During gait, humans choose a combination of step length and step rate that minimizes V˙O2. However, little work has been reported on the existence of such optimization in swimming.
Purpose: The purpose of this study was to examine the manipulation of stroke rate on V˙O2 in submaximal, constant speed freestyle swimming.
Methods: Preferred stroke rate for swimming freestyle at 1.0 m·s−1 in a flume was determined for 10 competitive swimmers (mean ± SD: age = 33.3 ± 13.6 yr, height = 175.3 ± 8.6 cm, weight = 74.9 ± 12.2 kg). Participants then completed flume swims at 1.0 m·s−1 with stroke rates equal to −20%, −10%, 0%, +10%, and +20% of their preferred stroke rate in a randomized order during which V˙O2 was continuously monitored. Each trial continued for 1 min after steady-state V˙O2 was verified (∼4-5 min). During the final minute of each trial, V˙O2 was measured using the Douglas bag technique, HR was recorded, and kick rate (KR) was computed using the time needed to complete 30 kicks. RPE was reported immediately after each trial.
Results: V˙O2 increased 11%-16% (P < 0.05) when stroke rate was reduced but was nominally affected when stroke rate was increased. Likewise, HR increased 4%-6% (P < 0.05), and RPE increased 15%-30% (P < 0.05) when stroke rate was reduced but not affected when stroke rate was increased.
Conclusions: These data suggest that these swimmers preferred to swim freestyle at the lowest stroke rate (or the longest stroke length) that did not require an increase in V˙O2.