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Strength Training for Endurance Athletes Part I - The Science

June 2, 2017


What comes to mind first when you think of the the phrase “strength training?” Do you think of big, bulky athletes like football players, baseball players, bodybuilders or powerlifters? What about the leaner, typically scrawnier athletes like swimmers, cyclists, and runners? When it comes to strength training, there are benefits to be gained for all athletes, both strength/power-based athletes as well as endurance athletes.


In this two-part series, I will cover 1) What the research tells us about strength training for endurance athletes and 2) some practical strength training recommendations that you can begin applying to your own training as an endurance athlete.


Before I begin discussing the effects of strength training on endurance athletes, it is important do have an understanding of the three main factors that determine endurance performance (1):


1. Maximal Aerobic Power (VO2 Max)


This is the maximal amount of oxygen that your body can take in and utilize for energy production. A higher VO2 max has been very well documented to be associated with better endurance performance. As VO2 max increases, so does your ceiling for aerobic energy production, which is key as an endurance athlete.


2. Lactate Threshold


In simple terms, this is essentially the percentage of your VO2 max at which you begin to accumulate exponentially larger concentrations of a metabolic by-product called lactic acid in your blood. Lactic acid then breaks down to formthe molecule lactate and a hydrogen ion. It is the rapid accumulation of hydrogen ions in the bloodstream and in the muscles which leads to fatigue due, NOT lactic acid. The lactate threshold is very closely related to your body’s ability to exercise at primarily an aerobic intensity, and going beyond this lactate threshold is essentially the point at which you begin to rely more heavily on anaerobic metabolism to produce energy for exercise, of which the metabolic by product is lactate. Being able to exercise at a higher percentage of your VO2 max before crossing over your lactate threshold means that you can exercise at a higher intensity/pace for longer periods of time without crossing the point at which you begin fatigue due to the rapid accumulation of lactate.


3. Exercise economy


The economy of exercise is most easily defined as the energetic cost of performing a given exercise velocity. In other words, it is the amount of energy (calories) you expend in order to move at a certain rate. For example, a runner that can run at 8.0 mph while expending 100 calories per mile is more economical than another runner moving at 8.0 mph, but expending 120 calories per mile. There are a variety of factors that affect your economy, but essentially, as your exercise economy increases, you can maintain exercise velocities with less effort.


So, when it comes to the effects of strength training on endurance performance, there seems to be little research indicating that this type of training directly affects your VO2 max or your lactate threshold. Strength training seems to have its biggest impact on your exercise economy (2). The exact type of strength training that one performs has the potential to impact the outcome experienced, but in general, strength training has the potential to improve endurance performance through the following mechanisms (2):


1. Increased tendon stiffness of the muscles


When a muscle contracts, the force that is generated in the muscle fibers are transferred through the tendon that attaches the muscle to the bone. Stiffer tendons are essentially better able to transfer this force production to the bone with each contraction, thereby resulting in a more efficient exercise economy.


2. Improved maximal strength


You may not think that improved strength will benefit an endurance athlete, but it can. As an endurance athlete, you typically perform submaximal muscle contractions when you swim, cycle, or run. As your maximal strength increases, those same relative submaximal muscle contractions begin to feel easier and cause less fatigue as your muscles are working at a lower percentage of their theoretical maximum. This is accomplished through fewer motor units being recruited during submaximal muscle contractions. When a muscle contracts, it recruits the number of motor units required to do the job. When your muscle fibers become capable of generating more force, less of these motor units are needed to produce the same outcome.


Both of the mechanisms stated above typically lead to an improved exercise economy (2), which subsequently allows you to move at the same relative submaximal velocities without getting quite as fatigued as you would if you were less economical. Think of it in terms of the endurance sport that you typically partake in. If you are a runner, becoming more economical will allow you to run at the same speeds you are used to running at, but with slightly less effort. If you are a cyclist, you will be able to cycling at the same speeds you are used to cycling at, but with a lower perceived effort. The same can be said for swimming or cross-country skiing.


Additionally, the benefits of strength training may extend beyond improvements in actual performance as strength training in endurance athletes has been shown to have the potential to prevent overuse injuries (1). This may be due to strength training increasing the resiliency of your muscles, ligaments, and tendons through an increase in their overall strength as well as a correction of muscle imbalances across joints. The stronger your muscles are and the more balance that strength is across all of your joints, the better able you are to handle the repetitive stress of endurance sport.


A properly performed and technically sound strength training program has many benefits for endurance athletes. Next week, part II of this series will dive deeper into the practical recommendations for endurance athletes when it comes to designing and implementing a strength training program.



  1. Baechle, T. R. and Earle, R. W. (Eds.). (2008). Essentials of Strength Training and Conditioning 3rd Edition. Human kinetics.

  2. Bazyler, C. D., Abbott, H. A., Bellon, C. R., Taber, C. B., & Stone, M. H. (2015). Strength training for endurance athletes: theory to practice. Strength & Conditioning Journal, 37(2), 1-12.

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