With the influx of technology into the fitness industry, trainers are now provided with better tools to monitor the progress of the clients. Heart rate monitors represent an easy-to-use, non-invasive means to assess one's internal response to training, and they provide useful information regarding specific adaptation to training programs. Heart rate monitors provide objective information regarding cardiac physiology, allow the trainer to monitor intensity and work to rest ratios, and provide feedback to ensure training targeting specific adaptations is properly administered. This article will provide a brief overview of the advantages of heart rate monitoring during endurance-based exercise methods.
Heart rate (HR) is the number of times the heart contracts per unit of time, usually expressed as beats per minute. The heart rate is regulated by the sinoatrial node, a group of cells located in the wall of the right atrium, and is innervated by fibers from the parasympathetic (vagus) and sympathetic (accelerans) nerve branches of the autonomic nervous system. Normal resting heart rate has been reported to be between 60 to 100 beat per minute, although it is typically lower in aerobic athletes.
Resting heart rate has been suggested to be a marker of training tolerance. Determinants of resting heart rate include cardiac muscle morphology, plasma volume, autonomic activity, age and body position. A reduced resting heart rate is an indication of the effect of improved cardiovascular fitness. However, an increased resting heart rate could indicate early stages of accumulated fatigue. Resting heart rate should ideally be measured directly when waking and tracked over time to monitor changes meaningful to the individual, although studies have measured resting heart rate during the final five minutes after 10-minutes of lying down. A progressive rise of 10 beats per minute above the lowest recorded level suggests that the training load may have exceeded the athlete's functional limits; however, this arbitrary value may not be representative of meaningful changes in resting heart rate. While an increase in resting heart rate is typically indicative of increased sympathetic tone at rest, depending on the stage of training, this increase might be a positive adaptation to training. Making inferences in the training status of an athlete using resting heart rate can often be misleading, but when used in conjunction with elements such as volume and intensity of training, can provide context.
Measuring a maximal heart rate ensures that the coach is able to accurately prescribe training based on an individual's physiological status and can be used to monitor training tolerance. Maximal heart rate is highly variable between individuals, with very little of the variability validated by age alone. Estimates of maximal heart rate using the age-based prediction formula (220-age) exhibit relatively large standard deviations (≥ 10 beats per minute) so age-based predictions should be used with caution. Clinical and field are effective in obtaining a max HR, which in most cases can be more accurate than simply using an Age-Predicted Max HR Formula such as 220-age or 208 - .70(age). However as with any testing protocol, caution should be exercised and screening standards should be followed. For maximal tests, all participants should have a fully documented health and medical history. Depending on that history, a full medical exam may be warranted. Depending on those results, the maximal test protocol may need to be medically supervised.
The tracking of heart rate recovery is another method for tracking training status and accumulated fatigue. Submaximal tests such as the Heart Rate Interval Monitoring System (HIMS) have been utilized in the research to monitor heart rate recovery. The HIMS test is a 13 minute submaximal fitness test, consisting on four, two minute stages of increasing intensity (8.4, 9.6, 10.8 and 12.0 km·hr-1, respectively) runs between two 20m lines. Heart rate is tracked during the test, as well as throughout the one minute recovery bouts between stages and two minutes following the cessation of the test. The lowest variation in heart rate during the HIMS test was observed in individuals who reached 85-90% of the maximal heart rate or >95% of the maximal heart rate. Utilizing a submaximal exercise test can be crucial for identifying clients who are under recovered. A reduction in heart rate recovery for a stable workload is a sign of reduced parasympathetic reactivation. Heart rate recovery can be effected by the intensity and duration of training, cardiac drift, dehydration and environmental factors, so it's important to track submaximal heart rate consistently with a highly repeatable test over time to establish what reduced heart rate recovery is for your client.
Practical Application of Heart Rate Monitoring
A typical training prescription consists of the following three components: frequency, volume and intensity. Heart rate monitoring allows the personal trainer to quantifiably monitor and provide feedback for the intensity of aerobic exercise. Most studies provide an imprecise estimation of classifying exercise intensity using heart rate monitoring. Stagno and colleagues used a submaximal treadmill test in male field hockey players to determine the heart rate training zones corresponding to lactate threshold and onset of blood lactate accumulation (OBLA). Lactate threshold is a defined as an exercise intensity that is associated with substantial increase in blood lactate accumulation while OBLA is the specific intensity where blood lactate levels reach 4mmol/L. From there, three more zones were determined using the physiological profiles gleaned from the submaximal test to create heart rate training zones corresponding to specific training methods.
|Zone||% Maximal Heart Rate||Training Type|
|5||93 - 100%||Maximal training|
|4||86 - 92%||OBLA training|
|3||79 - 85%||Steady-state training|
|2||72 - 78%||Lactate threshold training|
|1||65 - 71%||Moderate|
While using estimated heart rate zones can be useful initially, it is important to note there is a substantial difference between lactate threshold between trained and untrained individuals, so the best option for understanding the physiological makeup of your client is to have them tested in a lab-based setting.
