The Truth Behind Isometric Training

Isometric training has been around for many years. Legendary strongman Alexander Zass preached the effectiveness of isometric training in the early 1900’s. As he found himself a prisoner of war during World War 1, Zass began pulling and pushing on the bars and chains used to constrain him. He quickly began to notice an improvement from his efforts. It was long after that Zass began promoting this style of training through popular mail order courses. Zass has been attributed as the Father of Isometrics.



Common practice and beliefs
Isometric training does not require expensive equipment or a gym, it can be performed anywhere, with little time necessary. Although there is a great deal of advantages to isometric training in general it is used in athletics as a supplement. The thought behind this is that it lacks the specificity for athletics in terms of dynamic movement. Further, it is thought that strength gain will occur at only the angle the isometric contraction is trained at and produce little to no strength gain at other angles. The final common belief is the use of isometric training can produce a great deal of strain on elite athletes and at times cause pain and overload the CNS system.


Defined
Isometric muscle action is a muscle action where the muscle does not change in length because the tension in the cross-bridges is equal to the resistive force (Baechle, 2008; Coburn, 2012; Zatsiorsky, 2006; Weinberg, 2007; Powers, 2007). There is little to no change in muscle length or actual movement (Baechle, 2008; Coburn, 2012; Zatsiorsky, 2006; Weinberg, 2007; Powers, 2007).
Examples:

1. Holding a weight at a certain position in the range of motion. Example holding a barbell at 90 degrees.

2.          Pushing or pulling against an immovable external resistance. Example pushing against a wall.

    3.       Holding your body in a certain position in a range of motion: holding the chin-up at 90 degrees.

Muscle Activation

A very significant benefit of isometric action training is that it produces a greater level of activation than any other contraction regimen. The term activation is referring to the recruitment of the muscle motor units.
During 2001 a study on “Activation of Human Quadriceps Femoris During Isometric, Concentric, and Eccentric Contractions” by Nicholas Babault et al. found that during maximal eccentric and concentric contractions activation levels were 88.3% and 89.7%, respectively, yet they were significantly lower (P<0.05) than the activation levels during maximal isometric contraction which were 95.2%. This study’s findings have been well documented and supported through the large body of literature that has found maximal isometric action to recruit nearly all the motor units (Allen, 1995; Allen, 1998; Belanger, 1981; De Serres and Enoka 1998; Merton, 1954; & Newham, 1991). This demonstrated that through the use of isometric training we are capable of engaging a greater percentage of our muscle fibres. Therefore, in theory we should be able to have improvement in our capability of muscle activation through development of our neural system. If this proves to be true we may find a significant increase in our strength based on our capability of using our muscle closer to its full potential.

Strength Gain
Isometric training has been used by many athletes and trainers to deal with sticking points (nothing more nothing less). This has occurred because many trainers have thought that isometric training only increases strength at the angle trained. This is partially true, in the study done on the “Specificity of Joint Angle in Isometric Training” by Kitai and Sale found that strength gains were the greatest at the angle the training occurred. However, significant increase in strength also occurred at the angles (+/-5 degrees). Some studies have found 20-50% strength transfer gained in a range of +/-20 degrees; a large portion of the literature completed on this topic supports that strength is either exclusive to or greater at the joint angle trained, in comparison to other joint angles (Enamait, 2005; Bender, 1963; Gardner, 1963; Meyers, 1967; Raitsin,  1974; Lindh,  1979; Thrpaut-Ma-thieu, 1988).  In order to practically resolve the issue of strength gain only occurring in a limited range of degrees around the trained area, many strength coaches have begun to implement a series of isometric contractions throughout the range of motion.

There is no doubt in the body of literature that isometric training can lead to significant strength gain.  As isometric training spread throughout the early 1900’s and became popular during the 1950’s significant research began to come out. One such example is T. Hettinger and E. Muller (1953, 1955, 1958) who found that a daily effort of 2/3 maximum effort, for a period of 6 seconds, had the ability to increase strength by up to 5% per week. Studies have found strength gains in ranges of 14-40% over 6-10 week periods (Kanehisa, 2002; Kitai, 2001; Bender, 1963; Gardner, 1963; Meyers, 1967; Raitsin, 1974; Lindh, 1979; Thérpaut-Mathieu, 1988)


Based on this we can conclude that:

