Modeling Charge / Discharge Kinetics of the W' During Intermittent Exercise: 967: June 3 8:30 AM - 8:45 AM

Skiba, Philip F.; Chidnok, Weerapong; Vanhatalo, Anni; Jones, Andrew M. FACSM

Medicine & Science in Sports & Exercise:
doi: 10.1249/01.MSS.0000403096.31130.8d
E-18 Free Communication/Slide - Sport Science: JUNE 3, 2011 8:00 AM - 10:00 AM: ROOM: 401
Author Information

University of Exeter, Exeter EX12LU, United Kingdom.


(No relationships reported)

The Critical Power model concerns the relationship between work rate (P, in watts) and fatigue, and includes two constants: the CP and the W'. These are related according to the equation (Whipp 1982): W' = (P-CP)t

The CP is a power that can be maintained indefinitely on the basis of "aerobic" metabolism. The W' is a finite work capacity (in joules) available above CP (i.e. in the final sprint of a bicycle race), which is recharged curvilinearly (Ferguson 2010). Depletion of the W' results in extreme fatigue. Thus, knowledge of the W' can be helpful when developing a race strategy (Fukuba and Whipp 1999).

PURPOSE: To develop a function to account for the kinetics of the W' during intermittent exercise, permitting constant monitoring of the athlete's "W' balance" remaining.

METHODS: After determining GET, VO2max, CP and W', 6 recreationally active subjects carried out 5 separate exercise tests on an electronically braked ergometer. Each set was repeated until fatigue.

1: 60s of severe intensity exercise with 30s of 20W recovery

2: 60s of severe intensity exercise with 30s of moderate recovery

3: 60s of severe intensity exercise with 30s of heavy recovery

4: 60s of severe intensity exercise with 30s of severe recovery

5: A constant power trial in the severe domain

The data were fit to the equation:

where (t-u) = time between samples resulting in a depletion of W', and tc is the time constant of recharge, dependent on recovery power. The tc was varied by an iterative process until modeled W'balance = 0 at the time of fatigue. Derived time constants were plotted against %CP during recovery.

RESULTS: Below CP, time constants of W' recharge were correlated with recovery power (r = 0.73). There was no correlation if recovery power exceeded CP. Time constants of W' recharge were correlated with the CP during 20W recovery (avg = 369s, SD = 23s, r = 0.86), moderate recovery (avg = 504s, SD = 115s, r = 0.55) and heavy recovery (avg = 579s, SD = 114s, r = 0.69), but not severe recovery or continuous severe exercise.

CONCLUSION: It is possible to model the discharge and recharge of the W' during intermittent exercise. This could have important implications for the planning and real time monitoring of athletic performance.

© 2011 American College of Sports Medicine