Charlotte Purdue is the third-fastest British female marathoner of all time, having covered the 26.2-mile distance in 2:22:17. To put that time into perspective, that’s like running eight parkruns in 16:51, back-to-back – and then sprinting another 2.2km. Speed and endurance like Purdue’s aren’t honed through one session, of course, but the ‘ins and outs’ workout is a staple of hers for a reason. Below, we’ve detailed how to use the session yourself, with some adaptions should you need them.
The Benefits
This session can be very effective at teaching your body to buffer lactate and represents a realistic feel of racing, where paces often vary a bit from mile to mile. Training in this way can help to build some ‘headroom’ above your goal race pace, making it feel easier.
The Session
Complete 20 x 1km with alternating ‘on’ and ‘off’ efforts. For Purdue, the ‘on’ efforts are run at a pace of 3:10 min/km and the ‘off’ efforts a little slower than marathon pace at 3:40 min/km.
For you, calculate your own target marathon pace and run the ‘on’ efforts a little inside it and the ‘off’ efforts a little outside it.
Adaptations for Other Runners and Races
No doubt about it, 20 x 1km is a seriously tough session. If you’re new to running or at the slower end of things, you’re going to want to adapt it. Cut the session back and run to time with something like 60 to 90 minutes total, with 45 minutes of that run as 3 minutes ‘on’ and 3 minutes ‘off’. Run to perceived effort and keep the focus on maintaining a steady ‘off’ pace just as much as worrying about how fast you go for the ‘on’ efforts.
If you're not running the marathon distance, but you have a half marathon coming, you could adapt the session to be 10 x 1k and then use your target half marathon pace; run the ‘on’ efforts a little inside it and the ‘off’ efforts a little outside it.
Give it a try.
Rick Pearson is the senior editor at Runner’s World UK. He’s been with the brand since 2017 and loves testing PB-friendly shoes for on and off road. Rick is a sub-three marathoner, 4-something miler and once completed 100 miles in less than 24 hours. He occasionally likes to remind people of these feats on the Runner’s World podcast, which he co-hosts.
Rick’s running CV also includes racing a steam train over 14 miles (he won, narrowly) and a horse over a marathon (he lost, comfortably).
Tom Craggs is Runner’s World’s Head Coach. He’s also the World Class Programme Endurance Performance Lead with UK Athletics. As a coach and PT with more than 10 years’ experience, Tom has worked with beginners to elites, including Team GB distance runners and Paralympic medallists. In addition to his athletics coaching qualifications, Tom holds an MSc in Performance and Coaching and Reps Level 3 Advance PT qualification. He’s passionate about helping runners of all abilities to get the very best from themselves.