The intensity of the training will dictate the nature of adaptation that occurs. Aerobic work performed below the lactate threshold will result in adaptation to the central component of the cardiovascular system, leading to improved stroke volume and cardiac output. Intensities above the lactate threshold will result in peripheral adaptations, including improved muscular capillarization, oxidative enzyme activity, mitochondrial density and volume, and preferential use of free fatty acids as an energy substrate. Heart rate monitoring is better able to assess continuous bouts of work rather than short bouts of high intensity work due to the increased contribution of anaerobic metabolism to high-intensity activities. Tracking heart rate during high-intensity running may underestimate the internal load of the work being performed.
In Part Two of this post, we'll discuss heart rate based training methods.
Nate Brookreson was named the Director of Athletic Performance for Olympic Sports at NC State University in June of 2015. Prior to his appointment, he was the Director of Olympic Sports at the University of Memphis from August 2013 until June 2015, where his primary responsibilities were with men and women's soccer, and the Director of Athletic Performance at Eastern Washington University from 2010 until 2013, where he primarily worked with football and volleyball. Brookreson played wide receiver for Central Washington University from 2001-05 and was a four time GNAC Academic All-Conference selection. He earned his Bachelor's Degree in Exercise Science from Central Washington University and his Master's Degree in Exercise Science from Eastern Washington Unviersity. He is certified (CSCS) through the National Strength and Conditioning Association, Collegiate Strength and Conditioning Coaches Association (SCCC), United State Weightlifting (USAW), and Functional Movement Systems (FMS Level 2).
1. Achten J et al. Heart rate monitoring: Applications and limitations. Sports Med, 33;517-538, 2003.
2. Buchheit M. Monitoring training status with HR measures: do all roads lead to Rome? Frontiers in Phys, 5;1-19, 2014.
3. Buchheit M. Sensitivity to monthly heart rate and psychometric measures to predict performance in highly trained handball players. Int J Sports Med, Epub ahead of print, 2014.
4. Coutts AJ et al. Practical tests for monitoring performance, fatigue and recovery in triathletes. J Sci Med Sport, 10;372-381, 2007.
5. Halson SL. Monitoring training load to understand fatigue in athletes. Sports Med, 44;139-147, 2014.
6. Hopkins WG. How to interpret changes in an athletic performance test. Sportsscience, 8;1-7, 2004.
7. Jamieson J. Ultimate MMA Conditioning. Kirkland, WA: Performance Sports Inc; 2009.
8. Jones AM et al. Cardiovascular assessment and aerobic training prescription. In: Strength and Conditioning: Biological Principles and Practical Applications. West Sussex, UK: Wiley-Blackwell; 2011:291-304.
9. Lamberts RP et al. Day-to-day variation in heart rate at different levels of submaximal exertion: Implications for monitoring of training. J Strength Cond Res, 23;1005-1010, 2009.
10. Noonan V et al. Submaximal exercise testing: Clinical application and interpretation. Phys Ther, 80;782-807, 2000.
11. Scott B et al. A comparison of method to quantify the in-season training load of professional soccer players. Int J Sports Phys Perf, 8, 195-202, 2013.
12. Smith DJ et al. Training load and monitoring an athlete's tolerance for endurance training. In: Enhancing Recovery: Preventing Underperformance in Athletes. Champaign, IL: Human Kinetics; 2002:81-102.
13. Stagno KM et al. A modified TRIMP to quantify the in-season training load of team sport players. J Sports Sci, 25;629-634, 2007.
14. Stone NM et al. Aerobic conditioning for team sport athletes. Sports Med, 39;615-642, 2009.
15. Svedahl K et al. Anaerobic threshold: The concept and methods of measurement. Can J Appl Physiol, 28;299-323, 2003.
16. Verkoshanky Y et al. Supertraining. Rome: Ultimate Athlete Concepts; 2009.
17. Vesterinen V et al. Heart-rate running speed index may be an efficient method of monitoring endurance training adaptation. J Strength Cond Res, 28;902-908, 2014.
18. Ward P. Enhancing the physiological buffer zone. Strength in Motion Performance Seminar. Kirkland, WA, 2012.