You don't have to run marathons or spend half your life on the treadmill at the gym to have cardiorespiratory fitness. In this article we debunk the biggest myth in the history of health and nutrition!

Cardiorespiratory fitness is one of the most important factors that contribute to a person's overall health.

You have certainly heard that we need to exercise often and that we need to do aerobic exercise to maintain it in order to be healthy.

So let's see how valid are these claims? Get ready, because you will read things that others dare not confess to you.

HOW CARDIORESPIRATORY FITNESS IS MEASURED

There are two common ways of measuring cardiorespiratory fitness and therefore health: V̇O2peak and V̇O2max.

V̇O2max, or so-called "aerobic capacity", as aerobic metabolism must be employed for this measurement, is "the oxygen uptake during an exercise that is of such intensity that the actual oxygen uptake reaches a maximum beyond which the effort cannot be increased".

So we're talking about an oxygen uptake plateau, which is measured during a process called aerobic capacity assessment by ergometry and involves some gruelling, progressively increasing aerobic tests.

V̇O2peak, on the other hand, is the highest value of oxygen uptake achieved on a particular test, designed to bring the subject to their limit, regardless of the subject's effort.

In short, testing for V̇O2peak is easier for the average person, since they don't have to give the 100% of their capabilities.

Although V̇O2peak is not the same as V̇O2max, someone with a larger V̇O2max would be expected to have a larger V̇O2peak, and vice versa.

To simplify things. The greater the so-called aerobic capacity, or the maximum amount of oxygen the body can use during exercise, the better our cardiovascular and cardiorespiratory health.

LOSS OF MUSCLE MASS RESULTS IN WORSE CARDIORESPIRATORY FITNESS

We begin with a survey conducted in 1988 in healthy, non-overweight people aged 22-87 years.

Therefore, we observe that over time, we have a decrease in muscle mass and a corresponding decrease in cardiorespiratory fitness.

But what if there are other factors that influence? It would be desirable to completely disentangle age from our topic.

Sure. Hormone levels that drop over time could provide an explanation. Also, we could say that creatinine levels are affected by meat consumption and kidney health.

So to disentangle age, we proceed to a study conducted in 2016, in which young and middle-aged rowers were selected.

Here we see that less muscle mass is associated with worse cardiovascular fitness in both younger and older individuals.

And to leave no room for doubt, we are leaving the sports population and moving on to a study conducted in 2017, in which women who exercised in combination with diet were found to have better cardiorespiratory fitness than those who only dieted.

Although this may not be enough to make much of an impression at first, note that the women who only followed the diet lost about 2% of their total muscle mass, while exercise prevented this in the other group.

Do we start and see the connection?

MUSCLE MASS EQUALS CARDIOVASCULAR FITNESS

So, we move on to a study done in 2011. It found that V̇O2max per kg body weight grossly underestimates the true aerobic capacity in overweight subjects with normal glucose metabolism.

Usually individuals like that, have more muscle mass and strength than leaner ones, as calorie sufficiency provides better conditions for anabolism.

Previously we saw a connection, I hope that gradually we are becoming more confident.

Let's move on to a recent study which analysed data from another one, from 2013.

I think that this could not be any clearer. Muscle mass is directly related to cardiorespiratory fitness.

WHY DOES MUSCLE MASS INCREASE CARDIOVASCULAR FITNESS

As can be seen, the addition of muscle mass, if it has sufficient oxidative capacity (mitochondrial density/number, myoglobin content and capillarity), will increase oxygen consumption expressed in absolute terms.

From the above we can therefore conclude that muscle is an important factor affecting cardiorespiratory fitness, along with cardiac output and the difference in blood oxygen content between arterial and venous blood, at least in healthy, non-obese people.

BUT THIS DOES NOT JUSTIFY OBESITY

It's important to say it again to emphasize: muscle can be an important factor affecting cardiorespiratory fitness in healthy individuals without obesity.

The fact that muscle mass is linked to cardiorespiratory fitness is no reason to give up aerobic exercise and focus exclusively on weights while eating more than our daily requirements every day.

Previously, we explained that people who are overweight, but with normal glucose metabolism, usually have more muscle mass and strength than leaner people, as calorie sufficiency provides a better millieu for anabolism.

When we reach the level of obesity, however, things change. It is well known that strength increases with weight, but this is relative, as when it is normalized according to body mass, then the effects are worse in adults.

You see, insulin resistance, which occurs with the systematic consumption of calories above our daily needs, is associated with difficulty in muscle anabolism and a greater ease of their catabolism, a phenomenon known as anabolic resistance.

In a nutshell, obesity equals difficulty in gaining and ease in losing muscle mass.

