Exercise Heart Rate Question

[WolfpupNX]

Hi there.  I'm 34, a few extra pounds, and I've really been working out to improve my health and hopefully lose some weight.  I'm using primarily an incline trainer (treadmill with higher incline capability) and had a question about heart rate.

I know the most common formula for max heart rate (MHR) is 220-34(age)=186 bpm.  I try to target my HR between 93 (50% max) and 158 (85% max).  However, I'm working with incline trainer programs to build endurance, and at this point they sometimes briefly cause me to exceed the 158 number and approach 186 (100% of max).  Generally these are ~30 minute programs with less than a third of it above 85% and only a few minutes near the actual MHR.

My primary question is:
- How dangerous is it to hit MHR if you feel fine?  Obviously I'm tired when the workouts get intense, but normal tired, and I feel like I want to keep progressing to more difficult workouts, but given my dad died of heart attack early, I want to be sure I'm safe.  I'd been making things easier when I'm within 10 beats of MHR, but I feel like I could keep going.  I suspect, since MHR varies, mine might actually be higher than the estimates, but it's hard to say.  As long as I don't go over MHR for long, is it safe to approach/hit it?  Or should I stick to the 50-85% of MHR?

Thanks!

[WolfpupNX]

Thanks gymdandee for all the fantastic information!  Very helpful!

[gymdandee]

The risk of musculoskeletal injury increases with the amount of intense physical activity. People who are normally inactive should start slow and gradually increase the intensity and duration of their participation in sports.
It increases your risk of injury during exercise and suppress your immune system. Exercise becomes excessive when the intensity, duration or frequency of your workouts interfere with adequate rest and recovery between workouts. Your fitness level dictates how much exercise is too much.
Over-training influences hormone secretion. Endurance athletes, who often perform hours of cardio each day, can experience increased secretion of cortisol -- a hormone associated with stress and weight gain. Additionally, over-training can suppress your appetite by increasing the secretion of two hormones known as epinephrine and norepinephrine. Inadequate caloric intake during difficult training programs can reduce your recovery rate and intensify over-training symptoms.
Too much exercise can suppress your immune system. As your body struggles with fatigue and inadequate muscle recovery, energy reserved for proper immune-system function redirects to repair overworked muscles and bones. Reoccurring illness during a workout program indicates a lack of rest and possible over-training. Additionally, training while sick can lengthen your recovery time and hinder your training to a greater extent than taking a few days off from exercise.
An elevated resting heart rate indicates over-training. For example, sustaining a resting heart rate of 80 beats per minute when your usual resting heart rate equals 65 beats per minute represents an elevated resting heart rate. In addition, exercising too much can increase the time it takes for your heart rate to return to a resting rate after a bout of exercise. Therefore, you should record your resting heart rate throughout your program and take notice if your resting heart rate increases over time.

Your musculoskeletal system comprises muscle and bone. Muscles and bones experience microscopic damage during exercise and require 24 to 48 hours of rest between workouts for adequate recovery. Frequently forgoing adequate rest periods reduces your strength and causes previously easy exercises to become difficult. Attempting exercise in a weakened state can lead to sprains or muscle tears.

Your likelihood of developing over-training symptoms depends on your exercise program and fitness level. Elite athletes who follow proper rest protocols can perform two workouts per day without negative results. On the other hand, an exercise beginner may show signs of burnout after training once a day for an entire month. You should begin a workout program with one or two weekly sessions and increase frequency as you become accustomed to regular exercise. Consult a doctor if you feel you are experiencing symptoms of over-training.

Source: Melissa Ross  American Council on Exercise

[WolfpupNX]

Thanks gymdandee!

I'm curious now - how does an increase in heart rate increase risk of musculoskeleton injury?  I've read this before, but never quite understood the why behind it.

Will do re the doctor - thanks much!  I think I did overtrain once (but I was doing it every day...something I don't do anymore and make sure I have break days).  

Really appreciate all your help!

[gymdandee]

It’s not a good idea because you're likely to suffer sore joints and muscles if you do. It raises your risk for a muscle skeletal injury. Above 85 percent of your maximum heart rate also puts you at risk for over training. When you over train, your body get weaker instead of stronger, which leads to increased fatigue and decreased performance. You also are more prone to injury.
Talk to your doctor and get his/her opinion!!

[WolfpupNX]

Hi gymdandee, and thanks so much for the DETAILED reply!

Yes, I am cleared to exercise by my doctor!  No big medical conditions - I was getting borderline high with blood pressure, but have managed to get that down with some lifestyle changes (including exercise) and supplements to a very healthy level.  Also, I've actually been exercising regularly for some time (over a year regularly, and was on and off before that) - it's just I've increased the intensity a bit lately.  

Sprint 8 looks interesting.  My incline trainer doesn't support it natively, but the programs I'm doing aren't THAT different (they're Jillian Michaels designed workouts).  They definitely tend to have intervals tougher and then easier (with warmup and cooldown), but each one is different.  

Thanks for the alternative formulas as well!

I guess the main thing I'm confused on is, I've heard the going above 85% and poor heart rate recovery times before...but I'm unclear if that's a bad thing long-term, or if training at that intensity might eventually bring down heart rates.