Affects of swimming 1,500m upon cycling performance in triathlon.

How do you see Olympic triathlon? Do you see an endurance event lasting 2-3 hours in duration, or do you see a 1,500m swim, a 40k bike and a 10k run? Due to the nature of triathlon, it’s easy to view it as three separate disciplines, when in fact, it is one continuous event.

Does it sound feasible that your swim can affect subsequent cycling performance? After all, swimming does primarily use your arms. Delextrat et al (2005)* set out to determine if and by how much a 1,500m swim affected subsequent cycling performance. Their study involved athletes swimming a 1,500m time trial in the pool, before jumping onto cycle ergometers at poolside and riding for 30 minutes at 75% of maximal aerobic power (measured in watts). On a separate occasion, the athletes repeated the cycle phase, without having completed the swim. During the two cycle rides, oxygen consumption, heart rate and blood lactate levels were monitored and recorded.

Delextrat found that the 1,500m swim had a dramatic affect upon cycling. When compared against the “cycle only” trial, the athletes showed a 5% increase in oxygen consumption and 9.3% increase in heart rate at the 5 minute mark, but gradually these numbers reduced to match those of the cycle only trial. By contrast, lactate levels were a huge 56% higher at the 5 minute mark on the bike and were still 43.9% higher after 30 minutes of cycling. It appeared that lactate rose sharply due to the prior swimming and athletes failed to recover from that rise.

Clearly, such a large rise in lactate, which remained throughout the cycle test, would have a dramatic affect upon cycling performance. In addition to slowing the athletes, it would also result in faster glycogen depletion. The high lactate levels suggest a significant contribution from the anaerobic system.

Delextrat’s findings matched those of previous studies (Delextrat 2003 and Laursen 2000), which also suggested that swimming has a negative affect on cycling performance. While these earlier studies had involved 750m and 3,000m swims respectively, the aim of the 2005 study was specifically to examine the 1,500m distance. A pattern though appears to emerge from all three studies, indicating that the shorter and more intense the swim, the greater the effect upon lactate, HR, and oxygen consumption during the cycle section.

In practical terms, if you swim too hard, it will affect your cycling. We already accept that biking too hard affects running performance, so at least this completes the full set!

So, if you are a more efficient swimmer, there will be a positive knock on effect for your cycling and running performance. Maybe the athletes in the 2005 test were poor
Swimmers and that’s why the results were so significant? Unfortunately not – they were national standard athletes averaging 30km swimming per week. We can therefore presume that the impact of swim performance would be much greater for non-efficient swimmers. I’ll admit, that I have completed a swim/bike brick in my life but these results suggest that maybe it would be beneficial if you are focussing attention on sprint and Olympic distance triathlons.

Pacing plays a critical role. I’m sure everybody has been guilty of the mad sprint that occurs at the swim start, but going into oxygen deficit during the swim may be very hard to recover from during the cycle section. There’s a strong possibility that you may not recover.

In summary, if you are still viewing triathlon as three disciplines, you need to adjust your thinking. Each of the disciplines are greatly influenced by the others. The Olympic triathlon is a single endurance race.


* Delextrat et al. (2005). Does Swimming affect cycling energy expenditure in well trained triathletes. Journal of Applied Physiology. 30(4):392-403.


About the author of this training article
Marc Laithwaite, is Sports Science & Coaching Director, at The Endurance Coach. Mark has a Bsc (Hons) sports science and is working towards his Phd sports science. He is a member of the British Association of Sports and Exercise Scientists (BASES), a British Cycling Federation Blood Analyst, BTF Level 3 Coach & Coach Educator, UKA Level 3 Coach and ABCC Level 3 Coach.

The Endurance coach, provides sports science and coaching support services for endurance athletes. Their services include VO2 max testing, lactate profiling and metabolic assessment for endurance athletes of all standards in their own sports testing lab. The Endurance Coach also runs a range of training camps throughout the year and offers physiotherapy and rehabilitation services. For more information or if you are looking for world leading coaches to assist you, e-mail The Endurance Coach.

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