And of course, when we slowly pass the stage of simple insulin resistance and daily excessive calorie consumption leads us to the stage of diabetes, then muscle loss and microvascular damage are one of the first things that happen.

Therefore the optimum is to maintain a relatively low body fat, so that there is insulin sensitivity and perform weight-bearing exercise at the same time.

To sum up, once again we see that muscle strength is the key to longevity.

-Suprastratum: The authority on health, fitness and nutrition

Sources/bibliography/more reading:

• Fleg JL, Lakatta EG. Role of Muscle Loss in the Age-Associated Reduction in VO2 Max. J Appl Physiol (1985), 65 (3), 1147-51 Sep 1988.
• Kim C-H, Wheatley CM, Behnia M, Johnson, BD. The Effect of Aging on Relationships Between Lean Body Mass and VO2max in Rowers.PLoS One, 11 (8), e0160275 2016 Aug 1 eCollection 2016.
• Weiss EP, Jordan RC, Frese EM, Albert SG, Villareal DT. effects of weight loss on lean mass, strength, bone, aerobic capacity.Med Sci Sports Exerc, 49 (1), 206-217 Jan 2017.
• Savonen K, Krachler B, Hassinen M, et al. The Current Standard Measure of Cardiorespiratory Fitness Introduces Confounding by Body Mass: The DR's EXTRA Study. Int J Obes (Lond), 36 (8), 1135-40 Aug 2012.
• Ten Hoor GA, Plasqui G, Schols AMWJ, Kok G. A Benefit of Being Heavier Is Being Strong: A Cross-Sectional Study in Young Adults.Sports Med Open, 4 (1), 12 2018 Mar 1.
• Lambert, CP. Whole Body Fat Free Mass and Vo2peak in Recreationally Active Men and Women. aerospace Medicine and Human Performance, Volume 91, Number 2, February 2020, pp. 102-105(4).
• Lambert CP, Winchester L, Jacks DA, Nader PA: Sex Differences in Time to Fatigue at 100% VO2 Peak When Normalized for Fat Free Mass. Res Sports Med, 21 (1), 78-89 2013.
• Tomlinson DJ, Erskine RM, Morse CI, et al. The Impact of Obesity on Skeletal Muscle Strength and Structure Through Adolescence to Old Age. biogerontology, 17 (3), 467-83 Jun 2016.
• Tallis J, James RS, Seebacher F. The Effects of Obesity on Skeletal Muscle Contractile Function.J Exp Biol, 221 (Pt 13) 2018 Jul 6.
• Tsintzas K, Jones R, Pabla P, et al. Effect of Acute and Short-Term Dietary Fat Ingestion on Postprandial Skeletal Muscle Protein Synthesis Rates in Middle-Aged, Overweight, and Obese Men.Am J Physiol Endocrinol Metab, 318 (3), E417-E429 2020 Mar 1.
• Beals JW, Skinner SK, McKenna CF, et al. Altered Anabolic Signalling and Reduced Stimulation of Myofibrillar Protein Synthesis After Feeding and Resistance Exercise in People With Obesity.J Physiol, 596 (21), 5119-5133 Nov 2018.
• Guerrero N, Bunout D, Hirsch S, et al. Premature loss of muscle mass and function in type 2 diabetes.Diabetes Res Clin Pract, 117, 32-8 Jul 2016.
• Khalil H. Diabetes Microvascular complications-A Clinical Update.Diabetes Metab Syndr, 11 Suppl 1, S133-S139 Nov 2017.

V̇O2max:

• Hill AV, Lupton H. Muscular Exercise, Lactic Acid, and the Supply and Utilization of Oxygen. QJM: An International Journal of Medicine, Volume os-16, Issue 62, January 1923, Pages 135-171

Other research suggests a correlation between muscle mass and aerobic capacity:

• Frontera WR, Meredith CN, O'Reilly KP, Evans WJ. Strength Training and Determinants of VO2max in Older Men.J Appl Physiol (1985), 68 (1), 329-33 Jan 1990.
• Hagerman FC, Walsh SJ, Staron RS, et al. Effects of High-Intensity Resistance Training on Untrained Older Men. i. Strength, Cardiovascular, and Metabolic Responses. j Gerontol A Biol Sci Med Sci, 55 (7), B336-46 Jul 2000.
• Neder JA, Nery LE, Silva AC, Andreoni S, Whipp BJ. Maximum Aerobic Power and Leg Muscle Mass and Strength Related to Age in Non-Athlethic Males and Females. Eur J Appl Physiol Occup Physiol, 79 (6), 522-30 May 1999.