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Swim 2 Run

Speedo have been helping seasoned runners Kerry McCarthy and Sarah Curtis take their fitness to a whole new level while training for the London Marathon. Working with University of Portsmouth and Annie Emmerson (National Triathlon Champion), our runners have taken part in a unique research study which scientifically measures their fitness before and after taking our #Make1KWet challenge.

Watch the mini-series

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Ready for the #Make1KWet Challenge?

You're used to training for a 5K run or completing a 10k cycle, but is that really enough to push your fitness? What if you were to swap your 5K on the road or 10k on your bike for 1K in the water? Take part in the #Make1KWet Challenge by swimming for a kilometre, and test your results against your running routine!

Meet Kerry, Sarah & Annie

Find out more about Kerry and Sarah by checking out their biogs and the results from the research study and then follow their journey by watching the Eurosport mini series or follow us on Facebook,Twitter and Instagram.


Kerry McCarthy is the Commissioning Editor for Runner’s World UK. Based in South London, the 37 year old has been running for more than 13 years and completed 41 marathons and a total of over 300 races, including 12 marathons in 12 days for charity.

Kerry’s love for fitness spans far and wide; for him it’s a brilliant cure for clearing your head, improving mood, self-esteem and overall health.

Until recently, Kerry’s experience of swimming had been minimal. Before he started his Make 1K Wet training with Annie Emmerson, he could only swim 50m before having to stop and rest.

Kerry recognises swimming as an important life skill, and hopes to be able to develop his swim training further to enable him to venture outside his comfort zone and try a few triathlons.


29 year old Sarah Curtis is a fundraiser for charity Smile Train, and is studying Counselling and Psychotherapy at university in London. As a keen runner, Sarah is also a member of a number of British running collectives, including Run Dem Crew.

Since joining Run Dem Crew in 2016, Sarah has met many like-minded people which has helped her naturally integrate running as a huge part of my social life.

Running has helped Sarah to have a better relationship with her body, appreciating what it can help her achieve in races and events, but also to help her feel happier in herself. It helps to clear her head, solve problems, and have a more positive outlook on life.

Since Sarah has been running she has completed numerous 10Ks, three half marathons and three marathons, including the 2017 Tokyo marathon. Alongside running and swimming, Sarah is a keen yogi and takes a keen interest in the positive effects fitness and diet can have on mental health.

The Research Study

Fitness coach, Annie Emmerson joined forces with the University of Portsmouth to put swimming to the test. Annie has helped Sarah and Kerry, develop a swim and run plan for the London Marathon.

Working side by side with the University of Portsmouth tests where undertaken before and after their new training plan to discover if their time in the water makes a difference to their overall fitness. Here’s how the participants were measured:

Speed at lactate threshold (km/h) Running speed at the lactate threshold i.e. exercise intensity at which lactate begins to accumulate in the body. This measure is widely reported as being the best indicator of running fitness and the most reliable predictor of endurance performance.

PImax (cmH2O) Maximal inspiratory mouth pressure – measure of inspiratory muscle strength. Flexibility (cm) Sit and reach test – measure of hamstring and lower back flexibility.

VO2 max (ml/kg/min) Maximal oxygen consumption (measured relative to body mass) – measure of cardiorespiratory fitness & indicates the maximum capacity to utilise oxygen during exercise per minute.


Despite having dropped one run a week, Kerry's speed at lactate threshold has increased showing that his fitness and endurance are improving.

Measure Pre-Programme 8 Weeks Later
Speed at lactate threshold 12 14
PLmax 102 115
Flexibility 20 28
V02 max 43.22 47.75


Sarah's strong stats indicate that swimming has helped to make her more flexible and increase her aerobic capacity.

Measure Pre-Programme 8 Weeks Later
Speed at lactate threshold 12 14
PLmax 72 87
Flexibility 19 24
V02 max 48.81 46.74

Take our #Make1KWet challenge

Just like Kerry and Sarah. Click below to find out everything you need to know.