Friday 21 November 2014

The Effects of Age on Functional Threshold Power

Dr Coggan wrote a very good piece on how Functional Threshold Power declines with age here:
Successful Aging and Functional Threshold Power
The conclusion being that FTP w/kg declines on average at 0.04 w/kg/yr after 40 years old. After the FTP test at our club this week (see previous post) we were discussing how to compare the results of the younger guys with us old war horses.

It seemed to me that I might answer the question from another direction using the Veteran Time Trial Association Standards Tables and the well known equation for power (Martin et al 1998):
(g is Earth's gravity, m mass of rider+bike, Vg speed over ground, K1 is a constant representing rolling resistance, s slope, K2 a constant representing drag, Va is speed through the air)
I made some reasonable assumptions - flat course, still conditions, rider of 75kg and 8 kg bike, etc. and arrived back at exactly the same result for both men and women! I varied the rider and bike mass and the results did not vary to a significant degree. Whilst my results validated the average reduction per year, it was not linear. Up to age 65 average reduction per year was less than 0.04. After 65 it increased quite rapidly as shown in the graph below:

So at age 55, my FTP/kg of 2.85 is comparable to 3.45w/kg for a <40 year old. To arrive at your own age adjusted w/kg subtract 40 from your age and multiply by 0.04 then add to your FTP/kg. If you want to know how you compare to others you can then look yourself up in the table prepared again by Dr Coggan:

Maximal power output (in W/kg)
MenWomen
5 s1 min5 minFT5 s1 min5 minFT

24.0411.507.606.4019.429.296.615.69
23.7711.397.506.3119.209.206.525.61
23.5011.277.396.2218.999.116.425.53
23.2211.167.296.1318.779.026.335.44
World class22.9511.047.196.0418.568.936.245.36
 (e.g., international pro)22.6810.937.085.9618.348.846.155.28
22.4110.816.985.8718.138.756.055.20
22.1410.706.885.7817.918.665.965.12
21.8610.586.775.6917.708.565.875.03
21.5910.476.675.6017.488.475.784.95
Exceptional21.3210.356.575.5117.268.385.684.87
 (e.g., domestic pro)21.0510.246.465.4217.058.295.594.79
20.7810.126.365.3316.838.205.504.70
20.5110.016.265.2416.628.115.414.62
20.239.896.155.1516.408.025.314.54
19.969.786.055.0716.197.935.224.46
Excellent19.699.665.954.9815.977.845.134.38
 (e.g., cat. 1)19.429.555.844.8915.767.755.044.29
19.159.435.744.8015.547.664.944.21
18.879.325.644.7115.327.574.854.13
18.609.205.534.6215.117.484.764.05
18.339.095.434.5314.897.394.673.97
Very good18.068.975.334.4414.687.304.573.88
 (e.g., cat. 2)17.798.865.224.3514.467.214.483.80
17.518.745.124.2714.257.114.393.72
17.248.635.014.1814.037.024.303.64
16.978.514.914.0913.826.934.203.55
16.708.404.814.0013.606.844.113.47
16.438.284.703.9113.396.754.023.39
Good16.158.174.603.8213.176.663.933.31
 (e.g., cat. 3)15.888.054.503.7312.956.573.833.23
15.617.944.393.6412.746.483.743.14
15.347.824.293.5512.526.393.653.06
15.077.714.193.4712.316.303.562.98
14.797.594.083.3812.096.213.462.90
Moderate14.527.483.983.2911.886.123.372.82
 (e.g., cat. 4)14.257.363.883.2011.666.033.282.73
13.987.253.773.1111.455.943.192.65
13.717.133.673.0211.235.853.092.57
13.447.023.572.9311.015.763.002.49
13.166.903.462.8410.805.662.912.40
Fair12.896.793.362.7510.585.572.822.32
 (e.g., cat. 5)12.626.673.262.6610.375.482.722.24
12.356.563.152.5810.155.392.632.16
12.086.443.052.499.945.302.542.08
11.806.332.952.409.725.212.451.99
11.536.212.842.319.515.122.351.91
Untrained11.266.102.742.229.295.032.261.83
 (e.g., non-racer)10.995.992.642.139.074.942.171.75
10.725.872.532.048.864.852.071.67
10.445.762.431.958.644.761.981.58
10.175.642.331.868.434.671.891.50
As you will see my 2.85 put me between Fair and Moderate. Age adjusted increases this to the lower end of Good. Given that I am finishing in the middle of my age group on ironman distance bike legs, that seems about right.

1 comment:

  1. Thank you for the above charts, very interesting and helpful.
    Strictly speaking, to create an age adjusted FTP one should divide one's FTP with the value from the above chart. For example, both lines above show a 50% deterioration by about age 84. If someone has an FTP of one, that would give them an age adjusted FTP of 2 (1 / 50%), while someone with an FTP of 3 would have an age adjusted FTP of 6 (3 / 50%). The adjustements being 1 and 3, depending on one's current FTP. In contrast, the suggested calculation above would increase both of the FTPs by 1.8. This would only be correct for an 84 year old having a current FTP of 1.8.

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