Learning to Draft in the Pool: Practising Feet-Swimming Over Winter

In a non-drafting triathlon, the swim is the one place where sitting behind someone is both legal and useful. Most age-groupers know this in theory. In practice, many spend the swim alone, either because they lose the feet in the first few hundred metres or because they've never practised holding them.

Winter is a good time to change that. Pools are where most triathletes swim from October to April, and a pool lane is an ideal place to learn the basic skills of drafting. This article covers what the drafting research shows, where the best position is, what it does for the bike, and how to practise it in the pool. The honest limit is that no study has tested whether pool drafting practice transfers to open-water racing, so the practice section is labelled inference.

TriForward's "Out of the Water With the Right Group" covers why swim position matters for the bike in non-drafting races. This piece is about the skill itself.

What drafting does

Less drag, lower effort

The best-known swim drafting study is a 2003 study by Chatard and Wilson in Medicine and Science in Sports and Exercise. 11 swimmers swam for 4 minutes at 95% of their best 1,500 m pace, once alone and then drafting at four distances behind another swimmer: 0, 50, 100 and 150 cm.

• In every drafting position, oxygen uptake, heart rate, blood lactate, perceived effort and stroke rate were significantly lower than when swimming alone, and stroke length was longer.
• Passive drag, measured by towing swimmers, fell by 21% with no gap behind the lead swimmer's toes and by 20% at 50 cm.
• Lateral drafting, at the lead swimmer's side, cut passive drag by 6 to 7% at 50 to 100 cm behind their hands.

The authors concluded that 0 to 50 cm behind the toes was the best position, and that at the side, 50 to 100 cm behind the hands was best. The abstract doesn't report the swimmers' sex or level.

What happens behind a real swimmer

Passive drag is measured by towing a swimmer who isn't swimming. In a race, the swimmer in front is kicking, which changes the water you're swimming through. A 2009 study by Janssen, Wilson and Toussaint in Medicine and Science in Sports and Exercise tested this in a swimming flume at 1.2 m/s, with 9 local triathletes (4 men, 5 women) aged about 20 to 51.

• Behind a passive lead swimmer, drag fell by 20% and oxygen uptake by 25%.
• Behind an actively swimming lead, drag fell by 9% and oxygen uptake by 11%.
• Directly alongside the lead swimmer, drag increased by about 8 to 9%, with only small changes in oxygen uptake.
• The best position was directly behind, with about 0.5 m between the lead swimmer's toes and the drafter's hands.

This study is especially relevant because the participants were ordinary club triathletes, and more than half were women. It also gives a more realistic picture: the drafting benefit behind an active swimmer is real but roughly half the size of the towing figures.

The two studies differ on the side position. Chatard and Wilson found a small benefit 50 to 100 cm behind the lead swimmer's hands, while Janssen and colleagues found a cost directly alongside. Inference: the side position only helps if you're slightly behind, roughly at the lead swimmer's hip or thigh. Level with their shoulders, you may be swimming into their bow wave.

Faster swimming at the same effort

A 2008 review by Brisswalter and Hausswirth in the International Journal of Sports Physiology and Performance summarised the earlier drafting research across sports. In the swimming section, it reported a study in which drafting during a 400 m swim raised speed from 1.34 to 1.39 m/s. That figure comes from the review's summary of the primary study, which TriForward couldn't access directly.

Inference: lower effort at the same pace means you can either swim the same speed more cheaply or swim faster at the same effort. In a race, the first usually matters more.

What it does for the bike

The question for triathletes is whether the saving in the water carries over. A 2003 study by Delextrat and colleagues in Medicine and Science in Sports and Exercise tested this with 8 well-trained male triathletes in wetsuits.

• They swam 750 m at competition pace twice, once alone and once drafting, in random order.
• Each swim was followed by 15 minutes of cycling at 75% of maximal aerobic power at a freely chosen cadence.
• Cycling efficiency was 4.8% higher after the drafted swim than after swimming alone.

