PT on the Net Research

How Fast Can the Heart Beat?


Question:

I have a client who's heart rate shot up while undertaking the three minus point aerobic test on the treadmill. She runs regularly on the treadmill, but during the test, at the third workload minus, she was running at a speed of 10.9 km/h minus her heart rate shot up to 225 bpm. I slowed her down to walking immediately as it was obviously too intense for her, and her heart rate recovered and stabilized very quickly. Because of the basic formula to calculate max HR as 220 minus age, I have it in my mind that 220 is the maximum beats per min that a heart can beat. I know that this can't be true, so could you please advise me on how fast the heart can beat and any other information that you feel would be useful with regards to the above?

Answer:

Based on gender averages, women have a lower blood volume and smaller hearts (therefore, smaller left ventricles) than men. Cardiac Output for the same absolute output is however generally the same in both sexes. With heart rate and stroke volume being the predominant determinants of Cardiac Output, the virtual equality would mean that an increased heart rate in females is needed to compensate their smaller stroke volumes.

Considering this, Shield and Young recommended the use of the following formula modifications:

PMHR  =  220 minus Age (Males) and 225 minus Age (Females)

However, with this in mind, current research has maximal heart rate being genetically determined, and although influenced by age, it is not determined by gender or fitness.

Back to maximal heart rates. The formula 220 minus age is actually used to determine the Predicted Maximal Heart Rate (predicted being the key word). In fact, several other formulas for predicting maximal heart rate have alternate "maximal" start points including:

Dr. Haskell, one of the proposers of the 220 minus age formula in the 1970s, stated that the formula was never meant to be used as an absolute guide to govern training. With this in mind, the formula is a rough guide providing some standardization and a basic start point for developing training intensities, but it is not the absolute formula.

Highlighting this fact, Dr Lauer. found that, during studies looking at heart rate recovery times as a predictor of heart disease, more than 40 percent of patients would break the age predicted maximum based on the 220 minus age formula. Furthermore, studies by Tanaka & Seals et al in 2001 found that the formula underestimates maximal heart rates in older adults, leading to the recommended formula change to 208 minus 0.7 (age).

Having looked at gender and the formula itself, one other often neglected area must be addressed, that being how the heart rate was measured. While monitors using heart straps are considered more accurate, accuracy can be affected if not positioned correctly or the strap is not sufficiently lubricated. Likewise, grip monitors (e.g., on handlebars) are influenced by skin conditions (temperature, vasodilation, etc) as well as the conduction between hand and monitor.

Personally, the methods I use for monitoring a change in my client’s fitness are:

  1. The Karvoenen formula ({[PMHR – Resting Heart Rate] X Intensity} + Resting Heart rate) to determine training intensities at 60, 70 and 80 percent measuring actual heart rates, their own rate of perceived exertion (RPE) (this lets me know if I can or cannot increase the workload) distance covered and speed. I then repeat the test in several weeks and plot the differences (Microsoft Excel does this well) by either getting them to repeat the same speeds and use their HR and RPE as outcome objectives or use the same PHMR (not readjusting their Heart Rate Reserve for their Karvoenen formula) and using their Speeds, Distance and RPE as outcome objectives. The benefit of this method is that it provides both objective and subjective outcomes.
  2. If a patient does desire to compare herself to the "normative" population, I prefer to use a VO2 test, either in a lab or using the 20 m Progressive Shuttle Run ("Beep") test and comparing her results to obtained data. 

I hope this helps.

References:

  1. Fox SM, Haskell WL: The exercise stress test: needs for standardization, in Eliakim M, Neufeld HN (eds): Cardiology: Current Topics and Progress. New York, Academic Press, 1970, pp 149-154
  2. Jones,K., & Baker,K.,(1996). Human Movement Explained.  Jordin Hill,Oxford : Butterworth & Heinemann.
  3. Kolata, G (2001) 'Maximum' Heart Rate Theory Is Challenged, The New York Times’ Published: April 24, 2001
  4. Londeree and Moeschberger (1982) 'Effect of age and other factors on HR max' - Research Quarterly for Exercise & Sport, 53(4), 297-304
  5. Miller et al (1993) - 'Predicting max HR' - Medicine & Science in Sports & Exercise, 25(9), 1077-1081
  6. Shield,T., & Young, L.(1995). Fitness a Systematic Approach. Coorparoo, Bne: Fitlink.
  7. Tanaka H, Monahan KD, Seals DR: Age minus predicted maximal heart rate revisited. J Am Coll Cardiol 2001;37(1)153 -156