Build training zones around effort, not age
High confidence
Good training zones are built around your effort thresholds, the points where your breathing deepens and the burn in your legs steps up. Those thresholds fit you better than zones set from a maximum heart rate that was only guessed from your age.
Why it works
Two effort thresholds mark where your body shifts gears: the ventilatory threshold (where breathing jumps) and the lactate threshold (where the burn sets in). At those points, your body changes how it burns fuel and how it clears acid. Train just below, at, or above a threshold, and your body gets used to a different demand each time.
The evidence
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This is a joint expert and consensus statement, not an experiment. A panel from the American College of Sports Medicine and Exercise and Sport Science Australia noted that inconsistent intensity labels across studies and guidelines hold back research and make exercise advice harder to follow. To fix that, they propose one shared scale of 5 intensity levels: very low, low, moderate, high, and very high. The paper defines each level so researchers, clinicians, and coaches can describe exercise intensity the same way.
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In controlled studies, threshold-based prescription raised VO2max more than traditional percentage-based prescription (4.1 vs 1.8 mL/kg/min), and 64% of people in threshold groups improved by more than one MET compared with 16% in traditional groups. Non-controlled studies showed the same direction (4.4 vs 3.4 mL/kg/min). Spread of individual responses did not differ between the two approaches.
n=1544
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Reviewing descriptive studies of nationally and internationally competitive endurance athletes training 10 to 13 times per week, Seiler found their intensity distribution converges on roughly 80% of sessions at low intensity (around 2 mM blood lactate or below) and about 20% dominated by high-intensity work such as intervals near 90% VO2max. Training-intensification studies in already well-trained athletes gave no convincing evidence that more emphasis on high-intensity interval training brings long-term performance gains. The review suggests that mostly low-intensity, long-duration training combined with fewer, highly intensive bouts may be complementary for adaptive signaling and technical mastery at an acceptable level of stress.
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Using measured maximal heart rate from 3,320 healthy adults across a wide age range (the HUNT Fitness Study), the authors found that three previously used prediction formulas underestimated true max heart rate in people older than 30. They proposed a better fit: max heart rate equals 211 minus 0.64 times age. The relationship showed no interaction with sex, physical activity level, fitness (VO2max), or body-mass index, though individual results still varied by about 11 bpm (standard error 10.8 bpm) around the prediction.
n=3320
Why we call confidence high
A 2025 meta-analysis of individual data from 1,544 people in 42 studies (Meyler et al.) found that training set from physiological thresholds raised VO2 max more than training set as a percentage of maximum heart rate, heart rate reserve or VO2 max (4.1 vs 1.8 mL/kg/min in controlled studies), and 64 percent of people improved meaningfully versus 16 percent. Age-predicted maximum heart rate also carries a standard error of about 11 beats per minute (Nes 2013). Seiler 2010 describes how endurance athletes spread training across threshold-anchored zones, and Bishop 2025 proposes a common five-level intensity scale. In one small clinical sample, a formula target (35% of heart rate reserve) matched the first ventilatory threshold closely (Liu 2025), so formula zones are not always far off. The head-to-head evidence comes mostly from untrained and recreationally active adults rather than trained runners.
Where it applies
Healthy adults, including recreational and trained runners. The direct comparison of threshold-based and percentage-based prescription comes mostly from previously untrained or recreationally active adults; the evidence in trained runners is descriptive.
Last reviewed Oct 14, 2026. See how we score.