The MOVE by BJC Blog

Impact and Intensity

Friday, November 09, 2018

A few terms that are often heard in the fitness center are “high impact” or “low impact” and “high intensity” and “low intensity”. These concepts are not interchangeable, but both are t important components of a fitness program. Impact refers to the amount of force applied to the joints, ligaments, and tendons during exercise; thus high impact means that the joints, ligaments and tendons are being worked harder.  This may not always be a good thing, since joints and supporting tissues can be injured during repeated high impact activities.  Repair and recovery can also be costly, in both time and money. The term intensity is typically used to refer to a certain “level” of workload, i.e., monitoring heart rate during cardiovascular activity.

The intensity of cardiovascular exercise is related to heart rate .The more intense an exercise is, the more it raises your heart rate. The American College of Sports Medicine (ACSM) recommends that an individual exercise at an intensity that raises their heart rate to at least 60% of their maximum heart rate.  Your max heart rate can be calculated by taking 220 minus your age, i.e., if you are 35 years old, your estimated maximum heart rate would be 185 (220-35=185).  ACSM also states that it is safe to exercise at heart rates as high as 94% max.  An exercise is considered high intensity if you are exercising at a heart rate between 80-94% of your max. 

So what intensity should you be working at?  In order to provide the most benefit for your heart and lungs, 70-90% of your max heart rate is a good range, as it is challenging but not impossible to sustain for a short period of time. Lower intensity cardiovascular activity can provide many of the same benefits as high intensity activity, it just takes more of it to build a stronger heart and more efficient lungs.  Heart rate ranges of 50-70 percent heart rate max can provide benefit, and at these intensities, your body uses a higher percentage of stored fat as energy instead of readily available carbohydrates. This does not mean that to lose weight, you should do more low intensity cardiovascular activity; you should try to do both high and low intensity activities, because you will burn fat and benefit your heart and lungs. If you are unsure about what your intensity level should be, consult an exercise specialist at the WellAware Center to determine what type of program best suits you!

A low-impact activity simply means that at least one foot remains grounded during exercise.  Examples of low-impact activities are walking, step aerobics and roller blading.  At no point are both feet off the ground, so there is less impact on the joints and supporting tissues.  High impact activities are those where both feet leave the ground for a short period of time, i.e., running, jogging and jumping activities.  These activities have a greater effect on the joints, ligaments, tendons and muscles, and therefore require more energy also. There are also no-impact activities, such as elliptical machines, stair-steppers and swimming, where neither foot leaves the ground.  High impact activities typically burn more calories in a given period of time than their low impact counterparts.  Thus, you will burn the same (or more) calories by jogging slowly on a treadmill than you will moving quickly on an elliptical, due to the impact of the activity.  Unfortunately, high impact activities present possible joint problems in the ankle, knee, and hip.  Even in light running, gravity is trying to pull you down at a rate of 32 feet per second.  When running, the impact with the ground can be twice what it is when walking, since your feet are lifted higher off of the ground when running, and there is additional forward momentum.  Therefore, a 120 lb. person may be placing up to 240 pounds of pressure on the ankle, knee, and hip with each step.  Check with your doctor to decide whether low impact, high impact or no impact activities are best for you.

- Aaron Gutjahr, MSed, FMS, TPI CGFI/CGI, ACSM CPT

Manager, Move by BJC