Like many people, I started running as a solo runner.  Every time I went for a run, I always ran at about the same pace. I never pushed myself to run harder. I was finally introduced to interval training when I joined my first run crew in 2017. Every week, our run crew did one Saturday long run and one Wednesday workout run.  Our Wednesday runs would consist of a 10-15 minute warm-up, a 20-30 minute workout of either hill repeats or speed intervals, and a 10-15 minute cool down.  These workouts were tough but doing them as a group somehow made them less painful.  When we started We Run North York, I wanted this tradition to continue so I asked a more experienced runner in the group to lead workout runs for us.  I’m so grateful that Matt Ma has been leading these weekly workouts for us ever since and he even shared weekly virtual workout runs throughout the pandemic lock-downs! 

If you’ve been running consistently (e.g. 3x/week) for at least a few months, and you’ve already started to build strides into the end of your easy runs, you can now start incorporating some short intervals into your training every other week.

What are intervals?

Intervals are a hard effort workout that involves a duration of running at a hard effort followed by recovery, repeated for a specific number of times. According to polarized training or 80/20 training, 80% of your training should be done at an easy effort and 20% of your training should be done at a hard effort. 

Benefits of intervals

• Improves your aerobic system: Interval training helps to improve your VO₂ max which is the maximum amount of oxygen your body is able to use during exercise. The greater your VO₂ max, the more oxygen your body can consume, and the more effectively your body can use that oxygen to generate the maximum amount of ATP energy. 
• Improves your anaerobic system: When you are doing high intensity interval training, your body is no longer able to use oxygen to convert fat and glucose into energy and switches to a process called glycolysis. This anaerobic process produces lactate which results in an increase in acidity in the muscle cells which slows down your muscle’s ability to produce energy to prevent more microdamage. By doing high intensity interval training, your body will be able to recycle lactate more effectively which means you’ll get tired less quickly.
• Improves your neuromuscular connection: Whenever you learn a new skill (e.g. riding a bike), you have to train your brain to communicate with your muscles to move in a new way. Similarly, when you run strides or intervals, you are teaching your brain to communicate with your muscles to run faster.
• Provides variety to your training: Since there are so many variables that can be changed for interval training depending on your current fitness level and what you are training toward, the possibilities are literally endless!

Four components of an interval workout

1. Run – Short intervals can range from 200-800m (or less than 3 minutes) and are good for shorter races (less than 10k) or those newer to interval training. Long intervals can range from 800m-2000m and are better suited for half/full marathon training.
2. Recovery – For short intervals, recovery can be greater than, less than, or equal to the duration of hard effort. If you are just starting to do internal training start with a 1:2 ratio of hard:recovery.  Long intervals typically have recovery of less than 3 minutes.
3. Rate of Perceived Effort (RPE) – Short intervals should be done at RPE 8-10 (hard) to mainly work your anaerobic system.  Long intervals should be done at RPE 7-8 (comfortably hard) to increase your lactate threshold. 
4. Repetitions – Beginners should target 20-25 minutes for an interval workout.  Experienced runners can increase to 40 minutes or more.  Remember to include 10-15 minutes of warm-up and cooldown before and after the workout.

Examples of intervals

Type	Run	Recovery	RPE	Repetition	Good for
Short intervals 1:2 ratio	200-400m	400-800m	9-10	4-6	Beginners
Short intervals 1:1 ratio	200-800m	200-800m	9-10	4-6	5-10k training
Short intervals 2:1 ratio	200-800m	100-400m	8-9	3-5	5-10k training
Long intervals	800-2,000m	up to 3 min	7-8	2-4	Half/Marathon training

By varying the 4 components of an interval workout, you will be able to increase the workload of your training and target different systems.  If you’ve never tried interval training before, be sure to progress gradually to avoid injury.  If you are doing 3-4 runs a week, intervals can be incorporated into your hard workout rotation along with other types of hard workouts like fartleks, hill repeats, or tempo runs. Remember to keep easy runs easy so you can do your hard days hard!