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Just like you need a variety of exercises in any programme you need a variety of time focusing on specific muscle contractions, as each contraction type play their specific role in sport and everyday situations.
In EVERY dynamic movement there is always a coupling of eccentric to concentric contraction with an isometric occurring in the middle as the muscle fibres change their direction. Also of critical importance in the stretch shortening cycle (SSC) or an athlete’s reactive ability.
Eccentric - Isometric - Concentric
An eccentric (lengthening), an isometric (no change in muscle length, also known as amortisation), and finally the concentric (muscle shortening) phases. Each of these phases serve a purpose in every step, every movement, and every activity completed in both daily life and athletics.
What is an isometric?
Isometrics can be defined as in which the proximal and distal attachments of a muscle don't move in relation to each other; muscle length remains constant. It occurs when the force being exerted by a muscle equals the force being imposed on it by a load.
Why use isometrics?
In athletic movements the isometric phase is practically instantaneous with a nearly indistinguishable beginning and end. Yet, it is imperative to understand its impact on force development. For example, sprinting is predominately isometric in nature due to the fact you are trying to overcome the deformation of the ankle in response to the ground reaction forces every time you contact the ground.
Isometric training can elicit changes in physiological qualities including muscle architecture, tendon stiffness and health, joint angle-specific torque, and metabolic functions. The primary function of the tendon is to transfer forces between bone and muscle, facilitating joint motion. Tendons can increase in stiffness to optimise the time and magnitude of force transmission between muscle and bone.
Reasons to use Isometrics
1. isometric training allows for a tightly controlled application of force within pain-free joint angles in rehabilitative settings. Isometric contractions can also be used to provide an acute analgesic effect and allow for pain-free dynamic loading by altering excitatory and inhibitory functions in the corticomotor pathways.
2. Isometric training provides a means to induce force overload as maximal isometric force is greater than that of concentric contractions. In the (second video) of the single leg quarter squat max force of an 80kg male was recored to be 2943 N (x3.8 BW) @100 ms - in max velocity sprinting ground reaction forces reach x3 BW.
3. A practitioner who understands the physical demands of a sport may be able to utilise isometric training to focus on specific weak points in a range of motion that can positively transfer to performance and injury prevention.
Different types of isometrics
1. Yielding (vid 1) - maintaining a joint position whilst resisting an external force
2. Overcoming (vid 2)- exerting force against an immovable object. Then two types you can ‘explode to max’ by applying force rapidly or you can ‘grind to max’ in which you build gradually to max. For increased tendon stiffness, fast neuromuscular adaption and increased rate or force development ‘explode to max’ is better.
3. Co-contraction (vid 1) - agonist-antagonist pair will contract with the same amount of torque around the same joint. Due to the equivalent torques being applied, a net force of zero is achieved and thus, no motion will occur at the limb.
4. Quasi-Isometric (vid 3)- holding a position then rapidly switching to the other limb and having to maintain that specific joint angle when you land.
The goal of yielding isometrics is to maintain position which has a similar neural pathway as an eccentric, while the goal of overcoming isometric contractions is to produce movement which has a neural pathway similar to a concentric.
Variables
- duration, muscle length, intent, intensity, volume
Angle specificity (muscle length) is important due to the fact there is little crossover if not performed at the specific angle in a movement. Example would be if you wanted to develop stiffer and more reactive ankle tendons to help with sprinting or jumping performing them at a short calf muscle length may not carryover to due to the fact you wouldn’t contact the ground at that specific angle. Same goes for the counter movement jump or similar, they need to be performed at the angle in which the muscle fibres change from an eccentric to a concentric. Although there seems to be a greater carryover through a larger range of motion if performed at a long muscle length.
My favourite practical application
Just like all exercises isometrics are all on a spectrum that may require certain prerequisite capacities before completing. I would recommend having a certain degree of general isometric strength (yielding and sub 80% intent overcoming iso’s) before completing any of the quasi or overcoming Isometrics due to large forces at high speed going through the body.
1. Video 1 Long duration isometrics holds at long muscle length for tendon health - 30s to 5 minutes. Will use short 20-30s at the start of session for activation or analgesic effect or at the end of the go session go for max time!
- Weighted split squat iso 30s+
Video 2 - Single leg hip thrust hold - be surprised how many people struggle to maintain and hold good hip extension and pelvis position so this is a great one. 30+
Video 3etc… Foot isometrics - feet transfer the body’s energy into the ground if they are weak and unable to tolerate load that is the leak link in the chain! 30s+
2. Video 9 - Maximal overcoming calf iso into pogos using post activation potentiation. This method can be used in many situations just do the isometric in the specific position in which the fibres change from eccentric to concentric. 1-2 maximal iso into explosive effort.
3. Videos 5, split squat drop, hamstring switches - great for mimicking sport due to the fact your body will undergo high forces at high velocities. Will use a standalone exercises due to high neuromuscular demand. Great to train the ability to decel.
The ability too rapidly develop isometric force is clearly of critical importance for the majority, if not all, sports. In these situations it is ideal that the athlete be capable of producing high levels of force rapidly in order to transfer through these three muscle action phases at the highest velocities possible.
Time is almost always limited due to the attempt of an athlete to complete the desired skill in the highest velocity available to them. If one is not able to rapidly achieve the isometric force required within the brief amount of time available, successful performance becomes much less likely.
In summary…
Low energy cost, maximal recruitment, minimal mechanical damage, low time cost, can be used in high frequency, high recovery rate, low technical requirement, limited hypertrophic response, specific, overload running forces.
References
Triphasic Training - @Cal Dietz
Isometrics for performance - @Max Schmarzo
Oranchuk, D. J., Storey, A. G., Nelson, A. R., & Cronin, J. B. (2019). Isometric training and long‐term adaptations: Effects of muscle length, intensity, and intent: A systematic review. Scandinavian Journal of Medicine & Science in Sports, 29(4), 484-503.
Hasler EM, Denoth J, Stacoff A, Herzog W. Influence of hip and knee joint angles on excitation of knee extensor muscles. Electromyogr Clin Neurophysiol. 1994;34(6):355-361.
Krebs DE, Staples WH, Cuttita D, Zickel RE. Knee joint angle: Its relationship to quadriceps femoris activity in normal and postarthotomy limbs. Arch Phys Med Rehabil. 1983;64(10):441-447.
Abbott BC, Wilkie DR. The relation between velocity of shortening and the tension-length curve of skeletal muscle. J Physiol. 1953;120(1):214-223.
Tsoukos A, Bogdanis GC, Terzis G, Veligekas P. Acute improvement of vertical jump performance after isometric squats depends on knee angle and vertical jumping ability. J Strength Cond Res. 2016;30(8):2250-2257.
Burgess K, Connick M, Grahm-Smith P, Pearson S (2007) Plyometric vs. isometric training influences on tendon properties and muscle output. Neuromuscular implications and applications to resistance training. Journal of Strength and Conditioning Research 21(3):986–89.
