Mixed Intensity Intervals

Mix It Up! The Why and How of Mixed-Intensity Workouts

BY Matt Fitzgerald

Why every athlete should consider mixed-intensity workouts, and how to integrate them into your annual training plan for optimal success.

Most triathletes target a single intensity in almost all of their workouts. Maybe it’s a basic aerobic or endurance-building swim, ride, or run that is done at a slow and steady pace. Or maybe it’s a “tempo” session with one or two sustained efforts at lactate threshold intensity, sandwiched between a warm-up and a cool-down. Maybe it’s an interval session featuring a certain number of repetitions of uniform length or duration, all targeting the same high intensity. These are all effective workouts, but there is something to be said for the occasional workout including a range of different intensities.

Keep Things Interesting

First of all, mixed-intensity workouts are a literal change of pace, and as such, they’re an effective way to keep your training fun and interesting. These workouts are also a good way to get appropriate doses of different intensities. For example, if you’re at a point in your training where you can benefit from a little work at VO2max intensity—but only a little—why set aside an entire day for it when you can incorporate that work into a session focused on an intensity you need more of—say, lactate threshold?

Dial In Your Pacing

Yet another benefit of mixed-intensity workouts is that they help teach effective pacing. Can you shift accurately from Ironman 70.3 run pace to Olympic-distance run pace to sprint triathlon run pace—by feel? Most triathletes can’t. Incorporating mixed-intensity workouts into your training will help you correlate your subjective perception of effort with objective measures of intensity.

What does a Mixed-Intensity Workout Look Like?

A good example is what we call the Cycling Mixed Intervals (CMI) workout. Not for the faint of heart, CMI consists of a challenging mix of intervals in zones 3 and 4 (note that our 80/20 intensity zone scale is slightly different from TrainingPeaks’s default system).

The easiest version of the workout comprises two hours of total riding with 2 x 20 minutes in Zone 3 (91-100% FTP) and 10 x 1 minute in Zone 4 (102-110% FTP). The hardest version is padded with an extra 90 minutes of low-intensity riding. All versions of the CMI workout serve to increase lactate threshold and aerobic capacity. Half and full Ironman athletes may question the necessity of the suffering caused by this session, but the resulting raw increase in sustainable output will pay off in subsequent workouts and on race day.

While athletes training for longer triathlons need not incorporate CMI’s into their training beyond the midpoint of a training cycle, sprint and Olympic-distance racers should consider sprinkling them in. Just remember that pacing is critical in the first Zone 3 interval; start at the low end of the zone and work your way up.

Get the Specifics

My 80/20 Triathlon Plans, co-created by David Warden (available online through TrainingPeaks, and offline in our new book, 80/20 Triathlon), include a good selection of workouts to choose from, include running Mixed Intervals workouts with similar structure and benefits to the cycling version described above. But you don’t have to purchase one of these plans to make use these mixed-intensity workouts. If you own a Garmin device compatible with the .FIT format, you can download any of them on an à la carte basis from our free 80/20 Workout Library.

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The Ultimate Full-Distance Training Guide

Training Guide

This guide is designed to be used as you train for a full-distance triathlon, with in-depth information on every part of the process. Each chapter is packed with tips, workouts, and insights from triathlon coaches, to give you all the tools you need to succeed.

Trainingpeaks Author Matt Fitzgerald
About Matt Fitzgerald

Matt Fitzgerald is a journalist, author, coach and runner specializing in the topics of health, fitness, nutrition, and endurance sports training (read more about Matt on his blog). Matt uses TrainingPeaks to train, coach and deliver pre-built training plans for runners including training plans built specifically to be used with a Garmin Forerunner. View Matt’s 80/20 running plans here and his 80/20 triathlon plans here.

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