Sports Watches – Heart Rate

Cardiovascular health benefits have been reported with doing any form of physical activity, so much so that exercise has been considered a form of medicine :).

Training responses in athletes are related to the training stimuli (such as training load) during the different cycles of training, dependent on where in your training year you are. Too much and too little training load can lead to either accumulated fatigue (overreaching or overtraining) or detraining respectively, thus making it important to have a balance that allows for optimal improvements in fitness and performance.

There are two indicators for quantifying the training load, these are: external, such as distance, power output, repetitions; and internal, such as oxygen uptake (VO2max), heart rate (HR), blood lactate, rate of perceived exertion (RPE). It is important to monitor these to ensure that the training you are doing is going to be beneficial rather than detrimental to your overall fitness and performance.

Heart rate is one of the measures that is non-invasive, relatively inexpensive (if your watch came with a HR strap or built-in wrist based HR monitor), and is quite time-efficient; and now with the watches one can monitor HR at any time.

So what am I looking for with my HR? Well firstly, one indication of a fit individual is how low the resting HR is. If you’re hovering around 50 bt.min-1, you’re looking good :). Additionally, we want to know what the upper-limit/your maximal HR is. The easiest way to determine this is through a calculation (not advanced): HRmax = 220 – age(in yrs). Furthermore, we are also wanting to understand how quickly your heart rate returns back/close to your resting HR following a bout of exercise (The faster, the better).

It has been shown, that it only takes about a week, in order to show improvements in post-exercise recovery HR following the start of an endurance program (1).

When is the best time to get the Resting HR values? These values are best recorded first thing in the morning (5-10mins upon awakening), or while lying down. When fitter, as previously mentioned, your resting HR will be lower. This then has implications for your exercising HR – it will also be lower, the fitter you are.

Your HR has a direct correlation to your O2 uptake, during continuous exercise. Correlations have been noted between decreases in HRex and improvements in high-intensity exercise performance. Although your HR can tell you a few things, it should not be used as the primary marker of fatigue and/or fitness impairment. Why? (you may ask) It is because HR is influenced by factors such as motivation/emotional state, temperature/environmental conditions, and/or sickness, among others. Recent data has shown that a >4% increase in HRex in response to an increased training load the day before a training session/camp, can be a good predictor for the athlete becoming sick within the next day (2).

Post exercise HR recovery reflects your body’s ability to adjust to its position, blood pressure, and how quickly you can essentially recover from your training session/race. It has been suggested that HR recovery is a relevant training monitoring tool in order to track positive changes in high-intensity performance (3).

Heart Rate recovery does fluctuate according to your training load periodization. When we look at the Autonomic Nervous System (ANS) activity over consecutive training blocks, moderate training loads are generally associated with slower HR recovery (4).  It is apparent that in endurance athletes, the cardiac autonomic regulation likely improves during the first part of the training phase (initial building or extensive endurance phase, likely leading to functional overreaching), while it decreases over the weeks preceding competition (tapering) (5).


So to summarize, for now:

Change in HR When does this occur? Mechanism What does it imply?
↓ Resting HR Short-term training program in moderately trained athletes or during build-up phase of elite athletes (high volume, low intensity) ↑ overall parasympathetic activity Coping well with training
↑ Resting HR Beginning of training block ↑ sympathetic activity
  1. If during short training blocks = ↑ readiness to perform
  2. If not = accumulated fatigue
↑  Resting HR During Tapering ↑  sympathetic activity
  1. If during tapering = ↑ readiness to perform
  2. If not = accumulated fatigue
↓ Resting HR Elite athletes or those with long training history ↑ parasympathetic activity
  1. Elite athlete/long training history = coping well with training, likely high-volume and low-intensity training
  2. If prolonged + not reversed with tapering, can indicate overtraining state
↓  Exercising HR Frequent in relation to changes in training load ↓  in relative ex. Intensity Cardiorespiratory fitness improvements
↑ Exercising HR Frequent in relation to changes in training load Likely ↑ in relative ex. Intensity Unclear, does not necessarily indicate ↓  performance capacity
↑  Post-exercise HR Very frequent, following short-term program in moderately trained athletes, and/or during the building up phase of elite athletes (high volume, low intensity) ↑  in overall parasympathetic activity
  1. If after short training program = ↑  readiness to perform
  2. If prolonged + not reverse with tapering, can indicate overtraining state
↓ Post-exercise HR Frequent during tapering ↑ sympathetic activity
  1. If during tapering after overload period = ↑ readiness to perform
  2. If not = accumulated fatigue

