What Are The Benefits of High Intensity Strength Training (HIT)

I am a big believer in understanding the why behind things that I do. Maybe this is partially due to the “Laziness Factor” and its application to the principle of “Not doing something for nothing.”

High Intensity Training is by its very definition is “hard”. So, if you are like me and want to know what the benefits are for working so hard here are some of the benefits outlined by HITUni (an educational resource on high intensity training). 

The benefits of high intensity exercise for the skeletal system

  • Increased bone mass/density
  • Strengthening of joints, tendons, and ligaments
  • Reduction in pain caused by joint diseases, like osteoarthritis and rheumatoid arthritis, and lower back pain
  • Enhanced flexibility

Acute and chronic effects of High Intensity Training on muscle tissue

  • Maximal local aerobic metabolism; anaerobic and aerobic glycolysis (leading to an increase in VO2/oxygen consumption)
  • Increase in blood lactate
  • Increase in AMP (adenosine monophosphate), ATP (adenosine triphosphate) ratio, resulting in: activation of AMPK (adenosine monophosphate-activated protein kinase pathway) during exercise
  • Increase in mitochondrial enzymes
  • Increase in mitochondrial proliferation
  • Decrease in type IIx fibers
  • Increase in type IIa and type I fibers
  • Increase in capillary contacts
  • Increase in capillary fiber ratio (enabling an increase in blood supply to active muscle and an increased ability to remove lactate)
  • Improved oxygen delivery and use of oxygen within the muscle fiber
  • Hypertrophy


Acute hypertrophy: Sarcoplasmic hypertrophy

Sarcoplasmic hypertrophy refers to an increase in volume of muscle cell sarcoplasm (the muscle cell equivalent of cytoplasm).

There is an increase in glycosomes, an increase in the number of ATP producing mitochondria and an increase in the concentration of enzymes for cellular respiration. These components make up about 20% of a muscle cell.

These changes enable the cell to produce a greater amount of ATP, used to create energy during muscular work. As well as increasing the ATP supply, sarcoplasmic hypertrophy increases the diameter of muscle, whilst reducing its density.

Chronic hypertrophy: Myofibrillar/Sarcomere hypertrophy

Myofibrillar hypertrophy is the growth of the muscles contractile elements: an increase in actin and myosin filaments, sarcomeres and myofibrils.

During resistance exercise, tension builds up in the muscle fibers, over the course of a set of an exercise. This causes damage to the cross-bridges between the actin and myosin filaments; the sarcolemma ruptures and leaks calcium. A build up in calcium ion levels follows, in the intracellular space. Enzymes, known as calpains, are released to clear the damaged contractile tissue. Then, immune system cells are called into play to remove the damaged fibers. Muscle cells in proximity to the ruptured sarcolemma begin to make and release growth factors.

Satellite cells are also activated to begin repairing the damaged muscle fibers and encourage muscular growth. Satellite cells become myoblasts, which differentiate into muscle cells and fuse to already existing muscle fibers at the damage site, adding their nuclei to the muscle cells.

The muscle fibers are then able to produce greater amounts of actin and myosin. The extra myofibril filaments increase the strength of the muscle and its contractile ability, making the muscle denser.

A total of the acute and chronic adaptations to high intensity resistance training lead to:

  • An increase in muscular hypertrophy and muscular density
  • Strength and endurance
  • CNS becomes more skilled at utilising muscle tissue
  • An improvement in musculoskeletal flexibility
  • An increase in VO2 max
  • An improvement in cardiovascular function
  • An increase in economy of movement
  • Increased functional capacity of internal organs
  • Reversal of age signature for many genes
  • Improved posture and physical appearance

Acute and chronic effects of High Intensity Training on the cardiovascular system and metabolism

  • Maximal Local Aerobic Metabolism is achieved in working muscle tissue
  • There is an increase in oxygen consumption (VO2) consumption
  • There is an increase in blood lactate levels, as glucose is broken down and oxidized to pyruvate, which then produces lactate at an amount greater than the tissues can remove it
  • There is an increase in the adenosine monophosphate (AMP) to adenosine triphosphate (ATP) ratio due to the increased use of ATP for energy. This results in an increase in activity of the adenosine monophosphate-activated protein kinase pathway (AMPK)
  • There is increased shear rate (flow velocity) of blood in the vasculature
  • There is an increase in peripheral vascular blood pressure (there is far less or no change in myocardial pressure)
  • There is an increase in venous return of blood to the heart
  • There is an increase in left ventricular function (the left ventricle is responsible for pumping oxygenated blood into the body)
  • There is an increase in heart rate, the number of times the heart beats per minute
  • There is an increase in cardiac output, as a greater volume of blood is pumped by the heart per minute
  • Increase in mitochondrial enzymes
  • Increase in mitochondrial proliferation
  • Decrease in type IIx fibers
  • Increase in type IIa and type I fibers
  • Increase in capillary contacts
  • Increase in capillary fiber ratio
  • Increase in VO2 max
  • Increase in economy of movement
  • Decrease in resting heart rate

HIT may stimulate left ventricle hypertrophy in the heart, although evidence for this is not conclusive at this time. If this proves to be the case, then this hypertrophy adaptation would likely improve heart pumping mechanics and cardiac output or stroke volume.

Physiological benefits for the cardiovascular system (CV)

  • A general decreased risk for coronary artery disease because HIT can help combat physical inactivity, obesity, dyslipidemia and prediabetes, all factors of CHD
  • For those with existing coronary artery disease, decreased risk of adverse clinical events by increasing cardiorespiratory fitness
  • Increase in the release of the hormone adiponectin
  • Improved ratio of low-density lipoproteins and high-density lipoproteins in the bloodstream
  • Improved cardiorespiratory fitness
  • Improved oxygen delivery and oxygen uptake within muscle fiber, due to increase in aerobic enzyme activity, increase in capillary density, improvement in blood supply and ability to remove lactate and increase in concentration of cellular mitochondria
  • Improved coronary blood flow, while decreasing the amount of resistance against which the heart has to pump
  • Blood pressure normalisation: HIT reduces resting blood pressure for those who are mildly hypertensive
  • Strength training has been shown to improve cholesterol/blood lipid levels, after only a few weeks

Physiological benefits of exercise related to digestion, metabolism and fat storage

  • Decreased gastrointestinal transit time or the speed at which food moves from the stomach through the intestines and final through the colon
  • Decreased risk of colon cancer
  • Increased metabolic rate, which leads to the body using more energy on a daily basis
  • A positive impact on weight loss and/or weight management
  • A positive effect on chronic diseases, related to obesity, such as coronary heart disease, stroke, hypertension, type 2 diabetes, dyslipidemia and some cancers
  • Increased glucose metabolism – strength training increases glucose metabolism by 23% after just 4 months of working out
  • Decreased risk of diabetes
  • Increased insulin sensitivity
  • Increased release of fatty acids, due to hormone-sensitive lipase release
    Many of these benefits can also be attained by other training methods but with HIT we are aiming to attain to attain these benefits in a time efficient and safe manner with a training method that is sustainable