The Lowdown on Exercising for Longevity – Part 2.1

September 8, 2023
By Nathan Nikoloff
On March 10, 2023

Want to catch up with the other articles in this series?

Part 1: What is the impact of endurance training on human lifespan?
Part 1.1: What is VO2max?
Part 2: What are training zones?
Part 2.1: How do muscle fiber types correspond to training zones?
Part 2.2: Training zones 1, 2 and 3
Part 2.3: Training zones 3, 4, 5 and 6
Part 2.4: Moderate intensity vs. high intensity exercise
Part 3: By which mechanisms does exercise delay aging and prevent chronic disease?
Part 3.1: What are the cardiovascular adaptations to endurance training?
Part 3.2: What are the metabolic adaptations to endurance training?
Part 3.3: Can exercise prevent or even treat cancer?
Part 3.4: How does exercise impact the immune system?
Part 3.5: Exercise as a therapy for neurodegeneration and conclusions

Muscle fiber types

Before we deep dive into training zones, it is important to understand muscle fiber types. Each training zone is defined by the muscle fibre type being used and the underlying physiology.

The intensity of exercise elicits muscle fibre recruitment patterns with corresponding energy systems. This is the foundation of understanding training zones: as exercise intensity increases we escalate through the muscle fibre types. In the lower training zones, type I muscle fibers are recruited. These types of fibers have the highest mitochondrial density and content. Type I fibers oxidise fat; fat can only be oxidised in the mitochondria. Type II fibers, in comparison, have lower mitochondrial function.

Type I fibers

Type I fibers are slow twitch— they are slower to fatigue. We spend all day utilising these muscle fibers to live life, without them (hopefully) causing us any issues.
They contract at lower forces and therefore require less energy.
They utilise aerobic metabolism: they use oxygen to convert glucose or fat to energy.
We use fat tissue as an external energy supply.
On a chicken, this is the dark meat, in the legs and thighs which are used all day for walking. The dark colour is owed to their rich blood supply for importing fatty acids from adipose tissue, high amounts of mitochondria to oxidise fat and large amounts of myoglobin to store oxygen.
Type I fibers are predominantly utilised in zone 1 and 2 exercise.

Figure 2.1: Skeletal muscle fibre (credit Wikipedia)

Conversely, Type II muscle fibers are:

Faster to fatigue
Contract at much larger forces.
Store a local energy supply in glycogen, ATP and creatine phosphate
Contains a limited amount of blood supply and myoglobin
Lighter colour in colour (the white part of the muscle on a chicken) — its colour owing to the density of muscle fibers and lack of myoglobin, mitochondria and blood supply.
Type IIa muscle fibers are utilised in zone 3,4 and 5 and rely predominantly on glucose oxidation.
Type IIX muscle fibers produce the biggest force and rely on glucose, stored ATP and the creatine phosphate system.

Properties	Type I fibres	Type IIA fibres	Type IIX fibres
Motor Unit Type	Slow Oxidative (SO)	Fast Oxidative/Glycolytic (FOG)	Fast Glycolytic (FG)
Training zone	1,2 and 3	3,4 and 5	5 and 6
Energy substrate	Mainly Fats	Mainly carbs	Carbs, stored ATP and the creatine phosphate system
Twitch speed	Slow	Fast	Fast
Twitch force	Small	Medium	Large
Resistance to fatigue	High	High	Low
Glycogen content	Low	High	High
Capillary supply	Rich	Rich	Poor
Capillary density	High	Intermediate	Low
Myoglobin	High	High	Low
Red colour	Dark	Dark	Pale
Mitochondrial density	High	High	Low
Oxidative enzyme capacity	High	Intermediate-high	Low

Figure 2.2: Classification of muscles fibers (Adapted from Wikipedia)

Newer The Lowdown on Exercising for Longevity – Part 2

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03 Aug

Exercise

The Lowdown on Exercising for Longevity

August 3, 2023
Featured
By Nathan Nikoloff
1 comment

There is a powerful treatment that effectively delays the onset of death and preserves healthspan. This treatment is called exercise, and no other treatment or drug rivals its ability to prevent chronic illness.

The problem: it requires consistent effort and commitment over time and the myriad benefits of exercise cannot be packaged and sold as a medication. However, the long-term benefits of regular exercise, such as improved cardiovascular health, lower blood pressure, stronger muscles and bones, and better mental health, far outweigh the effort required to maintain an active lifestyle. These benefits also reduce the reliance on medication to prevent chronic diseases from developing.

The emerging science of longevity and optimising healthspan has seen increasing interest in both scientific and public forums. Much of the hype around longevity has surrounded advances in biology, with suggestions that pharmacological agents could target cellular aging processes and slow aging. There is little evidence to suggest this. There is however, evidence that exercise impacts both lifespan and healthspan. This becomes increasingly evident when reviewing the scientific literature on the impact of exercise on health parameters associated with aging.

The beauty of exercise is that it targets the whole human synergistically: from cellular processes through to multiple body systems and organs. The outcome of the right exercise prescription is an upgrade toward superior physiological and anatomical health. This upgrade comes with countless benefits, including suppressing the pathogenesis of all the major leading causes of death e.g. cardiovascular disease and cancer.

In this extended article on endurance training for longevity, I’ll be breaking down the profound effect of improving cardiorespiratory fitness on lifespan.