VO2 max

What is VO2 max

VO2 max is also called maximal oxygen uptake, is the highest amount of oxygen that your body can utilize during exhaustive aerobic exercise whilst breathing air at sea level 1). VO2 max is the amount of oxygen your heart can pump throughout your body and the highest rate of oxygen consumption during exercise done at maximal intensity 2). The V is for volume, the O for oxygen. VO2 max is one of the most commonly used indicators of aerobic power and metabolism 3) and is used regularly to measure aerobic performance, VO2 max is considered the gold standard and is the most important measure of aerobic ability. Exercise physiologists gauge fitness by looking at your VO2 max. Furthermore, VO2 max is an important independent prognostic marker in heart failure and is used as the indication criteria for cardiac transplantation 4). Several factors affect VO2 max value, factor such as age, gender, genetics, ethnicity, body composition, physical activity level, and exercise type 5).

VO2 max reflects your physical fitness. Maximal oxygen uptake as a measure of aerobic capacity has been determined as the international standard of physical activity 6). The basic unit of measuring the VO2 max (maximal oxygen uptake) is it’s absolute value expressed in liters or milliliters per minutes. However, the absolute value is highly affected by body weight; so VO2 max is often expressed as milliliter /kg body weight/minutes. The reduction in the physical activity affects body composition factors like body fat percentage, body mass index and body muscle mass. There are close relationships between the body composition factors and aerobic, cardiovascular fitness. With decrease in body fatness, there is increase in aerobic fitness 7). Recent studies suggest that even in young, physically, highly active men with an obviously optimal lifestyle; a lower BMI (body mass index) is associated with more risk profile for vascular disease. For young, active sports persons all these factors are concerned for their cardiovascular risk profile 8).

Cardiorespiratory fitness is defined as an integrated ability of cardiovascular and pulmonary systems to supply the oxygen demands of skeletal muscle during sustained physical activity 9). Over the past three decades, cardiorespiratory fitness has emerged as an important predictor of all-cause and cardiovascular mortality, independent of sex, age, ethnicity, adiposity, smoking status, alcohol consumption and other health conditions 10). Cardiorespiratory fitness is routinely expressed in VO2 max or maximal oxygen uptake. The VO2max concept represents the energy cost of physical activities as a multiple of the resting metabolic rate (3.5 ml O2/kg/min) and is mostly used to estimate the functional capacity in healthy people and patients with chronic disease 11).

Hill and colleagues 12), in the 1920s, conducted a series of experiments, using Douglas bags to collect expired air samples during maximal exercise, which leads to the ̇VO2 max concept. The authors defined ̇O2max as a plateau of oxygen uptake that cannot be increased, despite additional increases in exercise workload.6 Thus, ̇VO2 max represents the maximal integrated physiological capacity of the cardiovascular, respiratory and skeletal muscle systems, entitled the maximal aerobic capacity 13). Over the years, ̇VO2 max gained a strong clinical and scientific relevance. Evidence consistently demonstrated an inverse relation between VO2 max levels and quality of life, risk factors, chronic diseases and mortality 14).

The primary criterion for attainment of VO2 max is a plateau in VO2 15). Several secondary criteria exist in the case of a plateau in VO2 not being reached, which include a rise in respiratory exchange ratio above 1.15, blood lactate concentration above 8 mmol/L and increase in heart rate to age-predicted maximum 16).

Historically, the achievement of maximal oxygen uptake (VO2max) has been based on objective criteria such as a leveling off of oxygen uptake with an increase in work rate, high levels of lactic acid in the blood in the minutes following the exercise test, elevated respiratory exchange ratio, and achievement of some percentage of an age-adjusted estimate of maximal heart rate 17).

You can have your VO2 measured by an exercise physiologist or other fitness expert, who will perform a simple test to see how your heart rate responds as you add exercise intensity by working harder. You’ll come away with a target heart rate matched to your current fitness and a plan for how to keep improving.

You can also gauge your VO2 max yourself by looking at how easy or hard it is for you to perform common daily activities.

VO2 is measured as the uptake of milliliters of oxygen per kilogram of body weight per minute. Sitting at rest is equal to 3.5 milliliters of oxygen per kilogram of body weight per minute.

Check off the ones you can do with ease. Then focus on the one that would push your heart rate and breathing into a zone you’d describe as “very hard.” That’s the one closest to your present VO2 max.

For example:

Required VO2

  • Sitting (resting VO2): 3.5 mL of oxygen per kilogram of body weight per minute
  • Cooking dinner: 7 ml O2/kg/min
  • Brisk walking: 15 ml O2/kg/min
  • Climbing stairs: 22 ml O2/kg/min
  • Jogging (5 mph): 25 ml O2/kg/min
  • Running (8 mph): 41 ml O2/kg/min

VO2 max test

Accurately measuring VO2 max involves a physical effort sufficient in duration and intensity to fully tax the aerobic energy system. In general clinical and athletic testing, this usually involves a graded exercise test (either on a treadmill or on a cycle ergometer) in which exercise intensity is progressively increased while measuring:

  • ventilation and
  • oxygen and carbon dioxide concentration of the inhaled and exhaled air.

VO2 max is reached when oxygen consumption remains at a steady state despite an increase in workload.

