This month we will focus on one facet that keeps multisport interesting—at times puzzling—that is the difference in heart rates (HRs) between the events. How do you shift your training HRs from running for the bike and swim? This was a groundbreaking research topic in the late 1980s, beginning with Dr. Mary O’Toole’s assessment of 1984 Hawaii Ironman participants (during the semester that Dan had Dr. O’Toole for cardiovascular exercise physiology class). 

Pinpointing the HR and lactate threshold differences between events is analogous to predicting your HR max from a prediction equation, such as 220 minus age, or the newer and more accurate 208 minus (0.7 x age)— these have large standard deviations. However, while genetics largely determine your HR max for your best event, it is usually your training background and degree of technical skill in your “lesser” events that determine how the HR max and lactate threshold HR will compare to that of your best event.

Dr. O’Toole studied 8 men (VO₂ 68.8 +10 treadmill, 66.7 + 10 bike, age 30) and 6 women (VO₂ 65.9 + 8 treadmill, 61.6 + 7 bike, age 31) and found that the men averaged only 3 beats per minute lower on the bike than treadmill (178 + 8, 181 + 6) while the women averaged 8 bpm lower on the bike than treadmill (179 + 8, 187 + 8).  The small sample sizes of such studies make it difficult for differences to achieve statistical significance, as was the case here.

The same year, in 13 male recreational triathletes (VO₂ 60.5 treadmill, 57.9 bike, 52 swim, age 29) Wendy Kohrt found the bike HR only 2 bpm below treadmill, with the swim a significant 14 bpm lower (192 + 7 treadmill, 190 + 7 bike, 178 + 10). 

In 1988, in 9 males age 28, Richard Kreider found bike HRs were 8 bpm lower than treadmill and oddly, 2 bpm lower than swimming (194 + 8, 184 + 8, 188 + 7 swim).  These non-significant differences did not match the VO₂ data of 68 +12 Treadmill, 64 + 9 bike and 51 + 8 swim.  Also of interest, the bike LT was 11 bpm lower than the treadmill LT. 

To satisfy your curiosity, at age 30 Jeff’s HR max was 211 for both running and cycling.

Back when he was a runner who was new to cycling, he was 7-8 bpm lower on the bike. 

So what sense can we make of all these differences in data?  Bottom line—there is a ton of variability between people!  In his coaching, Jeff subtracts 10-15 beats from the running LT to estimate the cycling LT for runners who are new to cycling.  Conversely, for a cyclist who is just starting to run, he assumes that the LT for running and cycling are approximately the same.  Dan assumes that for most runners who start triathlon training, the HR max for running will be approximately 6 bpm higher than for cycling and 10-12 bpm higher than for swimming.  For those purists who want to know for certain, Dan tests some athletes on the treadmill one year and bike the next year.  Oh, the interesting challenges of multisport—they keep you coming back for more…

References:

1. Kohrt, WM, et al., Physiological responses of triathletes to maximal swimming, cycling, and running. Medicine & Science in Sport and Exercise. 19(1):51-55, 1987.
2. Kreider, RB, et al., Cardiovascular and thermal responses of triathlon performance. Medicine & Science in Sport and Exercise. 20(4):385-390, 1988.
3. O’Toole, ML, The ultraendurance triathlete: a physiological profile.  Medicine & Science in Sport and Exercise. 19(1):45-50, 1987.