Course:KIN366/ConceptLibrary/Target Heart Rates

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Movement Experiences for Children
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KIN 366
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Instructor: Dr. Shannon S.D. Bredin
Email: shannon.bredin@ubc.ca
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The main purpose of this page is to enhance the readers understanding of target heart rates as it pertains to improving physical fitness and its applicability to improving the movement experiences of children. There will not be a major emphasis on detailed exercise physiology as it relates to the topic because it is beyond the scope of our focus. However general physiological information required in order understanding the topic will be briefly explained. The concept of target heart rates will be explained including how to calculate individualized target heart rate zones and applications in the field setting.

Heart Rate and Physical Activity

What is heart rate?

The most basic definition of heart rate is the speed at which the heart beats, typically measured in beats per minute or bpm (Plowman & Smith, 2011). Resting heart rate (RHR) refers to our heart rate during resting conditions such as when we have just woken up from slumber whereas maximum heart rate (MHR) refers to the highest rate an individual can achieve based upon their age (Brown & Chandler, 2013). The process of obtaining these values will be examined in subsequent sections.

How does heart rate relate to physical activity and exercise?

Increased heart rate is a cardiovascular response to physical exercise (ie: running, swimming, and skipping). It has a linear relationship with exercise intensity—as exercise intensity increases, heart rate also continues to increase until it plateaus or reaches maximum heart rate (Plowman & Smith, 2011). Heart rate elevates with increased intensity because there is an increased demand for energy (in the form of ATP—adenosine triphosphate) which is derived through aerobic metabolism (breakdown of substrates to form ATP with oxygen) and anaerobic metabolism (breakdown of substrates to form ATP without oxygen), processes that require an elevated heart rate (Plowman & Smith, 2011). Both these systems work together all the time but one system or the other will predominate depending on the intensity of exercise.

How can heart rate be used to improve athletic performance and physical fitness?

First it is important to note the training principle (fundamental guidelines that form the basis for the development of an exercise training program) of overload (one training principle among others) which states that in order to improve physical fitness, one`s training regimen must induce overload—an exercise or training stimulus that goes beyond the normal capabilities of the person, thus forcing the body to adapt (Brown & Chandler, 2013). For example if an individual wants to be able to run 4 miles but can only run 1 mile, his or her program may start at a 1 mile distance but must overload to 1.5 miles, 2 miles 3 miles and eventually 4. One way to monitor overload is by manipulating exercise intensities through the monitoring of lactic acid (a by-product of anaerobic metabolism) (Plowman & Smith, 2011). More specifically we can calculate the onset of blood lactate accumulation (OBLA) or lactate threshold—the specific intensity at which the body produces more lactic acid than it can clear, resulting in an accumulation or buildup of the anaerobic by-product, which causes performance decrements (Plowman & Smith, 2011). OBLA is variable between people and it is indicative of fitness levels (Brown & Chandler, 2013). This value is the transition from predominantly using aerobic systems to predominantly using anaerobic systems. Therefore by knowing this value, we can manipulate intensities depending on whether we want to train aerobically or anaerobically, both of which result in different adaptations. Ideally we would want to monitor lactic acid levels using direct samples of blood but this can be very inconvenient for the athlete who has to constantly stop to take blood lactate levels and equipment can be expensive (Plowman & Smith, 2011). This is where the use of heart rates may be useful. An individual’s lactic acid levels is correlated to the intensity of exercise and thus also correlated to heart rate (Plowman & Smith, 2011). Monitoring heart rate with a heart rate monitor is generally easier and more convenient for the athlete than monitoring blood lactate levels therefore we can use heart rate as an indirect measure of lactate levels and monitor exercise intensities in order to improve performance and physical fitness.

Target Heart Rate and Heart Rate Zones

What are target heart rates?

