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HEALTH & FITNESS:
Cardiovascular Endurance
by Dr. Brad Elliott
Endurance means different things to different athletes. Even among expert's definitions vary greatly. Funk and Wagnalls Dictionary defines endurance as "The capacity/or power to endure; ability to suffer pain, hardship or any other prolonged stress without succumbing; patient fortitude." (Ouch!)
Nutrition and fitness guru Dr. Phillip Maffatone considers endurance to be "a steady state level of activity where one can develop and sustain relatively high speeds at a submaximum effort over time; the ability to develop higher speeds while remaining predominately aerobic; increasing the percent fat burning and decreasing the dependence on carbohydrate utilization with training." The average triathlete or fly fisherman has this one memorized.
Dorland's Medical Dictionary, on the other hand, doesn't list the word endurance.
For the sake of this story, we will consider cardiovascular endurance to imply a level of aerobic fitness, which one pursues by sustained activity. "Distance sports" such as running, cycling, swimming, hiking, mountain biking, and cross-country skiing.
Aerobic activity means the body requires oxygen to generate energy ® in the mitochondria of the cell. Anaerobic activity (short, sprinting-type sports) implies the cell can provide energy without oxygen. In a one hour event only 2% of the cellular energy is derived from the bodies anaerobic system. Interesting to know for those hammering out speed workouts.
(Photo Caption)
Ivan Steber, an amputee triathlete from Upland, CA, registered an
impressive overall time of 12 hours and 36 minutes at the Ironman
USA Lake Placid on July 30th. He completed the 2.4-mile swim
in 1:08:02, 112-mile bike in 6:12:43, and 26.2-mile run in 4:55:28.
Photo
by Darryl Caron¾¾¾¾¾¾¾¾
For energy to be produced in the muscle cell, which ultimately equates to muscle contraction and a given action by a joint, that cell also needs either sugar (glucose) or fat.
For simplicity, let's say that aerobic activity will depend more on fat for energy production. Anaerobic activity (downhill skiing, running sprints, hockey) relies more on glucose (sugar).
One last physiology peril, the body not only has different muscle groups for different actions, but different fiber types exist within a given group.
Type I muscle fiber or slow twitch/red fiber is where fat is converted to energy. Gluconeogenesis is the term used to describe this action. This requires oxygen and a series of enzymes. There are a larger number of capillaries in these red fibers and they are responsible for maintaining submaximal efforts over time. You guessed it, endurance! An example is a 10K or marathon runner.
Type II muscle fiber or fast twitch/white fiber uses glucose for energy, without oxygen. It is not as highly vascular (blood-rich) and loves to fire at maximal effort and then shut down. Think of sprinter Michael Johnsonês hamstrings!
So, how do we determine our cardiovascular endurance? A number of methods exist. One way is step-up tests that utilize your pulse rate and a number of repetitions, as a workload is a good indicator. Measuring the individual's recovery response during this testing is also informative. Do you remember Presidential Fitness Testing day in gym class?
Another means of measuring cardiovascular endurance is using a treadmill or bicycle ergometer to measure the maximal rate at which oxygen can be utilized during exercise (Vo2 max). You can also determine your lactate threshold with such a study. I, however, have yet to find either of these readings on my bike computer!
According to sports medicine author Dr. Shephard Roy, the following may be a more practical means of determining your level of cardiovascular endurance.
From a sports-specific standpoint, you need to establish a baseline of distance and/or time. In doing so, the following variables need to be considered: intensity of training, duration of the workout, frequency at which the activity occurs.
Intensity can be determined by monitoring your pulse. Athletes of all levels should know your Training Heart Rate. It is generally accepted that your training heart rate can be calculated by subtracting your age from 220. This determines your maximum heart rate, your "redline," not to be exceeded.
If aerobic fitness is your goal, you should train at a sustained effort between 70-80% of your maximum heart rate. For example, a 35 year old female who wants to train at 80% would use the following equation: (220-35) x .80 = Training Heart Rate of 148 beats per minute. Using a heart rate monitor or simply checking your pulse against the clock will allow you to adequately monitor your intensity.
Duration is how long you need to sustain the Training Heart Rate. It is generally accepted that one must sustain or hold this intensity of exercise for 30 minutes or greater for fitness and endurance gains to be made. Yes, the longer the better, depending on your goals.
Frequency is the minimal number of workouts per week at your Training Heart Rate for a given duration. The minimal number workouts per week are two to improve your fitness, however it is recommended that most athletes strive for three or four workouts per week to build your endurance.
Please remember that exercise is stressing your body from a physiologic standpoint, so adequate rest is also important for muscle recovery and injury prevention. Pick an activity you enjoy the most, do it frequently, and listen to your body ® with a smile on your face!
Dr.
Brad Elliott is a certified Chiropractic sports practitioner in Clifton
Park. He enjoys working with athletes of all levels on a daily basis.
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