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Demystifying the Science Behind Performance

Do the words VO2 Max, lactate threshold, and neuromuscular adaptations leave you feeling like you’re in a foreign country, trying to speak a new language? That’s quite alright—the exercise research world is an expansive place with too much confusing jargon to keep track of… and many athletes (and coaches) misuse these fancy science words anyway! The goal of this article is to demystify these terms and help you to understand the ones that are important for success in training and racing.

The goal of most triathletes is to get faster… but how exactly does “getting faster” happen? Generally, improving performance means that your body is making changes (“physiological adaptations”) so that efforts that used to feel difficult become easier. Essentially, each time you train, your body reacts by rebuilding itself to be a little better at that specific task that you asked it to perform. As a result, training should make any given effort, or pace, feel easier. One concept to understand, that helps to tie together the components of training and performance, is fatigue. We generally slow down or stop due to fatigue, and the below figure captures what makes one “fatigued” (Enoka and Duchateau, 2016). Improving VO2 max, lactate threshold, and economy all allow us to go faster with less fatigue.

How do we improve these things?                                                                                               

There are components of physiological function that can be tested, and can help to predict performance. Which are the most important to consider? Well, three of the heavy hitters are: lactate threshold, VO2 max, and economy. These may all be improved with certain types of workouts. The goal of this article is to help you understand what each physiological parameter means, how they may be measured, and how to improve them!

Lactate Threshold (LT): This is technically defined as the exercise intensity at which lactic acid accumulates at an exponential rate (think - a switch from a slow, constant accumulation to rapid accumulation at a quicker and quicker rate). Lactate threshold is often associated with the power output during a “FTP” cycling test (Functional Threshold Power) or a “Critical Power 60” test in cycling. These field tests are not an accurate estimation of your lactate threshold; however they do provide useful pacing guidelines. Your lactate threshold tells you at what intensity that you can work where the factor limiting your performance is not your cardiovascular system. If you do not have access to laboratory testing, lactate threshold fairly consistently occurs at 75-80% maximal heart rate. So to estimate your own lactate threshold, simply try to nail down the pace (in swimming, biking or running) where you can stay within that 75-80% maximal heart rate. Improvements in LT are associated with improvements in 40K cycling TT performance, 3K running performance, and most other endurance events.

How do you improve your LT? Contrary to popular belief, training right at your lactate threshold pace is not the best way to improve your LT! The fastest way to improve lactate threshold is through short, high-intensity intervals performed at intensities above the lactate threshold (Neil et al., 2013; Seiler et al., 2013).  Workouts like 4 x 4 minutes or 4 x 8 minutes of maintaining your best average power or pace have been found to improve lactate threshold (as compared with doing longer intervals, like 4 x 12 or 4 x 16 minutes). Another traditional workout that improves LT is a longer “Tempo Run” or ride. These target 20-60 minutes of effort at or near LT, and can also be referred to as working at “Threshold Pace.” These types of workouts may not create as robust of an improvement in LT, but they do develop specific muscular endurance that is still critical for races over 1 hour.   

VO2 Max: This is quite a buzzword in the endurance sport and coaching world. To start out, let’s break down the term into its two parts. “VO2” refers to the amount (Volume) of oxygen (O2) your muscles can take-up (or “consume”) and convert into carbon dioxide. And, as you likely guessed, the “Max” portion of this term refers to it being “maximal.” It might help to think of VO2 Max as “maximal oxygen utilization,” or the point at which no matter how much oxygen you are breathing in, your body simply cannot use any more for exercise than it is already. Translating this to performance, a lower VO2 Max can really limit your top-end endurance capabilities, as the ability for your muscles to consume more oxygen would obviously allow them to work harder. This maximal ability to deliver and use oxygen is directly related to your performance in longer races. Laboratory testing is the only way to accurately determine VO2 max, but for training and racing purposes, it is not actually a critical value to measure! Simply knowing that you are improving it is enough. However, if you are curious, there are a few conversion tables to estimate your VO2 Max value based on your best cycling or running times (like http://sdtrackmag.com/DanielsOneSheet.pdf, developed by legendary exercise physiologist and running coach, Jack Daniels).

How do you improve your VO2 Max? Individuals just beginning to train will improve their VO2 max simply by increasing their training volume, but a more experienced athlete requires specific training. Short (1-4 minute) intervals where you really get out of your comfort zone (90-100% maximal heart rate) are the fastest way to improve your VO2 max. In these efforts, at least an equal amount of recovery time is often required between bouts, sometimes even a longer recovery than the length of the hard bout. An example workout: 10 x 60 seconds running nearly all out (90=95% effort) with 60 seconds – 90 seconds recovery between. Recovery can either be “active” yet easy (slow jog) or “complete recovery” (standing or walking).

