The higher the percentage of your maximum heart rate you are working at, the more intense it is. It’s intense work for your heart. It’s “in fashion” to train according to your heart rate and people zone in out being in the right zone for good and bad. You see, a strong, fit heart doesn’t speed up to maximum heart rate without really being pushed there. If you feel it’s easy being in your 90% zone, there are many likely reasons why:
1. You are not super fit yet. Your heart perceives your training intensity as really high and hence beats rapidly to provide the muscles with oxygen. It’s “spinning its wheels”.
2. You are overdoing stimulants like caffeine which raises your heart rate artificially and excessively.
3. Your individual maximum heart rate is higher (up to 20 beats higher I’ve read can be found in many people) so you are actually training at a lower intensity than you believe.
Training in the 90% of your max is a very intense zone. It’s not a ‘safe’ zone unless you are very fit and know your heart health. I for instance have a heart dysfunction, so I’ve gone through stress tests, ultrasound of the heart and EKG test just to make sure I’m playing it safe when I train at this level. When I train at 90% it is really hard. It’s hard to sustain the intensity and not see the heart rate drop. When I slow down if so just for a few seconds, my heart rate drops fast down. This is what it’s ‘supposed’ to be. Your heart has a built-in safety system. The higher you try to go, the harder you will need to work to get there.
Endurance athletes are training in this zone at a steady state to condition their bodies to use as much oxygen as possible. The 90% is where the lactic acid threshold usually is as well, and training at lactic acid threshold is grueling but very effective for achieving maximum cardio fitness. This level is extremely taxing for your body. Training in this zone is NOT something you do daily!
Gym rats who want to achieve a fit, muscular, lean look should not try to condition their bodies to an extreme endurance trained body. You see, that is not the muscle fiber type you’re going for. For us, intervals are better suited cause it trains the body more like weight training, it stimulates the fast twitch fibers that are stronger, more explosive and grow bigger.
I’ve had clients who were really overweight whose heart rate was up there at 85-90% when all they did was walking on a treadmill at 3 mph. Did it mean they were training efficiently? No. It meant they were so out of shape their heart rate rose up to the close maximum but the work output was very low. With weight loss and consistent training they’d be able to lower the heart rate while training at a way higher intensity level.
A strong heart and a strong body will be able to take many punches without being fatigued. If you can make it go up to maximum within minutes of steady state work without having to work really hard and see how it slowly increases to the high levels, then you should pace yourself and let your body gets conditioned bit by bit. Just like you wouldn’t try to squat 400 lbs as a beginner with lousy technique just because you CAN lift the weight using that lousy form, you should not go and train at an elite level cardio wise without training your body one progression at a time….