An isometric exercise is when you contract a muscle against resistance without actually shortening the muscle, creating a lot of muscle activity with no actual movement of the joint.
Our muscles play different roles and can generally be described as stabilizers or mobilizers - this is based on the type of muscle fibres that make up that particular muscle. There are 3 types of fibres, and muscles contain a mix of all three:
1. Slow twitch (Type I)
2. Fast twitch (Type IIa)
3. Fast twitch (Type IIb)
Muscles containing a high percentage of slow twitch fibres effectively use oxygen to generate a contraction - these are your stabilizers. They can sustain long periods of activity and are slower to fatigue. These include the muscles that control your core and posture.
Fast twitch fibres are not effective at using oxygen - these are your mobilizers. They can produce a quick burst and powerful contraction, but fatigue very quickly. These muscles include the ones you'd use to jump, punch or sprint.
The composition of fibres in each of your muscles is genetic but can be changed through training. Slow twitch fibres can morph into fast twitch and vice versa depending on your sport, daily activities, and how you use a specific muscle. This explains why sprinters don't run marathons.
So... why don't I prescribe isometric neck exercises to my patients?
Because the muscles in the neck are postural, meaning they are marathoners, primarily composed of slow twitch fibres; it doesn't make sense to train them like sprinters. Isometric exercises are more suitable to train fast-twitch muscles, and while they can also be used for stability - these types of exercises are not specific to how we use our neck. Day-to-day, most of the load the neck sustains is against gravity, so this is where your rehabilitation should be focused.
Recommended exercises coming soon!