The critical velocity in swimming

Area of Science:

• Sports Science
• Exercise Physiology
• Biomechanics

Background:

• The conventional critical velocity (cv) calculation assumes constant energy cost and immediate maximal oxygen uptake (VO2max).
• This model, derived from distance (d) versus time (t) plots (d = I + St), may not accurately reflect supra-maximal exercise performance.
• In swimming, the energy cost of locomotion (C) is known to increase with velocity, violating a key assumption of the traditional cv model.

Purpose of the Study:

• To investigate the validity of the conventional critical velocity (cv) calculation in swimming.
• To propose and validate a method for calculating cv and anaerobic distance (d(anaer)) in swimming, accounting for velocity-dependent energy cost.
• To compare the results from the conventional method with the proposed method using elite swimmers' data.

Main Methods:

• Calculated cv and d(anaer) using published data from elite male swimmers across four strokes (butterfly, backstroke, breaststroke, front crawl) over various distances (45.7m, 91.4m, 182.9m).
• Determined swimmers' VO2max and their specific C versus velocity (v) relationships.
• Compared the novel cv and d(anaer) values with those derived from the traditional I (anaerobic distance) and S (speed) calculations.

Main Results:

• The conventional method yielded a higher speed (S) and lower anaerobic distance (I) compared to the proposed method's cv and d(anaer).
• Calculated cv was consistently lower than S across all strokes (4-16% difference).
• The anaerobic distance (d(anaer)) increased with the swim distance, and was significantly larger than the conventionally estimated I.

Conclusions:

• The conventional critical velocity calculation method should be used with caution when evaluating swimming performance due to its underlying assumptions.
• A revised approach is necessary to accurately determine critical velocity and anaerobic contributions in swimming, considering the variable energy cost.
• The proposed method provides a more accurate assessment of physiological capacity and performance in elite swimmers across different strokes and distances.