Isometric training is used in different field such as, rehabilitation, physical preparation of athletes but as well in the general population.
An important scientific paper: “Isometric training and long-term adaptations: Effects of muscle length, intensity, and intent: A systematic Review, in 2018 has examined adaptations of different types of isometric training on morphological, neurological,
and performance variables.
This contraction is used in the resistance training to increase muscle mass, tendon quality, strength, power and range of motion but as well to delay the muscular fatigue and improve the voluntary activation of those muscles.
What are the advantages of the Isometric training in rehabilitation and resistance training?
- allows to undertake a training even if is present pain, because can be used in the pain free ankle of motion and further will be beneficial to reduce the pain with an acute analgesic effect altering excitatory and inhibitory functions in the corticomotor pathways.
- The total overload in isometric contraction is greater than in concentric contractions
- Can be used to improve the performance and to prevent injuries; understanding athlete’s weak points along the joint motion or specific movement, it can be used to address them, and the result can be after transfer to the performance
- can elicit changes in physiological qualities including muscle architecture, tendon stiffness and health, joint angle‐specific torque and metabolic function.
How Isometric training should be delivered to obtain Hypertrophic gaining, strength gaining and tendon changes?
- Has been found that isometric contraction at long muscle lengths (LMLs) was superior to equal volumes of training at short muscle lengths (SMLs) for increasing muscle size. Therefore, an isometric contraction during a biceps curl will create more gaining if the elbow is flexed 20degree instead of 50degrees.
- LML tend to produce higher quantities of muscle damage, increasing mechanical tension, also provoke when compared to a greater blood flow occlusion, rates of oxygen consumption, and metabolite build up when compared to SML contractions. These metabolic factors are well established to contribute to muscular hypertrophy.
Nevertheless provoke an higher neurological adaption.
- Also, they found that higher volume and long‐duration contractions determine major muscular hypertrophy, in fact sustained contractions are known to restrict blood flow, reduce muscle oxygen saturation, and increase metabolite concentrations in the muscle stimulating hypertrophy via multiple local and systemic mechanisms.
Shorter time under tension and greater contraction intent or speed provoke strength gaining.
It means that if your aim is to improve strength, you need to use shorter time under tension focusing on increasing the weight if the purpose is the maximal strength, or increasing the speed contraction inf your intent is to improve the explosive strength.
Injured tendons tend to be less stiff, despite increased thickness due to a shift in viscoelastic properties. Additionally, tendinopathy negatively affects tendon structure, leading to increased
vascularization and overall thickness.
Increasing the stiffness through the training can lead to optimize the time and magnitude of force transmission between muscle and bone.
To make meaningful changes in the tendon thickness and stiffness the intensity should be between 70% and 100% of the maximal contraction.
Even in this case the LML training appear to be superior for the purpose.
Both “maximal strength training” and “explosive strength training” produced significant improvements in the aponeurosis area, Young’s modulus and tendon stiffness but only “explosive strength training” decreased tendon CSA(cross sectional area),tendon elongation, tendon strain.
References: Dustin J. Oranchuk DJ et al,(2018), Isometric training and long‐term adaptations: Effects of muscle length, intensity, and intent: A systematic review