The term target heart rate refers to specific heart rates which the individual tries to maintain for a specified amount of time during an exercise regimen. Generally, long term training (months to years) results in physiological adaptations in the body as a response to exercise (Centers for Disease Control and Prevention, 1999). This includes musculoskeletal, cardiovascular, respiratory, endocrine, and immune system adaptations which allow the body to perform at higher levels (Centers for Disease Control and Prevention, 1999). As we have mentioned in the previous section, training aerobically or anaerobically yields different adaptations. However, we can become more specific than just aerobic and anaerobic classifications. Aerobic and anaerobic training can be divided into heart rate zones which yield specific adaptations (ie: training in one target heart rate zone yields specific adaptations whereas training in another target heart rate zone yields predominantly different adaptations). Target heart rate zones are based on a percentage of the heart rate at the OBLA (Plowman & Smith, 2011). Subsequent sections will show how to calculate these heart rate values.

The 5 heart rate zones

The five target heart rate zones listed below include simple examples of how it could be applied to a running program. However, this may be applied to other types of training such as biking and swimming. It is also important to point out that while specific adaptions are predominant in specific heart rate zones, there is plenty of overlap involved. For example training in zone 3 predominantly increases maximal oxygen uptake but the other zones may also contribute to its improvement.

Zone 1: Recovery, less than 85% of OBLA (Plowman & Smith, 2011)

  • Training in zone 1 does not yield significant physiological adaptations for improving athletic performance because it is a very low intensity. This zone can be used to warm up or cool down before and after major workouts.
  • Workout example: 20-30 minute aerobic exercise at this zone (ie: very light jog)

Zone 2: Extensive Aerobic, 85-90% of OBLA (Plowman & Smith, 2011)

  • Zone 2 training increases an athlete`s endurance base through mitochondrial biogenesis (increasing the number of mitochondria in the muscles) (Hood, 2009). Training in this zone allows for greater frequency and longer durations which lead to a greater volume of training (Plowman & Smith, 2011).
  • Workout example: long slow distance, 30 minute – 2 hours continuous aerobic exercise at this zone (long distance, slow pace run)

Zone 3: Intensive Aerobic, 90-95% of OBLA (Plowman & Smith, 2011)

  • Zone 3 training improves maximal oxygen uptake (VO2max) which is the maximum rate at which an individual can consume oxygen and is a major influence on aerobic performance (Gormley et al., 2008)
  • Workout example: 5-10 minute intervals of aerobic exercise at this zone (faster paced runs)

Zone 4: Lactate Threshold or Extensive Anaerobic, 95-105% of OBLA (Plowman & Smith, 2011)

  • Zone 4 training, sometimes known has threshold training, improves the OBLA (Sjodin, Jacobs, & Svedenhag, 1982). As noted earlier, training above the OBLA results in accumulation of lactic acid. Eventually, the accumulation results in performance decrements, therefore improving OBLA is a major performance variable because having a higher lactate threshold than another athlete means that the accumulation of lactic acid occurs at a higher intensity and at a later time.
  • Workout example: 2-5 minute intervals of anaerobic exercise at this zone (near maximal speed)

Zone 5: Intensive Anaerobic (above 105% of OBLA) (Plowman & Smith, 2011)

  • Training in zone 5 increases tolerance for lactic acid if the recovery time between intervals does not allow for complete recovery (Plowman & Smith, 2011).
  • Workout example: 10 second – 2 minute intervals of intense anaerobic exercise at this zone (maximal speed), less than 3 minute rest intervals

Calculating Individualized Target Heart Rate Zones

Determining lactate threshold

In order to determine the target heart rate zones, OBLA must first be determined. With expensive equipment, the most accurate way of determining lactate levels is through invasive and direct methods of monitoring lactate in the blood (Plowman & Smith, 2011). However most coaches, parents, and teachers do not have access to such equipment and other non-invasive techniques must be used. Conconi`s determination is one non-invasive method for determining OBLA. Using heart rate recordings from a graded exercise test, Conconi`s method describes the OBLA as the deflection point (point at which heart rate deflects or deviates from its linear course) on a heart rate vs intensity plot (Conconi et al., 1996). The following are a list of steps to determine lactate threshold using Conconi`s determination using a treadmill test (note: there are also protocols for cycle ergometers):

1. Determine the subject’s predicted MHR using the following equation: MHR (bpm) = 208 - [0.7 x age (yr)] (Plowman & Smith, 2011). MHR is independent of age from ages 6-16 and this equation cannot be used for this group (Plowman & Smith, 2011). During this age span, the average MHR from treadmill running is 200-205 bpm (Plowman & Smith, 2011).