Neuromuscular Efficiency: This term is often used by coaches as it pertains to the benefits of your fastest work, like strides, speed work under 30 seconds in length, plyometrics or lifting at a moderate to high speed. Technically, neuromuscular efficiency is measured as the “metabolic cost” of running, riding, or swimming at a given intensity (with metabolic cost referring to the amount of oxygen, VO2, that is consumed to do that activity at that intensity). ‘Neuromuscular’ refers to the junction where your nervous system sends commands (in the form of electrical current) to the muscles. Practicing these short but powerful movements has an interesting and slightly unexpected effect: it dramatically increases your efficiency in events where you are sustaining much slower paces, such as marathon, 10K, or 5K. To summarize what adaptations are happening at this neuromuscular junction to increase efficiency, let’s look a little closer at the anatomy of the human body! Your muscles consist of many “fibers” bundled together (think – hundreds of pieces of rope in a parallel bundle, but some pieces of rope are thin and only consist of a few strands of material twisted together, while other are massive and contain many twisted, entwined strands). Your nervous system is designed to only recruit the particular muscle fibers required for a task (small ropes for “easy” tasks, large ropes for “heavy” tasks). If you only perform low intensity contractions, you only use the few muscle fibers required. As you get into a maximal lift or sprint, you now recruit all of the fibers within a muscle, “enhancing” the connection between your neural and muscular systems, and allowing your body to more easily recruit new muscle fibers when needed, for example at the end of a race when you try to sprint it in to the finish!

How do you improve efficiency? Weight lifting, plyometrics, and short, high intensity efforts (10-20 seconds) dramatically improve efficiency at easier intensities or paces. This is probably the most often neglected component of triathlon training! For anyone who is looking to improve performance without sacrificing too much time, this provides some low hanging fruit and great bang-for-your-buck! Even a single bout of weight training has been shown to increase muscular performance one week afterward, suggesting a quick and robust neuromuscular adaptation (Kamen and Knight, 2004).

The takeaway: While shorter, high intensity intervals are the fastest way to improve VO2 Max, Lactate Threshold, and running efficiency, many athletes need to begin by building a base level of fitness, which comes from consistent training volume in their respective sport. None of these higher-intensity training sessions should be incorporated until you develop a strong base, with the exception of weight training, which may aid in injury prevention (when done correctly). Work with a coach to periodize your training plan so that each week contains mostly easy days, a few specific hard days, and a few long, endurance-focused days. Each year should also contain raining cycles that emphasize different areas for improvement. The human body works best by adapting to new stimuli, so stop doing the same old routine and mix it up!

Written by: Dan Feeney, M.S. in Biomechanics and Melissa Mazzo, B.S. Exercise Physiology (both from the University of Delaware).  Dan is a PhD candidate in neurophysiology at the University of Colorado and Melissa is about to complete her masters in Integrative Physiology. Both Dan and Melissa are avid triathletes and runners. They recently launched a coaching business to share their knowledge of sport and science… Velocity Canyon Endurance Project: www.velocitycanyonenduranceproject.com

@ VCenduranceproject on Instagram


1) Enoka RME, Duchateau J. Translating fatigue to human performance. Med Sci Sports Ex. 11: 2228-2238.

2) Kamen G, and Knight CA. Training-related adaptations in motor unit discharge rate in young and older adults. Journals Gerontol 59: 1334–1338, 2004.

3) Neil CM, Hunter AM, Brennan L, O'Sullivan A, Hamilton DL, De Vito G, Galloway SD. Six weeks of a polarized training-intensity distribution leads to greater physiological and performance adaptations than a threshold model in trained cyclists. J Appl Physiol, 114: 461-471, 2013

4) Poole DC, Burnley M, Vanhatalo A, Rossiter HB, Jones AM. Critical Power: An Important Fatigue Threshold in Exercise Physiology. Med Sci Sports Ex., 48: 2320-2334, 2016.

5) Seiler S, Jøranson K, Olesen BV, Hetlelid KJ. Adaptions to Aerobic interval training: interactive effects of exercise intensity and total work duration. Scand J Med Sci Sports 23: 74-83, 2013

AJ Baucco Coaching is world class triathlon coaching for age group athletes of all ability levels. We specialize in Full Service Triathlon Coaching, but we also create Focused Training Plans for athletes that like a more hands off approach. Feel free to contact us with any questions or to set up an informational phone call.

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