If you've just begun Zone 2 training, it's common for athletes to have trouble staying in Zone 2 without having to walk.
This is totally normal. Zone 2 training is challenging for most people when they begin, because slowing down to a walk to stay under a person's Zone 2 cap feels counter-intuitive -- they want to run, they don't want to walk.

But if you stick to it, you'll soon find that you don't have to walk as often -- and eventually you won't have to walk very much at all -- and in fact, you'll start going faster without your HR going up.

However, there may be times when you do have to walk again, and we'll get into that below.

If you're someone who's been successfully doing Zone 2 for a while, but suddenly your HR is spiking on you, here are a number of possible reasons this could be happening.

The body doesn't spike your HR for no reason at all -- there will be a reason, so make sure to be honest with yourself to find it.

Are you fueling properly before your workouts?

While you may see many Instagram fitness influencers preaching fasting, science has shown that performing endurance training on an empty stomach is a recipe for injury and burnout.

To make sure you're fueling properly, check the nutrition recommendations in every single MOTTIV workout we prescribe you on the app. (To confirm you're getting the correct recommendations, make sure you've put your correct body weight into your My Account settings.)

Also remember, race season is NOT the time to be cutting calories to lose weight. Your body needs all of the calories it can get to fuel your body while you're doing the hard pounding of endurance training. The off-season is a better time to cut calories for weight loss.

How is your sleep?

Athletes training for endurance sports absolutely need enough sleep if they want their bodies to keep up to their training without getting sick or injured. You should aim for AT LEAST 7 hours of sleep every night -- anything less and you're putting a tremendous amount of stress on your system, and it will be very hard for your body to recover from training for you to make progress.

There are lots of people who say to us, "Oh, I only NEED 5 hours a night." In reality, there are hardly any people who can truly get by on less than 7 hours a night -- science shows there are virtually no outliers in this area, meaning, even if you THINK you're getting by on 5 hours a night (or even less), you're actually doing damage under the hood that you can't yet perceive.

Your body can not properly recover from endurance training if you're not sleeping enough, and this will prevent you from getting faster and improving as much as your body is capable of.

Make sleep a priority, and your training will benefit.

How is your overall rest & recovery?

You can be getting 7+ hours of sleep per night but still not be doing enough for your body's rest and recovery.  If you have a busy job, a busy life, tons of family commitments, volunteer work, etc., and you're constantly busy outside of your training -- that is not going to allow your body to rest and recover the way it needs.

Prioritize some downtime, it's really important to allow your body the time it needs to rest and relax, because THAT is where you'll start to see endurance gains.

If you don't, you may find you aren't improving OR you're even regressing in your fitness.

Have you recently been sick or are you currently battling an illness?

Illness of any kind (cold, flu, stomach bug, virus, infection, etc.) can cause your heart rate to be elevated both during and after your illness.  So let's say you had influenza for a week, and now you're feeling better -- your HR may still be elevated while your body recovers.  Just because you feel better doesn't mean your body isn't still doing some repair-work that you can't feel.    

So what this means is, you still need to stay under your Z2 cap, and that can mean walking for a while as your body recovers, and you get back to your previous endurance and health.

Have the conditions changed?

The conditions you run in can absolutely cause your HR to spike.  

• Is the weather hotter or colder than usual?  
• Are you running in a different elevation or different conditions than usual?  (More hills or uneven ground conditions?)
• Are you suddenly going through a period of intense stress in your life?  (A sick parent or child, difficulty at work, difficulty in your relationship, etc.)

Any of these things can cause your HR to be higher than normal. All this means is that you may have to go back to walking until your body tells you it's time to run more.  Your HR NEVER lies.

Have you been following your workouts as prescribed?

If you've been doing more than your workouts tell you to do, you can get into an overtrained state -- and then your body will tell you to back off by raising your HR with minimal activity. Respect your body's signals and signs.

This could mean dropping a couple of workouts that week to give your body time to recover from whatever is going on. It could mean only doing parts of your workouts that week for the same reason.

Or, it can mean that you've committed to too many hours of training per week, and you may need to lower your weekly training hours for a period of time, to allow your body a bit more rest.