2. Calculate 95% of MHR

3. Have subject adequately warm-up for about 5-10-min at a suitable intensity

4. Strap on a heart rate monitor and make sure you are getting a signal (read the instructions that come with your heart rate monitor)

5. a) Set the initial intensity of the treadmill to a slow speed, such as 3-3.5 mph

b) Increase the intensity each minute by 0.5 mph

c) At the end of each minute record the participants heart rate using the following table:

Time (min) Heart Rate (bpm) Running speed (mph)
1 3
2 3.5
3 4
4 4.5
5 5
6 5.5
7 6
8 6.5
9 7
10 7.5
11 8

d) Terminate the test when (1) the subject has reached 95% of MHR and no heart rate deviation has occurred, or, (2), you notice a definite deviation in HR vs intensity during the test on the subject before he/she has reached 95% of MHR, or, (3), the subject reaches volitional fatigue.

6. Graph heart rate on the Y-axis and workload on the X-axis (this graph is known as a lactate curve)

a. From the graph look for a deflection in the heart rate with increasing workload intensity

b. Draw a line of best fit through the linear increases in HR (leave off the last few data points, 3 or 4) and extend the best fit line to the top of the graph

c. Draw a curvilinear line through the remaining data points (those left off the straight line plot)

7. Where the curvilinear line intersects the linear line is the “deflection point”, or the point where the heart rate deflects off the linear pattern. This deflection point is the OBLA.

The following is an example of this method used on a 23 year old male subject with the corresponding steps from above:

Step 1. MHR = 208 – (age 23 yrs * 0.7) = 192 bpm

Step 2. 95% of Maximum Heart Rate = 0.95 * 192 bpm = 182 bpm

Step 5c. Data collection:

Time (min) Heart Rate (bpm) Running Speed (mph)
1 105 3
2 108 3.5
3 121 4
4 127 4.5
5 146 5
6 160 5.5
7 162 6
8 173 6.5
9 179 7
10 182 7.5
11 187 8

Step 6+7.

Example of lactate threshold using collected data from above



















Calculating target heart rate zones using the calculated OBLA

Once the OBLA has been calculated we can then calculate the target heart rate zones using Karvonen`s heart rate reserve (HRR) method which has the advantage of considering resting heart rate (Plowman & Smith, 2011). We can also predict corresponding treadmill speeds based on the graph. The steps for the HRR method are as follows:

1. Calculate resting heart rate by using a heart rate monitor or taking the pulse for 30 seconds and multiplying that value by 2 to get bpm. It is best to measure resting heart rate in the morning after waking up.

2. Determine the HRR by subtracting the RHR from the MHR (for the purposes of target heart rate zones, the maximum heart rate is the OBLA): HRR = HRmax (OBLA) – RHR

3. Choose the desired intensity of the workout (the intensities we will use are the percentages of OBLA derived from the heart rate zones).

4. Multiply the percentages for the lower and upper heart rate limits by the HRR and add RHR

The following is an example using the calculated OBLA value of 171 bpm (from the previous section) and a RHR of 65 bpm:

Step 1. RHR = 65 bpm

Step 2. HRR = 171 – 65 = 106 bpm

Steps 3+4.

