Does maximum heart rate influence performance?
Short answer, no. Cardiac output matters.
Your maximum heart rate has a higher chance of DECREASING as you get fitter. I’ll explain why.
Absolute numbers mean nothing, and relative numbers mean everything.
First, a recap of some important terms and science:
Heart rate (bpm). The number of heartbeats per minute.
Stroke Volume (Liters). The volume of blood pumped out of the heart per beat.
Cardiac output (L/min). The volume of blood pumped out of the heart per minute.
CO = HR x SV
The term “heart rate” describes the frequency (in beats per minute, BPM) at which the heart is beating at a given point in time. Combined with the stroke volume (the amount of blood ejected from the heart per beat, SV), we get the total quantity of blood being pumped from the heart to circulate around the body per minute (the cardiac output, CO). Blood carries oxygen and fuel to the muscles and removes carbon dioxide as a waste product. At rest, our need for this process is low, so the heart can beat relatively slowly to fulfill requirements. However, during exercise, the demand for blood increases dramatically, and, as the ability for stroke volume to increase is low, this is primarily met by increasing heart rate, making heart rate a good indicator of how hard the body is working to produce metabolic power. Consequently, heart rate has been used by athletes and coaches for several decades to objectively measure exercise intensity and prescribe training.
Through the development of wrist-based HR sensors, many runners have started utilising heart rate in their training, which has led to some dubious ‘experts’ touting bro-science about HR and fitness. Despite heart rates’ advantages over earlier training metrics, such as perceived exertion, heart rate is not a perfect training tool.
One number I see thrown around is maximum heart rate (HRmax). The higher your heart rate the better runner you are or, the better you are at pushing yourself. These statements are simply WRONG.
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HRmax Changes with Training
Some of the proposed mechanisms for changes in HRmax that may occur with aerobic training include autonomic (extrinsic) factors such as plasma volume expansion and enhanced baroreflex function, while some non-autonomic (intrinsic) factors are alteration of the electrophysiology of the sinoatrial (SA) node and decreased ß-adrenergic receptor number and density. (REF)
(Zavorsky, G.S.2012 researched changes in HRmax with aerobic training and revealed that HRmax can be altered by 3 to 7% with aerobic training/detraining. That’s increasing with detraining, and decreasing with training.
Yet, Zavorsky concluded;
“However, because of a lack of research in the area of training on HRmax, the reader should remain speculative and allow for cautious interpretation until further, more thorough investigations are carried out as to the confirmation of the mechanisms involved.”
High & Low Heart Rates Compared
Introducing Lionel “The Colonel” Sanders. World-class long-distance triathlete.
HRmax = 165bpm
How can a professional athlete with an FTP of over 400W and 5km PR of < 15min have a HRmax of 165bpm?
Cardiac output (CO).
Remember, CO refers to the amount of blood being pumped per beat of the heart. Cardiac output is affected by stroke volume (SV) and heart rate (HR). Just because your heart rate is low doesn’t always mean you’re not pumping as much blood (and oxygen) compared to if your heart rate was high.
The oxygen cost (VO2) of running 5min/mile (3min/km) or riding 400W is pretty much the same across athletes due to economy, so it’s not that Lionel, or anyone with an abnormally low HR, requires less O2, it’s that they have a large stroke volume per beat, so they don’t need as many beats to get the same amount of blood pumped around their body, i.e. cardiac output.
Me Vs Lionel
Cardiac Output = Heart Rate x Stroke Volume
CO = HR x SV
Lionel
CO = 165bpm x 4 L
CO = 660 L/min
Dr Will
CO = 202bpm x 3 L
CO = 606 L/min
How can I use this information to help me?
Always use relative (%) heart rate measures.
If Lionel and I run at 80% of our HRmax. He’ll be running at 132bpm, and I’ll be running at 162bpm, but we’ll running at the same intensity because we’re using a number relative to OUR max, not someone else’s. If Lionel ran at my 80% (162bpm), he’d be smashing it, likewise, if I ran at Lionel’s 80%, I’d be jogging.
Next time you’re comparing your runs on Strava have a look at the other runners’ “time in zones” rather than their absolute heart rate (or pace) numbers.
Happy Running!
Dr Will
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