tracked with measures such as lactate.
• Cardiovascular stress is commonly monitored through heart rate.
• Mechanical stress is the impact and strain placed on muscles, tendons, ligaments, and bones.

Swimming and cycling can create substantial metabolic and cardiovascular effort with comparatively little impact. Running, especially outdoors, combines hard effort with repeated shock loading, making it more difficult to recover from and, in his view, easier to overdo.

Sanders reflects that he underestimated this distinction for years. He says he had a long stretch of resilience before injuries became a serious problem and regrets not recognizing the value of managing mechanical load sooner. Impact isn’t inherently bad—it can be useful in moderation—but it takes time and consistency to recover from, and age can make that harder.

Running on an indoor track

Sanders recalls a winter in 2013 in Dundas, Ontario, when he slipped on a snowy trail about 10 km from home and badly twisted his ankle. After limping home, he spent three months running on an indoor track because he feared another injury would disrupt his training.

He says that period led into his best running result: after the track block, he raced the 30 km Around the Bay event. In his experience, the softer track reduced impact enough for him to train hard and consistently.

Using the treadmill to manage impact

Sanders presents the treadmill as another way to separate running effort from some of its pounding. In a run he describes as his first in eight weeks without support, the final seven minutes felt difficult. Still, he argues that a tough cardiovascular and metabolic workout doesn’t have to leave the joints feeling as beaten up.

He uses a Stride sensor to track speed, a heart-rate monitor, and perceived exertion. Runners can also increase speed or incline if the workout feels too easy.

His point isn’t that every run should be on a treadmill. Rather, athletes who struggle with injuries can use it to build fitness and consistency while reducing impact. He argues that this trade-off may be worthwhile even though treadmill running is less specific to racing outdoors. He closes by saying he wishes he had understood the idea before spending 2.5 years dealing with injuries.

Presenter and references

• Presenter: Lionel Sanders
• Sources and references mentioned: Norwegian threshold-training approach; The Endurance Paradox; Stride sensor; heart-rate monitor