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Battling Injury & The Law of Diminishing Returns

By Caitlin Alexander, CAFS

Disclaimer: The following article pertains to my experiences with endurance training and what I’ve learned through the process; it does not apply to everyone. All opinions expressed are solely my own.

My Training Saga
My average weekly mileage when I qualified for Boston last spring was 27.5 miles. My longest run in training for Boston this spring was 18 miles.

There was once a point in my training where I felt the need to run upwards of 40-50+ miles a week, and I had myself convinced that I had to at least hit the 20 mile mark in my long runs. Yet, I would frequently make it to the starting line injured, and my race performances were lackluster.

It took many years of marathon training to learn that I don’t have the biomechanics nor durability to sustain upwards of 50-60+ miles a week. My body starts to break down. I’m also not a professional athlete, and I’m not looking to win any marathon. And I’m A-okay with that.

With each season that passes, I become more aware of my body and how important health and wellness is. It’s not simply about being “fit”, as one can be simultaneously fit and injured. What I’m referring to is whole body health — healthy heart, healthy mind and healthy tissues.

Rest and recovery are the most important ingredients in any training regimen. It’s during these passive periods that training adaptations manifest.

Running has always been a “two steps forward, one step back” journey for me, and I’ve learned what my limits are and how to work around them. That’s part of the reason why I got into the sport of triathlon, where I have two other sports to fall back on when my body is telling me to hold back with the running. An important part of excelling at the marathon distance (or any other endurance event) is experience: experience with both training and racing and really knowing how to read your body.

If I’ve learned anything from my years of endurance training, it’s how much to stress my body, when, and when to back off. Each one of my runs now has a purpose, and I often replace some of my runs with cycling to reduce impact, maintain cardiovascular fitness and build strength (Heartbreak Hill here I come!). For the beginners I coach, I always stress that less is more.

So when athletes tell me they need to do a 20-22 mile long run for their marathon training, I always ask, why? Are you attempting to run a 2:30 marathon? Okay, that’s fair. If not, then why? Do you need that psychological confidence knowing that you hit that 2-0 mark? I know, I’ve been there. And I ran my slowest marathon times while battling injuries.

The Law of Diminishing Returns
The Law of Diminishing Returns in economics states that in all productive processes, adding more of one factor or production, while holding all others constant, will at some point yield lower incremental per-unit returns. This can be applied to running in that, at some point in training, a continuously increasing volume will start to yield a negative training adaption. Gains at higher training levels will be less than those obtained at lower levels. This principle is illustrated in the figure below where we see that doubling training at a higher level yields a lesser increase of potential.

Diminishing returns as training mileage is increased.
Source: Daniels, Jack. Daniels’ Running Formula. New York: Human Kinetics, 2004

Although the curve looks different for every individual, the general trend remains the same. The principle of diminishing returns is also directly proportional to the principle of accelerating setbacks where, as training volume is increased, the risk of setback due to acute injury or overtraining is also increased.

Why? Fatigue causes your form to break down. I guarantee that at that 19-mile mark, your form will not be as fresh as it was at mile 1. Furthermore, that 20+ mile investment will yield a longer recovery period, especially if the runner is a novice at the distance. Think about it: If an athlete is training to run a 4:00-4:30 marathon, a 20-mile run would equate to almost three and a half hours of running, which can take a huge physiological toll on the body and put that athlete at a higher risk for injury.

So Is The 20-Mile Long Run For You?
The long run attracts more attention than any other component of marathon training, almost serving as a status symbol or bragging rights. For fairly new runners (or those new to the distance), a 20+ mile run can take a big toll on the body. Sure, some runners have the biomechanics and durability to sustain high weekly mileages, and that’s fantastic. For elite and professional athletes, this is standard, but running is essentially their full-time job.

For the average weekend warrior, it is a fine art learning how to balance the demands and stresses of training with that of work and personal life. Stress from life outside of training can also yield an increase in cortisol in the body, a catabolic hormone that can break down tissue and increase risk of injury.

My advice? Be smart and listen to your body. For me, my body can handle 30-35 miles of running per week max. That’s not a lot for marathon training, but it got me a Boston Qualifier.

The takeaway? Quality over quantity.

Caitlin Alexander is a jack-of-all-trades at Finish Line, working both at the front desk and as a physical therapy aide. She is a Level I USAT-certified triathlon coach and has been part of the Empire Triathlon Club coaching staff since 2015. Additionally, she holds a Certification in Applied Functional Science from the Gray Institute.

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