1. Intramuscular tension is greater and attained for a longer period of time in maximal isometric action training than dynamic exercises. This can be attributed to the fact that dynamic exercise has velocity and acceleration aspects; force is only produced for split seconds. During maximal isometric action training, it is possible to sustain the maximal tension for 3-6 seconds. However, dynamic exercise on the concentric portion maximum intramuscular tension lasts for 0.25-0.5 seconds. Yuri Verkhoshansky (1977) found that every 6 second isometric contraction is equal to numerous dynamic contractions. Also, The ability to increase strength is greatly affected by the amount of total time the body is under maximal intramuscular tension per session. By adding 10-20 seconds of intramuscular tension per session, one is capable of dramatically increasing the potential for strength gains (Thibaudeau, 2004).
2. Isometric training has the ability to assist in surpassing sticking points and weak angles in an athlete’s range of motion by allowing them to improve at a precise point in the range of motion. For weight lifters this can be extremely useful in overcoming plateaus.
3. Isometric exercise does not require a great deal of energy expenditure. This means one can receive the benefits of isometric action training without having a drastic effect on the remaining training session.

Hypertrophy
A large factor in why isometric training has not fully developed its self in the masses is due to phenomenon of bodybuilding that took place. As body building began to really become popular simultaneously it was being hypothesized that isometric training would produce insignificant muscles gains in comparison to dynamic training due to the absence of work. In response to this hypothesis, bodybuilders pushed aside isometric training and focused on exercise deemed more appropriate for hypertrophy. As the popularity of body building further increased, isometric training found itself further and further into obscurity. However, the recent findings in isometric training have thrown the old hypothesis out and have findings supporting that isometric training can in fact lead to hypertrophy.

        In the study looking at Effects of Equivolume Isometric Training Programs Comprising Medium or High Resistance on Muscle Size and Strength by kanehisa et al. 2002 found that over the course of a 10 week program, training 3 times a week there was significant increase in muscle volume in groups performing at 100% and 60% maximum voluntary isometric contractions. However, the group performing 100% maximum voluntary isometric contractions had significantly greater muscle volume gains than the 60% group. The maximal isometric group had an increase in muscle volume by 12.4% and the 60% group had a 5.3% increase. The authors concluded that the reason for the increase in muscle volume is unknown but could be attributed to the metabolic demands and endocrine activities rather than mechanical stress and neuromuscular control. The difference in muscle volume between the 100% group and the 60% may be attributed to the combination of prescribed intensity and number of sets in the protocol which may have induced a greater contribution of either metabolic or hormonal stimuli.


Isometric Styles
The names of the following styles vary from study to study and book to book. However, the following categories are separated the same way by nearly everyone.


Overcoming isometric:
This category is when one is pushing against an immovable resistance. For example assuming you are not as powerful as Samson you can place yourself between two pillars or in a squat rack place one hand on each post and push as hard as you can with the intent to move the resistance (Judges 16:29). Fig. 1

Yielding Isometric:
A weight or object is being held and prevented from lowering or eccentric contraction occurring. In this scenario, the intent is not to move an object, rather to stop it from moving.
Whenever these techniques are used, it is important to note that they do not have the same effect on the neural patterns. Yielding isometrics has a greater impact in eccentric strength and muscle mass and overcoming isometric has a greater impact on concentric strength (Thibaudeau, 2004).


Maximal Effort Isometrics:
This style is performed by applying maximal tension to an immobile structure. Tension should be generated quickly and held for 3 to 6 seconds (Enamait, 2005; kanehisa, 2002). This form of training is an excellent means in improving strength, muscle volume, and improve torque. However, the improvement of torque to muscle volume ratio is more effective in other forms of isometric training (Enamait, 2005; kanehisa, 2002).


Whether or not tension should be developed quickly or gradually over a period of 4-5 seconds, it is the most commonly debated topic in regards to isometric training. In terms of developing explosive strength and power, producing tension quickly is optimal. Fleck and Kramer (2004) note that by producing maximal tension rapidly, one imposes significant adaptation in contractile muscle properties, such as, the excitation- contraction coupling pathway. However, when looking at risk to benefit ratio it becomes a tricky situation, since, the risk of injury is significantly higher when tension is developed quickly.


“Excitation–contraction coupling is broadly defined as the process linking the action potential to contraction in striated muscle or, more narrowly, as the process coupling surface membrane depolarization to Ca2+ release from the sarcoplasmic reticulum (Dulhunty, 2006).”


