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HEART RATE MONITORING

The Role of Polar Heart Rate monitors within the PGMOL

The use of Polar Heart Rate monitors (HRM) is one of the best ways to monitor training and match loads as they are practical to use and provide immediate feedback.
 
The main benefit of the Polar HRM’s to the PGMOL is that the monitors and the Polar Precision software permit the analysis of our match officials training sessions. The heart rate (HR) data collected by the monitors provides an examination of whether or not match officials are meeting goals of the training sessions that we have prescribed. For example, high intensity aerobic training sessions should be performed at an intensity corresponding to 86 – 95% of the match officials’ maximum heart rate (HRmax). Whereas, for speed training, we use the HRM’s to ensure the physical load is kept to a minimum and that recovery is complete in between sprint repetitions. The HRM’s allow the match officials to monitor their training intensity throughout the session and the download facility via the software enables the Sports Scientist to evaluate the match officials’ weekly training programmes.
 
All PGMOL match officials wear the RS400 Polar HRM during matches as well as during training sessions. This data provides a valuable insight into the physical demands placed upon match officials during matches and in turn permits the Sports Scientists to prescribe match specific training loads. The combination of heart rate monitoring during training and matches helps us to ensure that our match officials are optimally prepared, which will in turn enable them to keep up with play and obtain optimal viewing positions throughout the duration of their matches.
 
However, in order for accurate and reliable interpretation of HR training data, there are a number of factors can affect HR during exercise and these need to be controlled for.
 

Dehydration

HR’s are elevated during exercise in high ambient temperatures, when compared to exercise in cooler environments, with the rise in HR compensating for the extra fluids that are lost during sweating. However, increasing levels of dehydration will impair physical performance. Research has demonstrated that only a 1% loss in body weight owing to sweat losses is enough to impair performance, with further performance decrements being directly related to the amount of dehydration accrued.

 
Also, after the first few minutes of mild to moderate intensity exercise there is a gradual increase in HR as exercise progresses, termed cardiovascular drift – increases of up to 15% from 5 - 60` of exercise have been reported.4 This again is related to level of dehydration incurred during exercise.  Therefore, when aiming for a certain HR zone during exercise this drift should be considered.4
 

Time of Day

Reilly et al. 5 reported a considerable diurnal variation (5 - 15% variation across a 24hour period) on HR, with HR responses being highest late in the afternoon / early evening. This is consistent with exercise performance being at its peak during the same time of day.
 
 
 

0300

0900

1500

2100

HRrest

90

96

99

96

HRmax

176

180

182

182
 

Anxiety

Psychological stress has been shown to increase HR with minimal physical activity.

Competition

During a competitive match, a referee’s HR response is likely to be affected by factors such as environmental conditions and emotional stress. Consequently, HR’s recorded during matches may overestimate the actual amount of physical work undertaken by a referee. Therefore, competitive HR’s will tend to be higher than training HR’s. The data below collected from runners clearly demonstrates this:

 

10km

21km

42km

HR during race

163

166

156

HR during training

143

151

137

Day to Day Variation

Astrand and Saltin6 reported a day to day variation of 3beats.min-1 difference for steady state exercise. Whereas, Brisswater and Legros7 studied national class runners on a treadmill at sub maximal speed and reported a day to day variation of 6beats.min-1!

Effect of Training

The illustration aboe demonstrates the effect of training upon HR at rest, during sub maximal and maximal exercise. Therefore, HR monitoring during graded exercise can be used to assess changes in fitness status.

HR Monitoring during Training
 
When undertaking fitness training, especially intensive training sessions, it is best that HR is expressed relative to each individual referee. The reason for this is that referees of different ages and different fitness levels can attain the appropriate physiological overload from their training sessions. In order to achieve this, it is necessary to have HRmax accurately determined so that HR during training, and matches, can be expressed as a percentage of this value. This is also a very easy way to prescribe training intensities as a % of HRmax.
 
HRmax can be determined via a maximal effort on a fitness test, either laboratory or field based, or taken as the highest 5second peak attained in a match or during an intensive training session. However, it is important that this figure is reliable otherwise the goals of a particular training session, if using HR’s to monitor the training load, will not be met. Therefore, it is important that the figure, which represents HRmax, is the highestrecorded during any of the above sessions. 
 
In situations where one value is significantly higher that all other peaks, it is necessary to check the HR readings carefully to ensure that this figure is not an error. If the value appears to be true, then it may be that a central mean HRmax value is used from the highest 5second peaks attained during fitness tests, matches and intensive training sessions. This will minimise the potential risk of under or over estimation when calibrating exercise intensities with HR.8  It is also necessary to monitor HRmax directly throughout the training year, perhaps once every 2 months as HRmax can be sensitive to training status.9 
 
Once an accurate and reliable HRmax has been determined, it is possible to add HR zones into the training monitoring process. Therefore, training is prescribed as a range as opposed to a fixed figure.
 
Heart Rate Zones

%HRmax

Type of Training

Perceived Exertion

Below 60%HRmax

Recovery

Very Easy

60 - 75%HRmax

Low Intensity

Easy to Comfortable

76 - 85%HRmax

Medium Intensity

Uncomfortable to Slightly Hard

86 - 93%HRmax

High Intensity

Hard to Very Hard

Over 93%HRmax

Maximal Effort

Maximal!!!

In summary, HR monitoring offers one of the best and easiest ways to monitor training load as they are practical to use, relatively cheap and provide immediate feedback, which enables the individual referee / coach / sports scientist to:

 
i) Objectively assess the physical effort during all training sessions.
ii) To ensure that the aims of individual training sessions are met.
iii) To ensure that training sessions are varied in terms of duration and intensity, and, most importantly, that the referees’ training load is tapered (gradually reduced) towards matches.
iv) Ensure an appropriate level of all-round physical fitness is developed which will enable a referee to meet the physical demands of their matches.
 
References
 
1. Gilman, M.B. (1996) The use of heart rate to monitor the intensity of endurance training. Sports Medicine, 21 (2), 73-79.
2. Laukkanen, R.M.T. and Virtanen, P.K. (1998) Heart rate monitors: state of the art. Journal of Sports Sciences, 16, S3-7.
3. Wilmore J.H. and Costill, D.L. (1999) Physiology of Sport and Exercise. 2nd Edition. Human Kinetics:Illinois, pp394.
4. Achten, J. and Jeukendrup, A.E. (2003) Heart rate monitoring. Applications and limitations. Sports Medicine, 33 (7), 517-538
5. Reilly, T., Robinson, G. and Minors, D.S. (1984) Some circulatory responses to exercise at different times of day. Medicine and Science in Sports and Exercise, 16, 477-482.
6. Astrand, P.-O. and Saltin, B. (1961) Oxygen uptake during the first minutes of heavy muscular exercise. Journal of Applied Physiology, 16, 971-976.
7. Brisswalter, J. and Legros, P. (1994) Daily stability in energy cost of running, respiratory parameters and stride rate among well-trained middle distance runners. International Journal of Sports Medicine, 15, 238-241
8. Boudet, G., Garet, M., Bedu, M., Albuisson, E. and Chamoux, A. (2002) Median maximal heart rate for heart rate calibration in different conditions: laboratory, field and competition. International Journal of Sports Medicine, 23, 290-297.
9. Zavorsky, G.S. (2000) Evidence for possible mechanisms of altered maximum heart rate with endurance training and tapering. Sports Medicine, 29 (1), 13-26.
 
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