The authors linked the improvement to the lower relative intensity of the drafted swim. It's one small study in men, with a short ride, and it measured efficiency rather than race time. But it supports the idea that drafting saves energy you can use later.

Why drafting needs practice

Drafting sounds simple: find some feet and follow them. In practice it's a skill with several parts:

• Holding position. Staying within about 50 cm of someone's toes requires constant small adjustments. Drift back a metre and much of the benefit goes.
• Sighting differently. In open water, you sight the swimmer ahead (bubbles, feet, the colour of their cap or wetsuit) as well as the buoys.
• Judging the feet. Feet that are too slow cost you time, and feet that are too fast will push you into an effort you can't hold.
• Comfort with contact. Touching toes, being touched and swimming in turbulent water are unsettling if you've never practised them.
• Moving between positions. Switching from feet to hip, or to new feet when a group splits, takes practice.

None of these skills is well studied. But motor-learning research suggests that practising a skill in varied, realistic conditions improves how well it's retained. A 1992 review by Schmidt and Bjork in Psychological Science argued that conditions which make practice harder, such as variation, can slow progress in the session but strengthen what's retained and transferred. Inference: drafting practised a few times in varied situations is more likely to be available on race day than drafting never practised at all.

Practising in the pool

The following sessions combine the studies above with common coaching practice. They're inference for triathletes, not a tested programme. Agree them with your lane-mates or coach first.

Basic feet-swimming

1. Pairs at matched pace. One swimmer leads and the other follows as closely as possible without touching more than occasionally. Swap every 100 or 200 m.
2. Distance awareness. Practise finding the 0 to 50 cm zone. If you touch the feet often, you're too close; if you can't see the bubbles clearly, you're too far back.
3. Notice the difference. Swim 200 m alone and 200 m on feet at the same pace, and compare how it feels. The studies above suggest the drafted repeat should feel noticeably easier.

Hip drafting

1. Side-by-side in a wide lane or at an empty end. The drafter sits at the lead swimmer's hip, slightly behind their hands, roughly where the Chatard study found a small benefit.
2. Breathe towards the lead swimmer to keep them in view, as you might in open water.
3. Avoid swimming level with their shoulders, where the Janssen study found higher drag.

Sighting and changing feet

1. Sight the swimmer ahead. Every few strokes, lift your eyes slightly to check the feet without lifting your head too much.
2. Feet switches. In a lane of three or four, the last swimmer accelerates to move onto new feet, then settles.
3. Fast starts onto feet. Short, hard efforts of 25 to 50 m to get onto someone's feet, then settle into your race pace behind them. This mimics the scramble after a race start.

Getting used to contact

1. Three abreast in a wide lane for a length at easy pace, if the pool allows and swimmers agree.
2. Swimming through turbulence behind a group of kickers.
3. Mass starts from the wall for a few strokes, with permission and in a quiet session.

In spring, take the same drills into open water, ideally with a coached group. That's where wetsuits, sighting buoys and waves add the parts of the skill the pool can't.

Choosing whose feet to follow

The studies above all matched the drafter to a lead swimmer of suitable speed. In a race, nobody does that for you, so choosing feet is part of the skill. The suggestions below are inference and coaching convention, not research findings.

• Know your own pace. A recent critical swim speed or 400 m test, as covered in TriForward's "Critical Swim Speed", tells you roughly what pace you can hold. Feet that are much faster than that will cost you later, even with the drafting saving.
• Use the pool to calibrate. Drafting sets with lane-mates of different speeds show you how much faster than your own pace you can follow comfortably. The Chatard study found lower effort at 95% of 1,500 m pace, but it didn't test how far above your own pace drafting lets you go.
• Look for a steady swimmer. Feet that surge and slow, or zigzag between buoys, waste the benefit. In pool sets, notice which lane-mates swim steadily and straight.
• Have a plan B. If you lose the feet, settle into your own pace rather than sprinting to chase. Practise this in the pool by letting the lead swimmer go after a hard start and holding your own pace for the rest of the repeat.

