Possible health related advantages and disadvantages of isotonic, isometric and isokinetic resistance exercises with comparison to aerobic exercise
Looking at resistance exercises there are three types, these include: isotonic, isometric and isokinetic resistance exercises. These different types were looked at and the possible health advantages and disadvantages were identified. As part of these studies, a comparison look was taken against aerobic exercise for measure as well. The results were variable, and it must be said that all arguments for and against each resistance exercise is valid.
Keywords: Isotonic, Isometric, Isokinetic, resistance, exercise, health.
Resistance training is any activity that causes muscles to contract against external force. Since the goal of resistance training is to progressively overload the musculoskeletal system, weight machines, dumbbells, and barbells are usually used as a resistance. Studies demonstrate that regular progressive resistance training develops the strength and size of muscles 1 and increases bone mass 2 in individuals which include young male athletes and older women. It also decreases blood pressure and increases endothelial function. These positive changes in arterial function may partially explain why resistance training is associated with improved health outcomes 3.In addition, resistance exercise might be even more beneficial than aerobic exercise for fat loss because it triggers much more muscle strength 4.
Isotonic resistance is a type of resistance exercise which keeps equal tone of muscle by shortening the contracting muscle against the outside load 5. There are two different types of isotonic contractions eccentric and concentric. Eccentric contractions lead to the lengthening of the muscle because there is less tension generated by the muscle in comparison to the force produced by the load. Concentric contractions lead to muscle shortening because of the greater tension generated by the muscle in comparison to the force produced by the load 6. Increase in heart rate is one of the benefits of isotonic resistance which will in turn increase circulation of blood to the rest of the body and allow for optimum functionality of organs and tissues 7. It is evident that isotonic exercise may be used to reduce impairment for people suffering from stroke 8. Isotonic exercise has the potential to reduce pain while continuing sport activities, thus isotonic muscle contraction (heavy slow resistance 3-5 times per week) result in significant reduction in pain within a 12week program 9. While on the other hand strenuous, long term endurance in exercise induces suppressed immune function and increase risk of infections, tissues may develop slowly causing chronic pain 10.
Isometric resistance exercise is a form of physical activity through which muscular action contraction occurs producing a force but at the same time the length of the muscles remaining unchanged 11. This exercise does not include the movement of joints instead the muscle fibres are held in position against the resistance 12. According to 13 when muscle experience a constant tension due to isometric exercise the heart and respiratory functions are affected leading to an increase in the heart rate, blood pressure, pulmonary ventilation. Isometric exercise is more preferable than isotonic and isokinetic resistance exercise because it is more convenient for home maintenance since less equipment are required to perform activities related to it and it is much simpler to understand how it works 14. Pressure, bone damage, and internal articular inflammation are much less common in isometric contraction as compared to other two resistance exercises 15. Isometric exercises are cost effective and serve as an important strength booster 16. This form of exercise has a positive effect in that it is able to increase muscular contractions (positive inotropic) and it also has a positive chronotropic 11. According to a study conducted by 17 performing isometric exercises daily for 10 minutes can lead to a more strengthened neck, upper and lower limbs, and ventral part (the back). The only disadvantage of these exercises is that your body weight is equal to resistance, no external or additional force is included 17.
Isokinetic resistance exercise is a combination of Isotonic (weight-lifting ) and Isometric(plank-pose) exercise. It enables muscles to apply most extreme strength within the scope of all muscle joint movements at a steady speed, this practice strategy can be utilized to enhance muscle strength 18. Isokinetic exercise involves muscle contractions that occur under constant tension and speed. This form of exercise involves the muscle applying maximum force throughout the movement. According to 19, at the present time all examination which analyzes the strength gains made by the utilization of older techniques of straight training with gains made by the utilization of isokinetic training has demonstrated that strength gains are greater and are made quicker with isokinetics than with some other methods tried 19. It appears that in spite of the fact that isokinetics might be a prevalent method in strength development,however,it may not be best to develop explosive movements where the speed of the movement is the ultimate goal or concern 20. A study conducted by 21 showed that there was a greater cardiovascular response for submaximal isokinetic concentric movements (shortening of muscle fibres) than in eccentric isokinetic movements (lengthening of muscle fibres). This means that there was a greater increase in the heart rate, mean arterial blood pressure and rate pressure-pressure products during isokinetic muscle contractions. Physiological adaptations that occur due to progressive resistance training results in physiological adaptations such as a decrease in the resting blood pressure but has no significant effect on the resting heart rate 22
Aerobic exercise uses a lot of energy as more oxygen is used than other types of exercises like dynamic resistance exercise. During a short –term, light to moderate exercise of aerobic exercise causes the cardiac output to increase as oxygen is carried out by the body in order to form ATP 23. Cardiac output will be directly proportional to the stroke volume (SV) and heart rate (HR). These are exercises that involve large muscles groups which relies on aerobic metabolism and oxygen to fuel up and increase cardiovascular fitness 24. Examples of aerobic exercise are walking, jogging, running, cycling, hiking, swimming, and they are accessed through aerobic capacity 25. Health benefits include an increase in heart rate and respiratory rate as it is an exercise that increases maximal uptake of oxygen, so this causes the heart to deliver oxygenated blood to the muscles then stimulate healthy blood flow 26. This exercise causes resistance to negate mind health like bad moods and stress, as the exercises release hormones that reduce this condition, e.g. endorphin hormone which results in relaxed good mood 25. Comparing both exercises on the cardiovascular fitness health, aerobic is more beneficial as it can be used as a preventive measure on patients that are diagnosed with cardiovascular diseases 27. Both exercises might have their own differences, but both have a unique and positive impact on improving health 24.
In conclusion isotonic resistance exercises seems to be ideal for strength gains and muscle growth and seems to have a positive response in eliminating previous injuries through strength gains. However, it would seem that the downside includes damaged joints if improperly applied to a specific individual.
Isometric resistance exercises are the most cost effective and ideal for smaller spaces as no external equipment is needed, benefits include a much lower risk of joint injury and much easier to perform the only downside seems to be that the resistance provided can only ever be as great as the individuals own body weight.
Isokinetic resistance exercises require a very specific attention to detail, this type of resistance exercise shows promise in muscular strength, growth and endurance however because of the specific attention to detail form is extremely important.
Aerobic exercise at a sub-maximal level shows superior fat loss capabilities as opposed to resistance training, however, at a maximal level there are many cardiovascular health benefits as well but with this comes the increased risk of injury and immune suppression.
The main consensus on the health benefits related to resistance exercise seems to all point to the same thing and that is that it depends on the individual’s current health status, age, gender and goals of exercise.