Minimum Effective Dose for Endurance Training

Although coaches spend most of their time trying to help athletes fit more training into their busy lifestyles, there are times when life gets in the way and other priorities eliminate or dramatically reduce available training time. There are also times, particularly at the end of a long season, when athletes need a break. These scenarios beg the questions: what’s the minimum effective dose for training, and how long can you preserve endurance performance at this level of training?

What is Minimum Effective Dose?

Generally, a “minimum effective dose” is the smallest amount of input required to elicit a desired outcome. As an athlete, your goal is to train more than the bare minimum required to preserve performance. However, investigating the minimum amount of exercise required to elicit a training response helps us to understand the dose-response relationship as athletes add more training volume, frequency, and intensity. It is also important because studies have shown that minimizing the decline in performance between seasons is associated with greater performance improvements during the next season (Mujika 1995, and Rønnestad 2014). As I’ve told athletes for many years, it is very difficult to make year-over-year improvements when you must spend four to six months just losing and regaining fitness.

A May 2021 review in the Journal of Strength and Conditioning Research by Speiring et al took a fresh look at the minimum effective dose of exercise. As we head into fall and winter and the impending Holiday Season that seems to stretch from October to January, you may find comfort knowing that – if you must – you can get away with significantly reduced training without losing much of your hard-earned fitness.

It all depends on how you reduce your training, what components of exercise you keep doing, and what aspects of endurance performance you’re trying to preserve. The review specifically defined short-term endurance as “time to exhaustion at workloads equal to ~100% of VO2 max, which generally lasted 4-8 minutes” and long-term endurance as “time to exhaustion at workloads equal to ~80% of VO2 max, which generally lasted 1-3 hours”.

Reducing Frequency

As with a lot of sports science research, it is important to consider the fitness level and training experience of the subjects. Researchers conduct more studies with untrained or moderately fit subjects than with trained athletes. For generally active people, reducing training frequency from 6 sessions per week to as few as two sessions per week (keeping session duration constant at 40 minutes/workout and intensity constant) for five weeks didn’t significantly reduce VO2 max (Hickson and Rosenkoetter 1981). However, newer studies (90’s and 2000s) with trained subjects–more relevant to the audience of this blog–indicate that reductions in training frequency should be kept to 20%-50% which is basically reducing frequency by one day per week (5 days to 3 or 4, for instance).

Reducing Volume

What about shorter rides? As a matter of practicality, I am always leery of removing training sessions from an athlete’s weekly schedule. Once athletes allocate that time to something else, it rarely comes back. So, even though you can reduce frequency and maintain performance, I’d rather keep the number of training days constant and change what you’re doing within those sessions.

If you’re riding six days a week (I’m using that example because it’s what the main studies referenced in Spiering’s used), what happens when you cut the duration of those sessions by 33% of 66%? In another experiment by Hickson, intensity and frequency were constant for a 15-week period. Short-term endurance (4- to8-minute efforts) was largely unaffected by either a 66% or 33% drop in per-session training duration. Subjects retained long-term endurance (80% of vo2 max for 1-3 hours) with the 33% reduction but not with the 66% reduction in per-session volume.

It should be noted that the initial workout durations in Hickson’s studies were only 40 minutes. The reduced-volume sessions were 26 and 13 minutes, respectively. The intensities were high (90-100% of maximum heart rate), too. As a result, the workout parameters don’t perfectly match endurance cycling workouts (which are typically longer at lower intensities). However, the Spiering review points out that research on tapering – which is similar but not the same as reduced training – indicates that training volume can be significantly reduced (60-90% over 4 weeks in the case of tapering) and preserve or even improve performance.

Reducing Intensity

Here’s where things get interesting. Reducing frequency and/or volume didn’t have much of a detrimental effect on endurance performance. Backing off on the intensity did. In a third study, Hickson held frequency at 6 workouts per week and held volume constant at 40 minutes per session but reduced intensity to either 82-87% of max heart rate or 61-67% of max heart rate. In this study, long-term endurance (1-3 hours) performance dropped in both groups. Short-term endurance (4-8 minutes) was only retained in the 82-87% group. This too, bears some similarity to tapering research, where the successful formula for preserving or improving performance is to reduce volume and training frequency but retain intensity. The difference here is that tapering is typically a 4-week period and the reduced training studies lasted 15 weeks.

The table below illustrates the various combinations mentioned above:

Final Answer?

This is sports science, so you know there’s no final answer. Each new study or review adds context and new information. The Spiering review reinforces the idea that exercise intensity is the key variable for maintaining endurance performance during a period of reduced training. It also seems clear that maintaining performance is easier than building fitness and improving performance. The minimum effective dose of training isn’t that much – two or three workouts, about 60 minutes each, that include some hard intervals. Do that and you’ll retain the vast majority of the adaptations you’ve already earned.

So, when the weather turns cold and cruddy, end-of-the-year reports and projects keep you at work late, and family trips to your long-lost uncle’s house steal away precious training time, don’t fret. Do what you can, as frequently as you can, and just make sure to include some intensity. You might be treading water, so to speak, instead of making forward progress. Nonetheless, you’ll set yourself up with a chance to exceed your performance level next season.

By Chris Carmichael,
Founder and Head Coach of CTS

References:

Spiering, Barry A.1; Mujika, Iñigo2,3; Sharp, Marilyn A.1; Foulis, Stephen A.1 Maintaining Physical Performance: The Minimal Dose of Exercise Needed to Preserve Endurance and Strength Over Time, Journal of Strength and Conditioning Research: May 2021 – Volume 35 – Issue 5 – p 1449-1458 doi: 10.1519/JSC.0000000000003964

Includes

• Hickson RC, Foster C, Pollock ML, Galassi TM, Rich S. Reduced training intensities and loss of aerobic power, endurance, and cardiac growth. J Appl Physiol (1985) 58: 492–499, 1985.
• Hickson RC, Kanakis C Jr, Davis JR, Moore AM, Rich S. Reduced training duration effects on aerobic power, endurance, and cardiac growth. J Appl Physiol Respir Environ Exerc Physiol 53: 225–229, 1982.
• Hickson RC, Rosenkoetter MA. Reduced training frequencies and maintenance of increased aerobic power. Med Sci Sports Exerc 13: 13–16, 1981.

Mujika I, Chatard JC, Busso T, et al. Effects of training on performance in competitive swimming. Can J Appl Physiol 20: 395–406, 1995.

Mujika I. The influence of training characteristics and tapering on the adaptation in highly trained individuals: A review. Int J Sports Med 19: 439–446, 1998.

Mujika I, Padilla S. Physiological and performance consequences of training cessation in athletes: Detraining. In: Rehabilitation Of Sports Injuries: Scientific Basis. Frontera WR, ed. Malden, MA: Blackwell Science, 2003. pp. 117–143.

Slettalokken G, Ronnestad BR. High-intensity interval training every second week maintains VO2max in soccer players during off-season. J Strength Cond Res 28: 1946–1951, 2014.