While exercising for 80 minutes a week provides some benefits, the Physical Activity Guidelines for Americans recommends that adults exercise at a moderate intensity for least 150 to 300 minutes a week. Cycling on a stationary bike is considered a moderate-level aerobic exercise.
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To maintain a four-day-a-week schedule on an exercise bike, you should work out for 75 minutes each day.
Exercising for 20 minutes, 4 times a week, on the stationary bike is OK, but 75 minutes each time would be better — as would filling out the rest of your week with other 20-minute activities like brisk walking, strength training and flexibility movements.
Exercise Every Day
The average adult needs a certain amount of exercise each day. This amount is based on the intensity level of the activity. Aim for either 38 minutes of moderately intense cardio four days a week, or 25 minutes of vigorously intense cardio three days a week.
If you're pedaling at a higher intensity on a stationary bike, 20 minutes a day for four days a week may be enough exercise to meet the cardiovascular recommendation for physical activity.
Read more: How to Ride an Exercise Bike
Check Your Heart Rate
Gauging the intensity of your workout is as simple as checking your heart rate. For an activity like cycling on a stationary bike to be considered vigorous, your target heart rate typically must reach between 70 and 85 percent of your maximum heart rate.
Maximum heart rate is 220 beats per minute minus your age, so someone who is 45 years old has a maximum heart rate of approximately 175 beats per minute. In this situation, sustaining a heart rate of 122 to 149 beats per minute for four 20-minute sessions on a stationary bike meets your cardio needs for the week.
You Need Strength Training
Regarding the Physical Activity Guidelines for Americans, cardio is only a portion of the recommendation. You also need strength training each week, according to ACE Fitness. This parameter is set at eight to 10 weight-bearing activities, two times a week.
Each activity should consist of at least eight to 12 repetitions. Lifting weights, using resistance bands or taking part in a kettlebell workout twice a week can meet this recommendation.
Read more: Muscles Targeted With a Stationary Bike
If your goal for exercise is weight loss, four 20-minute sessions can help you shed pounds but not usually at the desired rate. If you weigh 155 pounds and cycle on a stationary bike at a vigorous level, you're likely burning about 13 calories per minute according to Harvard Health Publishing. After 20 minutes, you've racked up a total of 260 calories. Doing this four times a week equates to 1,040 calories.
For you to lose 1 pound of fat, you must generate a deficit of 3,500 calories, so you're looking at a pound of weight loss every three and a half weeks. By raising your activity level to the recommended 300 minutes a week, you can increase your weight loss to 1 to 2 pounds per week, depending on your current weight.
- American Heart Association: "Know Your Target Heart Rates for Exercise, Losing Weight and Health"
- Harvard Health Publishing: "Calories Burned in 30 Minutes for People of Three Different Weights"
- Health.gov: “Physical Activity Guidelines for Americans, 2nd Edition: Chapter 4. Active Adults”
- Harvard Health Publishing: "Pedal Your Way to Better Heart Health"
- ACE Fitness: "8 Ways Strength Training Creates Change in the Body"