Max Duration Isometric:
In the case of max duration isometric exercise, you are pushing, pulling, or holding a sub maximal load for as long as possible. This is likely the most common form of isometric seen used in the general population. The sets used generally range from 20 to 60 seconds in length. This form of training can be effective in the development of muscle volume and is a good method for training muscle endurance and creating a high level of micro muscle damage (Thibaudeau, 2004).
When practically applying this method, one can use yielding or overcoming isometrics. However the preferred form by most is the yielding isometrics. When one is training the load should range from 50-80% for duration of 20-60 seconds.


Explosive Isometrics (ballistic isometrics):
            This method focuses on developing tension as quickly as possible. Tension is produced for brief burst of 1-3 seconds. The goal is to reach full force as quickly as possible. This method has been found to develop speed and strength (Thibaudeau, 2004; & Enamait, 2005). This method of isometric training has a high level of crossover to athletic performance. This form of isometric training is often used in martial art training.


            Behm and Sale looked at “Intended Rather than Actual Movement Velocity Determines Velocity Specific Training Response” (1993). They found that repeated attempts to perform ballistic contractions with high rate of force and tension development were the primary stimuli for high velocity training response to occur. This resulted in the authors concluding that the form of either isometric or concentric muscle actions is not important to speed development. Rather, the intension to move fast was much more important than the actual speed of the movement. When performing this method, one must perform it using overcoming isometrics. This method is extremely powerful in developing athletes particularly in sports where the athlete often starts from static position (sprinting out of the blocks, martial arts, football, etc).


            A practical example of the effects that can take place in sport through the use of weight training and explosive isometric training can be seen in the study by Olson and Hopkins (1999). The group that had been working with weights and explosive isometrics had significant increase in peak force and speed. This study further demonstrates that speed and peak force can be significantly improved when dynamic weight and isometric training are used as supplement to traditional training.


Static Dynamic Isometric training:
            This method involves supersets of isometric and dynamic work. This is done by beginning with a 3-6 second hold, followed by explosive dynamic work, for example, pressing the bar in bench-press as hard as you can into pins then doing explosive bench-press with full range of motion.


            Verkhoshansky (1977) found that static dynamic method of training is superior for developing speed and strength than dynamic training alone. The effectiveness of dynamic training improves when combined with preliminary static tension by up to 20%. When this training is being used, one must perform the dynamic aspect immediately following the static.
 Frequency, Duration, and Rest


            In 1981 Atha found that when isometric training is used properly it can be performed safely without the risk of over training on a daily basis for strength development. This is assuming that isometric training is acting as a supplement to your training and not acting as the sole form of training. However, the more recent literature demonstrated the optimal use of isometric training would be to perform 3-4 workouts per week with maximal voluntary muscle actions each held 3-6 seconds (Fleck and Kramer 2004; Enamait, 2005; & Verkhoshansky, 1977).  


As noted earlier, isometric training is very beneficial to have incorporated into your training a few times per week. When performing Isometric training, it is optimal to keep that aspect of your training brief to approximately 10 minutes (Verkhoshansky, 1977). The rest periods should be short at approximately 10 seconds between repetitions (Verkhoshansky, 1977).


When performing Isometric training, it is optimal to train at several angels through the range of motion. Each joint angle trained should be put under 4 to 6 reps. In between sets one should attempt to actively relax the muscle.


Why is Isometric Training Not Commonly Used?
With the incredible benefits of isometric training outlined in literature, it is difficult to understand how it could be so rarely used. As previously noted, the hypothesis that isometric training would have very little effect on hypertrophy and the simultaneous popularity of body building had a significant effect on the popularity of isometric training. To further worsen the scenario for isometric training during this time period many trainers decided to do selective reading associated with the disadvantages of isometric training. In, particular trainers placed an emphasis on Verkhoshansky (1977) listed negative aspects of isometric training:

1. Isometric fatigues the nervous system
2. Isometrics have a harmful influence on the cardiovascular system
3. Isometrics decrease coordination and speed of movement
4. Isometrics worsen the elasticity of the muscle

The majority of trainers were quick to point out the faults and potential draw backs. However, they chose to ignore that Verkhoshansky offered simple ways to avoid and negate all these issues through proper sequencing of work and rest, time for breathing, relaxation, and stretching.


Isometric training is a fantastic tool that has been underutilised. That being said one must not form their routine around isometric training, rather it should be supplemented into 3-4 days a week of your training routine. This tool has the capability of increasing your strength, power, speed, explosiveness, muscle volume, and breaking through plateaus. Many have thought isometric training to not be transferable to athletic performance. However, we see that the research does not support this notion.


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• Fig. 1 http://www.suncoasthillels.org/judaica/yoav-shtibelman-lindsey-st-pierre/