VO2 max direct measurements

All participants performed a maximal exercise test using a Trackmaster treadmill. For the purpose of the study the treadmill was calibrated in order to ensure the accuracy of grade and speed. Subjects exercised to exhaustion using Bruce protocol. All athletes did not use the handrails. The electrocardiogram was monitored continuously during the test (CH-2000, Cambridge Heart Co., USA). The VO2 max was measured via an ergospirometric device based on breath-by-breath gas analyzing system (Ultima Series, MedGraphics, USA). Prior to testing, a pneumotachograph was calibrated using a 3.0 L-syringe at various flow rates. Thereafter, oxygen and carbon dioxide analyzers were calibrated with known gas mixture according to the specifications of the manufacturer. The following exercise test criteria were used for the achievement of VO2 max:

  1. Leveling off (plateau) of oxygen uptake with an increase of work rate.
  2. Respiratory exchange ratio (VCO2/VO2) greater than 1.10.
  3. Achievement of 90% of the age-adjusted estimate of maximal heart rate.

In addition, the following parameters were recorded from the cardiorespiratory exercise test: the duration of the test, the maximal value of VO2 max both by the ergospirometer and the exercise testing software unit using the Bruce protocol, the maximal pulmonary ventilation (VE max), the maximal heart rate (HRmax), and the respiratory exchange ratio (RER).

How to calculate VO2 max?

VO2 max can be calculated directly by the measurement of exhaled gases during cardiopulmonary exercise testing or can be estimated using equations. According to Bruce et al 18), in a prediction equation, VO2 max is dependent on pretest physical characteristics, such as gender, age, physical activity level, weight, and height. In turn, in an estimation equation, VO2 max is dependent on variables obtained during an exercise test (treadmill test), including speed, inclination, load, duration, and heart rate. For the prediction or estimation equation, it is important to understand the structural and local characteristics of the population for which the equation is created or validated; such equations are created with the goal of obtaining a VO2 max value closest to the actual oxygen consumption 19). The VO2 max values measured directly with cardiopulmonary exercise testing can be compared with the VO2 max values predicted for a particular age group 20). The two equations most often used in cardiopulmonary exercise testing softwares include the equation reported by Jones and Campbell 21), which has been modified for the treadmill, and the prediction algorithm of Wasserman et al 22). There is empirical evidence 23) that these equations overestimate the predicted VO2 max values when compared with direct measurements performed with cardiopulmonary exercise testing.

VO2 max indirect calculations

The Jones equation for the treadmill 24):

  • VO2 max predicted for male subjects = [60.0 – (0.55 × age)] × 1.11
  • VO2 max predicted for female subjects = [48.0 – (0.37 age)] × 1.11

The Fick equation

  • VO2 max = Q (cardiac output of the heart) X [CaO2 (arterial oxygen content) – CvO2 (venous oxygen content)].

(CaO2 – CvO2) is also known as the arteriovenous oxygen difference and these values are obtained during an exertion at a maximal effort.

Q (cardiac output of the heart) = heart rate × stroke volume

American College of Sports Medicine equation 25):

  • VO2 max (walking) = (0.2 x speed of treadmill) + (0.9 x speed x treadmill grade) + 3.5
  • VO2 max (cycling) = [(10.8 x watts) /weight in kg] + 7

Average VO2 max

The average untrained healthy male has a VO2 max of approximately 35–40 mL/kg/min 26). The average untrained healthy female has a VO2 max of approximately 27–31 mL/kg/min 27). These scores can improve with training and decrease with age, though the degree of trainability also varies very widely: conditioning may double VO2 max in some individuals, and will never improve it in others.

What is a good VO2 max?

In sports where endurance is an important component in performance, such as cycling, rowing, cross-country skiing, swimming and running, world-class athletes typically have high VO2 max. Elite male runners can consume up to 85 mL/kg/min, and female elite runners can consume about 77 mL/kg/min 28). Five time Tour de France winner Miguel Indurain is reported to have had a VO2 max of 88 mL/kg/min at his peak, while cross-country skier Bjørn Dæhlie measured at 96 mL/kg/min 29).

How to increase VO2 max

The factors affecting VO2 max are often divided into supply and demand 30). Supply is the transport of oxygen from the lungs to the mitochondria (including lung diffusion, stroke volume, blood volume, and capillary density of the skeletal muscle) while demand is the rate at which the mitochondria can reduce oxygen in the process of oxidative phosphorylation 31). Of these, the supply factor is often considered to be the limiting one 32). However, it has also been argued that while trained subjects probably are supply limited, untrained subjects can indeed have a demand limitation 33).

Factors that affect VO2 max are: age, sex, fitness and training, altitude, and action of the ventilatory muscles 34). VO2 max be a poor predictor of performance in runners due to variations in running economy and fatigue resistance during prolonged exercise 35).

Cardiac output, pulmonary diffusion capacity, oxygen carrying capacity, and the peripheral limitations of muscle diffusion capacity, mitochondrial enzymes, and capillary density are all examples of VO2 max determinants. The body works as a system. If one of these factor is sub-par, then the whole system loses its normal capacity to function properly 36).

You can strengthen your heart and lungs by adding distance, time or intensity when you exercise. And the most recent evidence shows that boosting intensity works more efficiently than increasing time or distance.

When you walk quicker, cycle harder or swim faster, it can also take less time to build heart and lung strength. That’s an extra perk for the time-crunched.

Even seasoned exercisers can boost their health benefits and improve VO2 max by increasing the duration or intensity of their workouts. Interval training is one way to increase intensity. High-intensity interval training alternates bursts of more-vigorous exercise with intervals of lower intensity exercise. You can modify the intensity and duration of each interval to suit your physical activity goals. In order to make progress, you need to spend as much time as possible at, or close to, your VO2 max.

Try these strategies to boost your cardiovascular fitness this week:

  1. Add distance, time or intensity to your walk, run or other workout once this week.
  2. Add physical activity to your calendar one extra day this week. Set a specific time for it.
  3. Partner up to exercise with a friend or loved one. Move fast enough that it’s not easy to talk.

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