Originally published Sept 1996
Unlike their bulky, unwieldy counterparts of the past, heart rate monitors are now sophisticated pieces of equipment, capable of providing accurate, hardcopy records of heart rates over long periods of time (up to 33 hours).
The Polar “Sport Tester” is easy to use. A comfortable, adjustable chest band (transmitter) combines with a watch style receiver in a unit that is barely discernable. Downloading the information into a computer is simple, taking around10-20 sec and provides an invaluable visual representation of heart rate during the session under review. Various calculations are performed automatically, including the assessment of time spent below, in and above the Target Heart Rate Zone and the percentage of time spent in each. (See Table 1)
Based on expired air analysis methods, various exercise intensities are proposed to be indicative of the type of fuel source being metabolised. Whilst there is some degree of conjecture as to the exact limits of this process, effective fat utilization is believed to occur in the general population at around 55%-75% of maximum heart rate levels.
The heart rate monitor provided information used to :
- Introduce and reinforce the process of heart rated exercise
- Identify the outcome of specific exercises and activities on heart rate
- Adjust and refine exercise intensities for maximal effect
- Restructure the nature/order of exercise for maximal effect
Information was collected over four sessions on the same subject, (male, mid 40’s) who had been exercising regularly for a number of years. His traditional workout consisted of strength components (dumbell/barbell exercises or machinery) combined with “Aerobic”-type machinery, (exercise bicycles, treadmills, stepping machines, rowing machines). The subject wished to spend around an hour exercising. The major aim was to reduce body fat.
From records of the subjects resting heart rate, the exercise zone limits were established at 60%-70% of maximum heart rate (as calculated from Karvonen principles), and the unit adjusted to sample heart rate every 5 seconds. Sampled heart rate records included warm up and cool down periods.
As can be seen from illustration 1, the initial workout, whilst utilising energy, spent a significant period of time below the Target Heart Rate Zone. 
The visual record reinforced to the subject exactly what happened in regard to heart rate when he exercised, and the effect of both the “rest periods” and of the utilisation of the strength component of the program.
Illustration 2, records the second session, where the exercise pattern was repeated, with exercise intensity adjusted to levels which were estimated to bring the response into the Target Heart Rate Zone.
Effectively, this transposed the original record ‘upwards’, as modified intensities resulted in higher heart rate responses. As can be seen, the Target Heart Rate Zone was in fact overshot in many instances.
In the third session, (illustration 3), the subject was asked to attempt to maintain heart rate within the calculated Target Heart Rate Zone, by adjusting the intensity of the exercise gradually. This was simple to achieve, as he was now familiar with the process and could regularly and instantaneously monitor his heart rate from the watch, which displayed it continuously.
This resulted in less time spent above the Target Zone, where the subject felt discomfort and more significant periods of time spent in the Target Heart Rate Zone. At this stage the subject's motivation began to improve significantly.
With the intensities of the exercises now identified, the program’s order was adjusted and the volumes adjusted (illustration 4).
The exercise bicycle’s steady climb component was replaced by a more constant and thus appropriate selection, the strength aspect was eliminated (as the subject’s priority was to lose body fat) and the duration of some of the exercises increased. The subject found the intensities well manageable but challenging. The resultant analysis reinforced his feelings, with a flatter, more constant heart rate curve, now more consistently in the Target Heart Rate Zone.
This has resulted in a more effective use of workout time. From an initial 85% (55 min 45sec) of time spent below optimal heart rate for his desired outcome, the subject now spent only 33%(19min15sec), remembering that these times include warm-up and cool down periods. More importantly, his workout now resulted in 45% of the workout completed in the Target Heart Rate Zone and 22%manageably above it compared to his initial12% in and 3% above.
TABLE 1
Summary of Sampled heart rate data
Time %Above %In %Below Time In Time Below
Session 1 65:20 3 12 85 0:07:20 0:55:45
Session 2 63:25 18 31 51 0:19:35 0:32:05
Session 3 58:40 2 34 64 0:19:50 0:37:30
Session 4 57:40 22 45 33 0:25:25 0:19:15
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Regards Kym