A triathlon scenario

The following example is illustrative, not drawn from a study. A 39-year-old triathlete swims 1,500 m in about 27 minutes and usually exits the water alone, a minute or two behind a group she could have stayed with.

• December to February: once a week, her club swim includes a 15-minute drafting set in pairs, swapping lead and follower every 100 m, plus some hip drafting at an empty end of the pool.
• March: the set adds feet switches and fast starts onto feet in a lane of four.
• April and May: open-water sessions with her club add sighting the swimmer ahead and finding feet after a beach start.
• Race day: she starts at the side of the group of swimmers at her pace, finds feet within the first 200 m, and swims at their hip when the group bunches at a buoy.

Inference: she may save effort in the water and arrive on the bike fresher. The research suggests the saving is real but modest, and depends on finding feet that are the right speed.

Common mistakes

• Following feet that are too fast. Drafting lowers effort, but not enough to make a much faster swimmer's pace sustainable.
• Following feet that are too slow. A comfortable ride behind someone slower costs time. Sight ahead and move up if needed.
• Sitting too far back. A metre or more behind, much of the benefit disappears.
• Swimming level with someone. The side position helps only when you're slightly behind.
• Not sighting for yourself. The swimmer ahead may be off course. Check the buoys as well as the feet.
• Never practising contact. The first time you swim in a crowd shouldn't be the race start.
• Ignoring lane etiquette. Drafting practice needs agreement. Constant toe-touching in a public lane makes you unpopular.

Does this work for slower swimmers?

The Janssen study used local triathletes, including more women than men, swimming at 1.2 m/s. Inference: that's about 1:23 per 100 m, faster than many age-groupers swim. Drag rises steeply with speed, so the absolute saving from drafting is likely to be smaller at slower speeds, but the relative saving may still be useful. Inference: for a slower swimmer, the bigger benefit of drafting may be pacing and confidence, having someone to follow, rather than the drag saving itself. TriForward's "Fixing the Weak Leg" covers whether a broader winter swim focus is worthwhile.

What we don't know

• Whether pool drafting practice transfers to open-water racing. No study has tested it.
• How much drafting saves in a real race, with waves, sighting and bunching, rather than in a flume or pool lane.
• How the benefit changes at slower speeds typical of many age-groupers.
• Whether the bike benefit holds over longer races and for women. The only study used 8 men and a 15-minute ride.
• The best way to teach drafting. The practice suggestions here are coaching convention and inference.

References

• Chatard JC, Wilson B. Drafting distance in swimming. Medicine and Science in Sports and Exercise, 2003;35(7):1176–1181. doi:10.1249/01.MSS.0000074564.06106.1F
• Janssen M, Wilson BD, Toussaint HM. Effects of drafting on hydrodynamic and metabolic responses in front crawl swimming. Medicine and Science in Sports and Exercise, 2009;41(4):837–843. doi:10.1249/MSS.0b013e31818f2a9b
• Delextrat A, Tricot V, Bernard T, Vercruyssen F, Hausswirth C, Brisswalter J. Drafting during swimming improves efficiency during subsequent cycling. Medicine and Science in Sports and Exercise, 2003;35(9):1612–1619. doi:10.1249/01.MSS.0000084422.49491.2C
• Brisswalter J, Hausswirth C. Consequences of drafting on human locomotion: benefits on sports performance. International Journal of Sports Physiology and Performance, 2008;3(1):3–15. doi:10.1123/ijspp.3.1.3
• Schmidt RA, Bjork RA. New conceptualizations of practice: common principles in three paradigms suggest new concepts for training. Psychological Science, 1992;3(4):207–218. doi:10.1111/j.1467-9280.1992.tb00029.x