* Sympathetic activity: part of the autonomic nervous system that is associated with the fight or flight response. It is associated with an increase/acceleration of HR, constriction of blood vessels, and increased blood pressure

* Parasympathetic activity: part of the autonomic nervous system along with the sympathetic nervous system. It results in slowing the HR, increasing intestinal and glandular activity, and relax the sphincter muscles

The above table indicates how one can use the HR to determine not only your readiness/training adaptation, but also your possible state of fatigue and/or overtraining. (*The concept of overtraining and recovery will be covered at a later stage).

So this information is all well and good, but I’m sure you’re now thinking: “what about the HR zones?” or “why are there those colourful zones associated with the HR on my watch?”


The general HR zones are as follows:

Zone 1: 60-70% HRmax This zone should include long, continuous aerobic workouts at a low intensity where distance is the goal. This will allow you to build and maintain her aerobic endurance.
Zone 2: 70-80% HRmax This zone should include tempo workouts, where you would train at race pace, with the intention on building intensive endurance.
Zone 3: 80-90% HRmax This zone should include interval work, alternating high-intensity exercise periods with low-intensity recovery periods. These recovery periods would be active recovery, and not passive.


If you’re looking for more HR zones these are guidelines:


  Rating of Perceived Exhaustion (RPE) Ex. Time to exhaustion
Zone 1:

60-75% HRmax

Very light >3 hrs
Zone 2:

75-84% HRmax

Light 1-3 hrs
Zone 3:

84-89% HRmax

Some-what Hard 20 min – 1 hr
Zone 4:

89-93% HRmax

Hard 12 – 30 min
Zone 5:

94-100% HRmax

Very Hard 5 – 8min
Zone 6:

100% HRmax

Very Very Hard 1.5 – 2min

*Note: If you’re looking to identify your true HRmax, it is advised that you go for a maximal test, during which you can identify your anaerobic threshold, and use that to help tailor your HR zones accordingly, to assist in pushing your lactate threshold further. This maximal test is a VO2max test.

These HR zones are there to tell you when you are working in which zone, if you are doing more long distance/endurance training, you should be aiming for a HR zone between 60 and 70% of maximum, but if you’re doing high-intensity or sprint training, you should aim for a HR above 80% of your maximum – ideally, combine the two tables above. Additionally, if you do multiple sports, and not just run, the training HR zones may vary slightly.



  1. Buchheit, M., Chivot, A., Parouty, J., Mercier, D., Al Haddad, H., Laursen, P.B., et al.(2010a). Monitoring endurance running performance using cardiac parasympathetic function. Eur. J. Appl. Physiol. 108, 1153–1167.doi: 10.1007/s00421-009-1317-x
  2. Buchheit, M., Simpson, B.M., Schmidt, W., Aughey, R.J., Soria, R., Hunt, R., et al. (2013c). Predicting sickness during a 2-week soccer camp at 3600m(ISA3600). Br. J. Sports Med. i124–i127. doi:10.1136/bjsports-2013-09275
  3. Buchheit, M., Simpson, M.B., Al Haddad, H., Bourdon, P.C., and Mendez Villanueva, A. (2012). Monitoring changes in physical performance with heart rate measures in young soccer players. Eur. J. Appl. Physiol. 112, 711–723.doi: 10.1007/s00421-011-2014-0
  4. Borresen, J., and Lambert, M.I. (2007). Changes in heart rate recovery in response to acute changes in training load. Eur. J. Appl. Physiol. 101, 503–511. doi: 10.1007/s00421-007-0516-6
  5. Hug, B., Heyer, L., Naef, N. , Buchheit, M., Werhrlin, J.P., and Millet, G.P. (2014). Tapering for marathon and cardiac autonomic function. Int. J. Sports Med. (in press).

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