Muscle Damage and Running Economy (Part 2)
"It's the economy, stupid."
The implications of muscle damage during endurance events presents a paradox - the very act of racing progressively reduces our ability to maintain race pace. But it's not as simple as just muscle damage leads to reduced running economy. While the data we collected in our research project described in Part 1 demonstrate acute effects of muscle damage, the real-world implications during long races like marathons and ultramarathons are more complex and potentially performance limiting.
During a marathon, muscle damage accumulates through the race. Unlike the controlled laboratory setting where damage is induced through a single session of eccentric exercise, race-day muscle damage is compounded by multiple factors: repeated eccentric loading from thousands of footstrikes, environmental conditions, terrain, and the high-intensity nature of racing. By mile 20, when many runners hit the proverbial "wall," they're not just fighting glycogen depletion - they're battling significant muscular deterioration. Their reduced running economy then requires even more energy to maintain any given pace. I assume as economy deteriorates over time, there will be an exponential increase in energy requirements, just as their running low on substrate (glycogen/glucose). This "double-whammy" contributes to the overwhelming wall of demands placed on the body.
The phenomenon of increased cost of running is demonstrated well in this study from Howe et al. This figure demonstrates, over time, the cost of running increases (decreased economy).
 |
| Howe et al. 2021 |
The impact could become even more pronounced in ultramarathons. Consider a 100-mile trail ultra: runners face repeated eccentric loading from descents, often on technical terrain, while managing fatigue and varying intensities. As muscle damage accumulates, runners require more oxygen to maintain their pace, leading to increased perception of effort and forcing them to increase their effort, slow down and/or alter their running mechanics.
This progressive nature of muscle damage during races could create a sort of positive feedback loop. As running economy decreases, more energy is required to maintain pace, accelerating fatigue. Fatigue leads to deteriorating form and economy, potentially causing more muscle damage, further increasing energy requirements and so on...
If muscle damage is so detrimental to running performance, what can we do to prevent or delay damage and preserve economy?
I maintain that the best training for running is running. If you were to take average Joe off the couch and have him run a 5K, he'll be a lot more sore (experience more muscle damage and inflammation) in the following days than someone who routinely runs an hour every day. The runner has adapted to training - and is able to handle the eccentric load. To an extent, training improves your ability to prevent or delay muscle damage. Greater volumes of training may further improve the runner's "durability." Perhaps this is one benefit of "high volume" training. I'm not aware of any research on the topic of training volume and muscle damage... but generally, elite marathon and ultra marathon runners accumulate relatively high volumes of run training.
Specifically addressing muscle damage - runners can train for the eccentric loading by running downhill. You've likely seen or done hill training at some point. Uphill intervals are often used to add resistance to running... There's an increase in metabolic demand when running hard uphill. When running downhill, the emphasis is not placed on the metabolic system, instead the increased eccentric loading places more stress on the musculoskeletal system. Downhill running should be done on a gentle grade 2-4% so that running form can be maintained. And you should be careful not to do too much... this type of training places a greater eccentric load on the body - which is the whole point, but with increased stress comes the need for reduced volume and/or greater recovery times.
Ultrarunners incorporate specific downhill training sessions not just to improve descending skills, but to build muscular resistance to damage. This represents a shift in thinking from simply training for cardiovascular fitness to training specifically for mechanical durability.
Other training methods involve strength and plyometric training. These types of training have shown a lot of promise in improving running economy. By targeting muscle groups with eccentric loading, we can improve their ability to handle eccentric contractions from running.
Strength and plyometric training may include:
These exercises target the primary muscle groups involved in running: the quadriceps, glutes, plantar flexors, hip flexors and hamstrings.
The next frontier in endurance performance might not be about getting faster, but about staying economical longer. As we better understand how muscle damage affects running economy during races, we can develop more effective strategies to preserve it - potentially revolutionizing how we approach both training and racing in endurance events.
Oh... But what about shoes? Can these high-stack-height, highly cushioned, carbon-fiber-plated shoes delay muscle damage and preserve running economy?
Comments
Post a Comment