Swimming directly behind another swimmer, within about 50 cm of their toes, lowers drag and physiological cost and may leave you fresher for the bike; whether pool practice improves race drafting is untested
Interpretation
Consistent direction across small laboratory studies: in 11 swimmers at 95% of 1500 m pace, drafting at 0–150 cm lowered VO2, heart rate, lactate and RPE, with passive drag down 20–21% at 0–50 cm (Chatard and Wilson 2003); in 9 club triathletes (4 M, 5 F) drag fell 9% and VO2 11% behind an active lead, while swimming level alongside raised drag (Janssen 2009); in 8 well-trained male triathletes cycling efficiency was 4.8% higher after a drafted 750 m (Delextrat 2003); a review reports faster drafted 400 m swims (Brisswalter and Hausswirth 2008). The physiological benefit is graded moderate; the transfer of pool practice to open-water racing has no direct evidence and rests on general motor-learning principles (Schmidt and Bjork 1992).
Practical implication
Practise holding feet 0–50 cm behind a lane-mate, hip drafting slightly behind the lead swimmer's hands, sighting the swimmer ahead and changing feet in agreed pool sets over winter, then rehearse in open water in spring. Expect a smaller saving behind a kicking swimmer than towing studies suggest; the practice approach is inference.
Sources
5 sources, independently verified.
MSSE 35(7):1176–1181. 4-minute swims alone and drafting at 0, 50, 100 and 150 cm behind a lead swimmer: oxygen uptake, heart rate, lactate, RPE and stroke rate lower and stroke length longer in every drafting position. Passive drag fell 21% at 0 cm and 20% at 50 cm behind the toes; lateral drafting cut drag 6–7% at 50–100 cm behind the lead swimmer's hands. Best: 0–50 cm behind toes, or 50–100 cm behind hands at the side.
MSSE 41(4):837–843. Behind a passive lead swimmer drag fell 20% and oxygen uptake 25%; behind an actively swimming lead, drag fell 9% and oxygen uptake 11%. Directly alongside the lead, drag rose about 8–9% with small VO2 changes. Best position directly behind with about 0.5 m between lead's toes and drafter's hands. Participant details read in the full-text PDF; pressure mapping in one swimmer.
MSSE 35(9):1612–1619. Counterbalanced 750 m swims alone or drafting at the same pace, each followed by 15 min cycling at 75% of maximal aerobic power at free cadence: cycling efficiency 4.8% higher after the drafted swim (P<0.05), attributed partly to the lower relative swim intensity. Small, all-male, short ride.
IJSPP 3(1):3–15. Narrative review of drafting across sports. Swimming section summarises earlier studies, including drafted 400 m speed rising from 1.34 to 1.39 m/s (Chollet et al.) and the 4.8% cycling-efficiency gain after a drafted swim (Delextrat et al.). Read from a full-text copy; the 400 m figure is the review's report of a primary study not read directly.
Review of motor and verbal learning experiments: conditions that maximise performance during practice can be detrimental to long-term retention and transfer, while some conditions that slow acquisition (e.g. variation) can enhance it. Laboratory tasks, not swimming; no prescription for specific sports.