How to Improve Cardiovascular Endurance for Sports

Endurance is a term widely used in sports and can mean many different things to different people. In sports, it refers to an athlete's ability to sustain prolonged exercise for minutes, hours, or even days. Endurance requires the circulatory and respiratory systems to supply energy to the working muscles in order to support sustained physical activity.

When most people talk about endurance, they are referring to aerobic endurance, which is often equated with cardiovascular fitness. Aerobic means "with oxygen" and during aerobic exercise, the body uses oxygen to help supply the energy needed for exercise. The objective of endurance training is to develop the energy production systems to meet the demands of activity for as long as they are required.

The body converts food to fuel via different energy pathways. In the simplest terms, the body can convert nutrients to energy with the presence of oxygen (aerobic metabolism) or without oxygen (anaerobic metabolism). These two basic pathways can also be further divided. The three energy systems most commonly mentioned in exercises include:

• ATP-CP (anaerobic) energy pathway: Supplies short bursts of energy lasting up to 10 seconds.
• Anaerobic metabolism (glycolysis): Supplies energy for short, high-intensity bursts of activity lasting several minutes.
• Aerobic metabolism: Supplies most of the energy needed for long-duration, less intense exercise, and requires plenty of oxygen. Waste products (carbon dioxide and water) are removed in sweat and exhalation.

Aerobic Metabolism and Endurance

Most often, a combination of energy systems supplies the fuel needed for exercise, with the intensity and duration of the exercise determining which method gets used when. However, aerobic metabolism fuels most of the energy needed for long-duration or endurance exercises.

Athletes continually strive to push their capacity to exercise harder and longer and increase their endurance. The factors that limit sustained high-intensity efforts include fatigue and exhaustion. Sports training has been shown to modify and postpone the point at which this fatigue occurs.

VO2 Max and Aerobic Endurance

VO2 max, or maximal oxygen uptake, is one factor that can determine an athlete's capacity to perform sustained exercise. It is linked to aerobic endurance.

VO2 max refers to the maximum amount of oxygen that an individual can utilize during maximal or exhaustive exercise. It is measured as milliliters of oxygen used in 1 minute per kilogram of body weight and is generally considered the best indicator of cardiorespiratory endurance and aerobic fitness.

Elite endurance athletes typically have a high VO2 max. Some studies suggest this is largely due to genetics. However, training has been shown to increase VO2 max by up to 20%. A major goal of most endurance training programs is to increase this number.

Muscle Fiber Type 

High-level endurance athletes often have a higher proportion of slow-twitch (Type I) muscle fibers. These slow-twitch fibers are more efficient at using oxygen (and aerobic metabolism) to generate more fuel (ATP) for continuous, extended muscle contractions over a long time.

They fire more slowly than fast-twitch fibers and can go for a long time before they fatigue. Therefore, slow-twitch fibers are great at helping athletes run marathons and bicycle for hours.

Endurance Training

With endurance training, the body becomes better able to produce ATP through aerobic metabolism. The cardiorespiratory system and aerobic energy systems become more efficient at delivering oxygen to the working muscles and converting carbohydrates and fat to energy.

There are many ways to train for improved aerobic endurance. The duration, frequency, and intensity of each type of training vary. Focusing on slightly different energy systems and skills will result in a well-rounded program that promotes a variety of physical adaptations.

Running or cycling, for example, increase heart and lung capacity, while resistance exercises build physical strength. Combining different types of workouts in your training program can help you to maximize your endurance. Some of the most well-known endurance training programs include:

• Long, slow distance training is the most common type of endurance training and the foundation for marathon runners, long-distance cyclists, and other athletes that need long, sustained steady energy outputs. It is also the easiest form of endurance training for new or novice exercisers.
• Pace/tempo training consists of training at a steady, but fairly high intensity; just slightly higher than "race pace" for a shorter duration (usually 20 to 30 minutes at a steady pace).
• Interval training consists of short, repeated, but intense physical efforts (usually 3 to 5 minutes followed by short rest periods). Interval training is a great opportunity to mix in resistance activities, such as calisthenics, along with short bursts of cardio. Battle ropes, for example, are a great way to improve cardiovascular fitness and endurance.
• Circuit training consists of a series of specific exercises performed for a short duration and rotated through in quick in succession with little or no rest in between. Traditional circuit training routines include both strength training, such as resistance bands, and endurance exercise, like using a cordless jump rope, and can be customized to meet any athlete's training goals.
• Fartlek training combines some or all of the other training methods during a long, moderate training session, such as working out on a vertical climber. During the workout the athlete adds short bursts of higher intensity work with no set plan; it's up to how the athlete feels.
• Strength training sessions performed once a week can help to improve your endurance. Aim to include 30 to 40 minutes of resistance exercises each week.