Isometric training was largely popularised by Bob Hoffman and Dr John Zieglar following successful application to American Weightlifter, Bill March’s training regime in the 1960’s. Translated, Isometric means (iso) same (metric) length, and in it’s purest form consists of a static muscle action with no velocity component.

Strength can be defined as the muscles ability to exert force, and differs from power in that power is the amount of force expressed per unit of time. Strength provides the base for power production and is therefore a desirable athletic quality. The force exerted by the muscles is largely down to the number of motor units recruited and total time under maximum tension, with greater recruitment occurring at intensities above 85% of 1RM (1 functional iso lifting).

Traditional methods of improving maximum strength involve the maximum effort method, in which a load >90% is lifted for a low volume, traditionally 1-5 reps for 3-5 sets. However due to the velocity component of the maximal effort method, the total time spent under maximal tension is not optimal for motor unit recruitment. Research has shown isometric actions to recruit 5% more motor units (95.2%) than concentric (89.7%) and eccentric (88.3%) actions (Baubult, 2006). Therefore isometric training is a suitable method for increasing strength, with improvements occurring 15-20 degrees either side of the isometric angle position (Kurz, 2001)

Isometric holds require an athlete to hold a mechanically correct position for a prescribed duration. Use within novice athletes allows the athlete to learn the correct motor patterns. Isometric holds should be viewed as a pre-requisite to dynamic actions, for an athlete who is unable to hold a correct position will be unable to perform the movement dynamically. Isometric holds and dynamic movement can be combined so that the athlete emphasises the eccentric action, pausing at key positions for a prescribed duration. This technique can allow the athlete to learn correct recruitment patterns, gain kinesthetic feedback, and be subjected to a training effect through time under tension. Improvements in strength gains with this form of isometric training will be minimal at best, with application geared towards teaching technique in novice trainees.

This method involves a high yielding rate and high force magnitude, but short time under max tension. The athlete may perform this method through stepping off a relatively high box and sticking the landing in a position specific to the sport, and hold for a prescribed duration. This method can be used as an injury prevention technique aimed at force absorption, or as a method for teaching plyometric yielding, prior to incorporating an overcoming phase. The intensity of this technique is dependant on box height (0.3-1.0m) and should be monitored carefully.

Aimed at producing maximal force and recruiting the greatest amount of motor units possible, this method requires the to athlete to push of pull against an immovable object maximally for a duration of between 3-8s. This technique usually requires a power rack enabling the athlete to push or pull the bar against pins from various positions within the desired movement (short of lockout, mid-point, short of reversal). This method is extremely effective for strengthening specific ranges (sticking point) within lifts, which may be preventing the athlete from performing optimally. This method may also be applied to strengthening the end range of the movement, where the length tension relationship may prevent maximal force being applied and thus undertraining occurrs. In a sport specific context, isometric presses and holds may be applied to specific angles where strength is required, such as near full arm extension during a rugby hand off or a punch, or the jump position for a basketball player. The ability to maximally recruit the available motor units within these ranges would have a marked effect on power production from such positions.

Using loads between 120-150% of maximum concentric 1RM, the athlete, with the aid of a spotter, unracks the weight and holds it for a duration between 3-10s at various positions of the lift (spread over numerous sets). This method may not have as great recruitment capabilities as isometric pushes/pulls as the athlete is not attempting to push/pull the load, but merely support it, however this is a suitable option when a rack with pins is not available. During this technique, the athlete must concentrate on contracting the musculature maximally.

Developed by Dr John Ziegler and Bob Hoffman in 1962, FI training allows quantification and progression of isometric methods. The FI method also has a ballistic element, and may be more appropriate for developing starting strength. The FI method requires the athlete to unrack the weight from a specific height, enabling a 2-3 inch lift before holding the weight in position or driving the weight against pins. The weight is still held/driven at a specific angle, yet the preceding concentric lift allows the athlete to monitor progress. This method trains the athlete to overcome inertia and continue to produce maximal force.

Due to the high level of motor unit recruitment associated with isometric training, their efficacy as a potentiation exercise is excellent. During such methods, the athlete may perform a set of isometrics (3-10s) choosing from either pushes/pulls/heavy supports/FI’s in order to maximally recruit motor units and excite the nervous system. The athlete must then rest long enough for fatigue to dissipate, though not so long that a potentiation effect is lost (2-3 minutes). Following a recovery period, the athlete can perform a power or submaximal strength set. Due to the elevation in neural drive lasting from the isometric activation set, the athlete will now be able to perform the power exercise at a higher power output, perform more repetitions at a given submaximal intensity, or perform the same number of repetitions at a greater intensity.

The application of these methods may also be warranted to performing an antagonist activation set, followed by a agonist strength power set, similar to methods used by coach Dan Baker of the Brisbrane Broncos who has performed extensive research in this field.

Isometric holds can be used as a method of teaching correct technique to begginners, or for activating the desired motor units within a warm up with all athletes. Within a strength/power block, isometrics can be incorporated prior to a power based exercise, as a means of neural activation (see Christian Thibaudeau, Theory and application of modern strength training methods.). The same organisation can be used to enhance force output during a strength set.

Isometrics can be incorporated in order to strengthen a particular range, either sport specific, or a sticking point. This can be done by combining isometrics and dynamic lifts within a workout, within a set, or within a repetition.

Isometrics can be used under fatigue during high volume training in order to promote a hypertrophy response. Within a hypertrophy context, isometrics may be incorporated at the end of a set, or last set to fully fatigue the muscles. With the aim of fatigue, the athlete should attempt to exert force during the isometric for the longest duration possible.

Often isometric exercises are touted as being for advanced trainees and unsuitable for begginners. My personal opinion is that this is incorrect. Of course impact absorption iso’s and iso holds can be very useful for teaching plyometric progression, injury prevention, and exercise technique, but it is the high force producing, longer duration methods, such as pulls/presses, heavy support, and FI’s that are in discussion. My belief is that providing a necessary anatomical adaptation phase has been completed, isometric exercises provide novice trainees with a very safe, and highly effective method of developing strength, and increasing their potential to maximally recruit motor units, a quality often lacking in the novice trainee. Therefore I would reccomend the incorporation of isometrics alongside dynamic lifting exercises, with most trainees.

When injury is preventing an athlete from achieving full range of an exercise or performing an exercise dynamically, the use of isometric training modalities can enable the athlete to maintain strength during rehabilitation. With isometrics improving strength 15degrees each way from the specific angle at which they are performed, the athlete can gain strength through a greater range than allowed by dynamic training to a specific point. Isometric exercise also places a greater strain on tendon and connective tissues, therefore creating a greater stimulus from adaptation, and preceding dynamic actions following injury.

For an in depth discussion of isometric training refer to the below reference list.