I wanted to get my thoughts straight on this topic and thought it would be good to have a collaborative stab at this to provide a practical guide that doesn’t get too bogged down.
Below is a draft off the top of my head and I’ll edit the text as the thread develops so we can arrive at a current consensus:
The strength in your fingers are mainly generated by the muscles in your forearms which are called flexors. There are two flexors for each finger. Each flexor is anchored at the elbow by a tendon and attached to a finger via a tendon which is kept in place through the fingers by tendon sheaths and five ring shaped pulleys in each finger.
The types of finger strength climbers are mainly interested in are isometric where there is no movement in the fingers ie flexors are under tension but don’t shorten. There are some situations where concentric/eccentric movement is applied such as turning a an open grip into a crimp but regular training of this under load is inadvisable due to the see saw action of tendons against the pulleys.
There are two types of muscle fibre that make up the flexor - fast twitch and slow twitch muscle fibres. Slow twitch fibres (Type 1) are weaker and need oxygen but can produce force for a long time. The fast twitch fibres, of which there are two types: 2a and 2b, are stronger and work mostly without oxygen. Type 2a fibres can produce high level of force for about two minutes and Type 2b fibres, which are the strongest, last for about ten seconds.
However, you can become stronger by making the individual fibres bigger (hypertrophy). Just over half of the variance in strength between individuals can be explained by their muscle size.
The other main trainable determinants of strength are tendon stiffness (a stiff tendon transmit more force from muscle the contractions to the limbs), coordination between muscles, how large proportion of the muscle is recruited, the rate at which signals to muscles are sent, and specific tension (the ability to transfer strength through a muscle).
The complicated energy systems supplying the muscles and flushing out waste products also play a part especially with finger endurance which is very trainable. Finally the stiffer your tendon the quicker you can apply force to a hold because of the reduced stretching (however it’s thought that stiffer tendons lead to a greater risk of injury).
These are the main types of finger strength
Rate of force development / Explosive strength This is the power component - how quickly you can apply force when for example latching a hold dynamically
Peak/Maximal force This is the maximum amount of force you achieve during any given hang
Strength Endurance Not strictly strength but how you can apply force under different levels of fatigue, during long hangs or after incomplete rest.
Below are the main types of fingerboard exercises:
Max hangs: Hanging at your limit provides major stimulus for both neural development and hypertrophy. Downside is that it requires a lot of recovery time.
Sub Max hangs: As above but less stimulus and can be done more often
Recruitment pulls: Also called overcoming isometrics. With this you apply full force for the duration of the hang whilst feet remain on the ground to train force development when pulling on a hold often combined with the next exercise
Speed pulls / Velocity hangs: Short and intense with the main impact to improve the speed of muscle recruitment and increase tendon stiffness to reduce the time to generate high force (ie improving contact strength to latch a hold)
Density hangs: Long duration hangs promotes hypertrophy and increases the density of connective tissue for injury prevention purposes. Reduces tendon stiffness
Repeaters: Trains strength endurance
Other factors
Grip types: Finger strength proportionally varies between individuals (sometimes dramatically) depending on grip type. There are three main types of grip when using all four fingers on a fingerboard: Full crimp, half crimp and drag. The half crimp is thought to be the best overall training grip as there is more training crossover to full crimp and drag. However, ideally all grip types should be trained as well as deployed when climbing
Antagonists
Sometimes strength development is held back by weak antagonists. With the fingers this would be the extensors. Standard extensor training is normal and reverse dumbbell wrist curls. There seems to be a big market for alternative gizmos.
