Monitoring Adaptations Using HR Responses to Submaximal Exercise

Martin Buchheit of Aspetar, Tzlil Shushan of the University of Wollongong and Shaun McLaren of Newcastle Red Bulls show team-sport performance staff how to run a 3–4 minute submaximal run, read the heart rate response and tell a fitness change from heat, plasma volume or fatigue.

About this webinar

Martin Buchheit, high performance lead at Aspetar, leads the session with Tzlil Shushan, sports scientist and lecturer at the University of Wollongong, and Shaun McLaren, consultant sports scientist and strength and conditioning coach at Newcastle Red Bulls. They draw on their recently published paper summarizing 20 years of research on heart rate responses to submaximal exercise, with data from football, rugby union and Australian football. They cover protocols, speed, analysis, how a change relates to maximal aerobic speed (MAS) and what else moves heart rate. This is part one of two. The session runs about one hour and was recorded on 30 Oct 2025.

What you will learn

• Why the panel tracks exercise heart rate only, and drops heart rate variability and heart rate recovery as too noisy
• How to set a shuttle at 11.8 km/h so each 50 m takes exactly 16 seconds
• Why the mean of the last 30 or 60 seconds is the number to keep, and why 3 minutes works almost as well as 4
• How a 2.5–5.5 percentage point drop in submaximal heart rate relates to a 0.5 km/h gain in MAS
• Why heart rate rises by about 1 percentage point for every 10 °C, and how to correct for it

Practical examples from the recording

1. The figure-of-eight on a football pitch. Buchheit runs players in a figure of eight around the pitch. Each leg is 50 m, so covering it in 15 seconds puts the player at 12 km/h, with cones for pacing. The pitch dimensions give him the 50 m legs in a few steps, without marking. He runs it early in the session because, for footballers, the intensity is low. McLaren notes that it feels less like a test than a shuttle.

2. A shuttle for a 55-player rugby squad. McLaren has up to 55 players on a 100 by 70 m pitch, so he uses a 50 m shuttle from try line to halfway, six times there and back, for a 3-minute run. Each change of direction costs about 0.7 seconds. Rather than timing 15.3 seconds for 12 km/h, he runs at 11.8 km/h: exactly 16 seconds per 50 m, with cones every 25 m. The panel’s view is that the exact speed matters less than keeping it the same every time, with heart rate landing between 70% and 90% of HRmax.

3. Reading a change against MAS. Across cohorts and protocols, a 2.5–5.5 percentage point drop in a player’s submaximal heart rate went with about a 0.5 km/h gain in MAS, one level on the 30-15 Intermittent Fitness Test. McLaren works with about 4 points on average, or 5 to be conservative. The correlations sit around 0.6–0.7, and in Buchheit’s Aspire data, heart rate changes did not track countermovement jump or 10 m times, so the test speaks to aerobic fitness only.

4. Correcting for heat and plasma volume. Buchheit’s pilot data from Paris Saint-Germain, and Shushan’s 2025 data from senior football players in Australia, both show heart rate rising by about 1 percentage point for every 10 °C. On a hotter day than usual, take a few points off; on a colder one, add them. Heat training can also expand plasma volume by 5–7% and lower submaximal heart rate. Buchheit counts that as real but partly transient, so large drops after heat exposure deserve caution.

Questions answered in the Q&A

Are there normative submaximal heart rate ranges by sport? No, it is individual. Test weekly and each player has a personal range in about 10 weeks. Until then, McLaren’s rule of thumb is that 70% of HRmax probably means fit and 90% probably means unfit.

How often should you run a submaximal fitness test? At least once a week or every two weeks, according to the panel, and more often if you can. Buchheit adds that rest and high-intensity days matter for timing because of plasma volume, a topic for part two.

Where does the test fit in the session? In the warm-up. McLaren’s rugby players do five minutes of general preparation, then the 3-minute run, then move on to agility or high-speed running. Shushan adds that a short warm-up first also improves sensor connectivity.

Should the test speed be set from critical speed or the first lactate threshold? Physiologically, around the first lactate threshold rather than critical speed. In practice, McLaren says team-sport players will sit somewhere around 10–13 km/h, and the speed only needs to bring heart rate between 70% and 90% of HRmax.

Can a lower heart rate mean fatigue rather than fitness? Yes. In a case study of functional overreaching, submaximal heart rate fell while perceived effort rose to 20 out of 20 from 18. McLaren’s tell-tale sign: lower heart rate with higher RPE points to fatigue, while lower heart rate with lower RPE after a solid training block points to fitness.

Who this webinar is for

Heads of performance, sports scientists and strength and conditioning coaches in professional football, rugby and other team sports who need an in-season aerobic fitness check without a maximal test, and return-to-play staff who cannot test maximally in rehab.