Zone 1 (Less than 85% of OBLA)

  • (0.85)(106) = 90 + 65 = 155 bpm
  • Zone 1 = less than 155 bpm
  • Predicted treadmill speed: Less than 5.5 mph

Zone 2 (85-90% of OBLA)

  • (0.85)(106) = 90 + 65 = 155 bpm
  • (0.90)(106) = 95 + 65 = 160 bpm
  • Zone 2 = 155 – 160 bpm
  • Predicted treadmill speed: 5.5 – 5.8 mph

Zone 3 (90-95% of OBLA)

  • (0.90)(106) = 95 + 65 = 160 bpm
  • (0.95)(106) = 101 + 65 = 166 bpm
  • Zone 3 = 160-166 bpm
  • Predicted treadmill speed: 5.8 – 6.1 mph

Zone 4 (95-105% of OBLA)

  • (0.95)(106) = 101 + 65 = 166 bpm
  • (1.05)(106) = 111 + 65 = 176 bpm
  • Zone 4 = 166-176 bpm
  • Predicted treadmill speed: 6.1 – 6.6 mph

Zone 5 (above 105% of OBLA)

  • (1.05)(106) = 111 + 65 = 176 bpm
  • Zone 5 = above 176 bpm
  • Predicted treadmill speed: 6.6 mph +

Application to the Improvement of Children’s Movement Experiences

Target heart rates can be used by coaches, parents and teachers to improve a specific aspect of a child’s fitness for the purpose of improving athletic performance. It can be used as a way to target a child’s specific weaknesses and improve upon them. For example a coach may observe that Jimmy has great endurance but cannot run near maximal speeds for adequate amounts of time. This would indicate that Jimmy may need more training in heart rate zones 4 and 5.

Target heart rates can also be used in the designing of sports programs. Coaches can look at which heart rate zone their sport is primarily played in and they can design their practices so that those heart rate zones are targeted. One of the weaknesses in a team setting is that you would need many heart rate monitors (which can be very expensive). It would take a considerable amount of time to calculate the target heart rate zones for each member of a team. However a coach, parent, or teacher with the knowledge of target heart rate zones can still design practices or programs with specific purposes based upon this knowledge.

Furthermore, target heart rates can be used to track improvements or decreases in fitness which would predict improvements or decrements in performance. We can monitor this by monitoring an individual’s lactate curve. As mentioned earlier, training in zone 4 predominantly improves OBLA indicating improved fitness and performance. On the lactate curve we would observe a shift of the right meaning that the lactate threshold occurs at a greater intensity and at a later time point. A shift to the left would indicate detraining or a loss in fitness and thus a decrement in performance. This is because the lactate threshold occurs at an earlier time point, at a lower intensity.

References

Brown, L., & Chandler, T. (2013). Conditioning for strength and human performance (2nd ed.). Philadelphia, PA: Lippincott Williams & Wilkins.

Centers for Disease Control and Prevention. (1999). Physiologic responses and long-term adaptations to exercise. Retrieved from http://www.cdc.gov/nccdphp/sgr/pdf/chap3.pdf

Conconi, F., Grazzi, G., Casoni, I., Guglielmini, C., Borsetto, C., Ballarin, E., ... Manfredini, F. (1996). The Conconi test: Methodology after 12 years of application. International Journal of Sports Medicine, 17(7), 509-19. doi:10.1055/s-2007-972887

Gormley, S., Swain, D., High, R., Spina, R., Dowling, E., Kotipalli, U., & Gandrakota, R. (2008). Effect of intensity of aerobic training on VO2max. Medicine & Science in Sports & Exercise, 40(7), 1336-1343. doi: 10.1249/MSS.0b013e31816c4839

Hood, D. (2009). Mechanisms of exercise-induced mitochondrial biogenesis in skeletal muscle. Applied Physiology, Nutrition, and Metabolism, 34(3), 465-472. doi: 10.1139/H09-045

Plowman, S., & Smith, D. (2011). Exercise physiology for health, fitness, and performance(3rd ed.). Baltimore, MD: Lippincott Williams & Wilkins.

Sjodin, B., Jacobs, I., & Svedenhag, J. (1982). Changes in onset of blood lactate accumulation (OBLA) and muscle enzymes after training at OBLA. European Journal of Applied Physiology and Occupational Physiology, 49(1), 45-57. Retrieved from http://www-ncbi-nlm-nih-gov.ezproxy.library.ubc.ca/pubmed/?term=Changes+in+onset+of+blood+lactate+accumulation+(OBOB)+and+muscle+enzymes+after+training+at+OBLA