Effect Of The Swimmer'S Head Position On Passive Drag
Authors: Matteo Cortesi, Giorgio Gatta
DOI / Source: https://doi.org/10.1515/hukin-2015-0106
Date: 2015
Reading level: Beginner
Why This Matters for Freedivers
Freedivers spend a lot of time gliding (after push-offs, after turns in pool training, during duck dives and descents), and small drag reductions add up fast — less drag means less effort and less oxygen use. The practical takeaway is simple and immediately testable: during glides, keep the head neutral/aligned (not looking forward), because “head-up” can cost you around ~10% more resistance when you’re otherwise streamlined.
Synopsis
If you’ve ever done a long underwater glide and felt it “stall” early, there’s a good chance your body position — especially your head — was acting like a tiny brake. This study tested a simple question with real measurements: does head position change how much resistance (drag) you experience during a passive underwater glide? Ten experienced competitive swimmers were towed underwater at a steady depth (~60 cm) and at three fast speeds (1.5, 1.7, 1.9 m/s). They repeated the towing in two body setups: a streamlined position with arms extended overhead, and a less streamlined position with arms along the sides. For each, they tested three head positions: head-up (looking forward), head-middle (neutral/aligned), and head-down (looking more back/down). 
The results were very consistent: head-up created more drag. When swimmers were properly streamlined (arms overhead), simply bringing the head into a neutral/aligned position or slightly down reduced passive drag by about 10% compared with head-up. In the arms-along-the-sides position, head adjustments still helped, but the benefit was smaller (around 4–5%), because that body position already creates more resistance overall. The study also confirmed the obvious-but-important point: body position matters even more than head position — the streamlined arms-overhead posture reduced drag substantially compared with arms by the sides. The authors explain the “why” in plain hydrodynamics terms: the head is the first big shape the water hits, and lifting it disrupts smooth flow, increasing pressure resistance.
Abstract
The aim of this study was to investigate the effect of the head position on passive drag with a towing-line experiment in a swimming pool. The tests were performed on ten male swimmers with regional level swimming skills and at least 10 years of competitive swimming experience. They were towed underwater (at a depth of 60 cm) at three speeds (1.5, 1.7 and 1.9 m/s) and in two body positions (arms above the swimmer’s head and arms alongside the body). These two body positions were repeated while the swimmer’s head was positioned in three different ways: head-up, head-middle and head-down in relation to the body’s horizontal alignment. The results showed a reduction of 4-5.2% in the average passive drag at all speeds when the head was down or aligned to the swimmer’s arms alongside the body, in comparison to the head-up position. A major significant decrease of 10.4-10.9% (p < 0.05) was shown when the head was down or aligned at the swimmer’s arms above the swimmer’s head. The passive drag tended to decrease significantly by a mean of 17.6% (p < 0.001) for all speeds examined with the arms alongside the body position rather than with the arms above the head position. The swimmer's head location may play an important role in reducing hydrodynamic resistance during passive underwater gliding.