Power Work Capacity Assessment
Increasing physical work capacity is a basic element of any athletic training program. Therefore, an objective quantitative assessment of physical work capacity can be an important tool in measuring the effectiveness of training.
Physical work capacity is primarily determined by the coordinated functioning of the neuro-muscular, cardio-respiratory, and energy producing systems. The functioning of these systems is coordinated by the regulating influences of the autonomic and central nervous systems. While it is possible to assess the regulating influences (adaptive reactions) at rest using Omegawave’s Heart Rate Variability, Omega, and Sensorimotor assessments, it is difficult to assess the interaction of the of the systems that determines physical work capacity at rest. That is why loading tests are used for assessing physical work capacity.
The principal of measuring physical work capacity is simple. Work capacity equals power multiplied by time. If you set one of these parameter and measure another, you can calculate the third.
One method for assessing physical work capacity is to set an ergometer for a constant power output with a constant speed and measure the time an athlete can maintain that power output before reaching exhaustion. If the test is repeated at a later date and the time to exhaustion has increased, the athlete’s physical work capacity has increased.
While this method of assessment is used for diagnostic purposes, it has limited use in sports. This is because, from a practical stand point, working to exhaustion cannot be used repeatedly during a training or competitive season because of the impact it would have on the athlete.
Research conducted by T. Sjostrand at Karpolinsky University in the 1950s suggested a sub-maximum test measuring the power of physical activity (Bt) at a heart rate of 170 beats per minute (bpm) can a reliable assessment of physical work capacity. This is because:
1. A heart rate of 170 bpm marks the beginning of the optimal zone for the function of the cardio-respiratory system in response to physical activity.
2. There is a linear relationship between heart rate and physical activity for the range between approximately 105-110 bpm and 170 bpm. The relationship between heart rate and the power of physical activity ceases to be linear above 170 bpm.
As originally designed, PWC170 tests required subjects to complete five to seven stages of exertion lasting six minutes each. Later studies by Karpman and others resulted in development of the Shestrand method that reduced testing time considerably by utilizing only two sessions of load at moderate power. The duration of the first load is five minutes which is sufficient time for the heart to reach a steady state of work. Then there is a three minute rest period after completion of the first load. Then there is a second five minute period of exertion. Heart rate in bpm is recorded for 30 seconds after each period of exertion. The power output for the load is set based on the subject’s weight and level of fitness.
A linear plot of heart rate vs. load is constructed from the data from the two periods of exertion and is used to calculate a PWC170 value.
By collecting heart rate data for three minutes after completion of the second load, it is possible to assess rehabilitation processes.
The modified PWC170 method has been used by Karpman and other researchers in testing several thousand athletes at various levels of preparation in 25 different sports. Reliable correlation between PWC170 and VO2max, as well as the volume of left ventricle of the heart and cardiac output has been reported.
Based on the body of research, PWC170 can be considered a valid method for assessing general physical work capacity in athletes with an emphasis on assessing aerobic reserves. The advantages of the PWC170 method are that it is safe, can be done in a relatively short amount of time (16 minutes), and only requires moderate loads so that there is little or no impact on normal training. The benefits of the PWC170 method are that it can be done at any stage of athlete preparation without compromising the quality of training and that when PWC170 assessments are done over time, they provide insight into the adequacy of training methods at each stage of the athlete’s preparation.