% sustainable running economy

Running economy is a term used to describe the amount of oxygen an athlete uses running a constant submaximal running speed whereas VO2max describes the rate of oxygen used by an athlete running at maximal speeds they can maintain for a period of time (5-8 minutes).

To compare athletes you will need to assess economy running at the same speeds otherwise the exercise is pointless. It can be used to compare athletes of similar VO2max (VO2max is not a very sensitive predictor of running performance amoung highly trained athletes with one another) to determine which athlete is more economical at a given speed.

% sustainable running economy I guess means the percentage of running economy an athlete is working at with a given velocity. This velocity would probably have to be predetermined to say that an athlete is working at X% of sustainable running economy with 100% being that of maximal submax velocity.

Hi Jo sorry for the delay,

I found my notes on running economy although I can only properly outline gross (GE), net (NE) and work economy (WE) for you. I did attend a seminar regarding oxygen uptake kinetics earlier this year where they spoke of sustaianble running economy in both terms of ml/kg/km and ml/kg/min. I cannot remeber the exact calculations but it would suggest that Alex is along the right lines.

GE NE WE are measured as a comparison of oxygen consumption at rest, or at a lower intensity. GE can be calculated by: work accomplished/energy expended.
To turn oxygen consumption into energy expenditure the VO2 must be converted into energy. This acheived by the following conversions 1L O2 = 5Kcals, 1Kcal = 4.18kJ. To aquire the work accomplished the load or force must be converted into the energy equivalent (1W per second = 1J).

Imagine for the sake of an easy example your testing someone one a monnark cycle ergometer. You test their oxygen consumption at rest, with zero resistence, then 30,50,70 and possibly 90 watts over a standard protocol. To determine the work accopmplished in joules, you times the load (say 50W) and convert to joules (50W x 60secs = 3000J or 3KJ). If their O2 consumption was 1.18 litres per min at this intensity, then the energy expenditure would be around 24.66 Kj (1.18L x 5 = 5.9Kcals. 5.9 x 4.18 = 24.66Kj).
Therefore if GE is work accomplished/energy expanded then 3Kj/24.66Kj = approx 12% GE.
Net Economy is calculated via Work accomplished/energy expended above rest.
Work economy is calculated via work accomplished/energy expanded above zero W.
During exercise humans are potentially upto 25% efficient (mostly due to energy lost to heat).

If you are condidering respiratory analysis (or at least its role) I would suggest you also consider Respiratory Exchange Ratio (RER).
RER is used to assess exercise intensity, and the fuels utilised for particular intensities. RER is calculated via VCO2/VO2. There tables to provide scales for results I'm sure you can find them on the net without too much trouble.

Hope this ok, feel free to ask any questions.

Cheers for that. It is appreciated.

Jo