Swimming long, and swimming high: a case study on the physiology and training behind a record-setting swim across Lake Tahoe

Purpose: We described the physiological adaptations evoked during a 4 month training block in an elite female swimmer building towards two ultraendurance races: (1) a 16.1 km solo swim at sea level, and (2) a 34.3 km solo swim at 1900 m (~6200 ft) of elevation. Methods: The athlete underwent regular physiological assessments including measures on resting metabolic rate, peak oxygen uptake (V̇O2peak), exercise economy, and grip strength. In addition to training and pre-race measures, we captured the physiological responses immediately following completion of the 34.3 km distance. Results: The athlete completed 1.8 km of the 16.1 km ultraendurance swim in San Francisco before dropping out with symptoms of vertigo. One month later the participant completed the 34.3 km ultraendurance race across Lake Tahoe in a record-setting 10:34:48—the fastest time ever recorded for a woman and the second fastest time for an athlete of any sex. From the beginning of training to the weeks preceding the Lake Tahoe swim, RMR increased from 1382.9 kcal∙day-1 to 1720.6 kcal∙day-1. Exercise economy improved at low intensity workloads (28.0 ml∙kg-1∙min-1 to 25.8 ml∙kg-1∙min-1) but worsened at moderate intensity workloads (38.7 ml∙kg-1∙min-1to 40.8 ml∙kg-1∙min-1) with no change in V̇O2peak. Following the 10.5 h swim, body mass remained unchanged (59.9 kg), while grip strength declined (69.3 kg to 64.7 kg). Conclusions: This study provided new insights into the training regimen—and subsequent physiological adaptations—adopted by an elite female ultraendurance swimmer leading towards a record-breaking performance.