As climbers, the strength of our hands and fingers is undoubtedly one of our most valuable tools. It allows us to hold onto holds, progress up the wall, and ultimately achieve our goals. But how do we really measure this strength objectively and accurately? Are we training effectively if we don’t know our starting point or our progress? In this post, we’ll break down the importance of grip strength assessment, the factors that influence it, and the best practices for evaluating it—transforming our sensations into concrete data and our training into applied science.

What is the ability to hold onto holds?

The ability to hold onto holds is defined as the skill to apply force with the finger flexors during complex body movements in stable equilibrium positions. It’s important to differentiate it from RFD (Rate of Force Development), which is the ability to generate force quickly in a dynamic balance. Here, we focus on the ability to maintain our weight (or part of it) on a hold in a stable context.

This ability does not depend exclusively on maximum isometric finger strength (MIFS), but on a complex interaction of factors.

The multiple factors influencing your grip

Grip strength is a network of elements working together:

Neuromuscular Factors: Includes the force generated by muscle activation and coordination.
Intrinsic Factors of the Hand-Fingers-Forearm Complex:
- Tendon compression mechanisms.
- Quadriga effect.
- Passive force components, such as titin filaments.
Extrinsic Factors:
- Friction coefficient between fingers and hold.
- Hand and finger size relative to the grip.
- Thickness of the finger pads (especially relevant on holds smaller than 6 mm).
- Condition and characteristics of the skin (hardness, viscoelasticity, moisture).

Although all these factors are important, the magnitude of the force we can express remains the most decisive factor.

The challenge of measuring grip strength specifically and validly

To effectively assess grip strength, it’s crucial that methods are climbing-specific and scientifically valid. Manual dynamometry, for example, is not specific to climbing and does not correlate with performance in this sport. Climbers apply force on small holds in a unique way that other athletes cannot replicate, so our tests must reflect those demands.

To achieve this balance between specificity and validity, we must carefully control several factors in test design:

Measurement duration.
Type and size of the hold used.
Execution method (PIMA or HIMA).
Whether the test is performed with one or two arms.

Measurement duration: peak force or sustained?

To reach maximum muscle tension, time is needed; maximum force cannot be generated instantly. Historically, maximum force was measured with 5-second (MAW_5) or 3-second (MAW_3) hangs. However, the introduction of force sensors has simplified the process and led to the adoption of peak force (PF) as a reference.

Peak force represents the maximum force that can be generated in an instant, without time constraints. There is a close correlation between peak force and the ability to maintain submaximal force levels for 3 or 5 seconds. In fact, it is estimated that maximum force measured at 3 seconds represents about 95% of peak force (PF), and at 5 seconds between 92% and 95%. Therefore, peak force is the preferred measure in current scientific literature. If a sensor is not available, 3-second weighted hang measurements (MAW_3) remain reliable and valid, with the relationship MAW_3 ≈ 95% * PF(HIMA).

The perfect grip: type and size

Grip choice is crucial and influenced by contact surface and climber experience. Isometric strength is expressed specifically in the joint range in which it has been trained.

Grip Type: According to the literature, the half crimp (90º flexion at the PIP joint) best differentiates climber levels. However, it is recommended to let the subject use their most comfortable 4-finger grip (open or closed) to express their real adaptations. The 4-finger grip is prioritized for safety, avoiding the full crimp (with thumb) to protect pulleys and lumbricals (quadriga effect). For assessments, the focus is usually on half crimp and half open.
Grip Size: The current trend is to standardize on 23 mm edges with a 12 mm bevel. However, high-level climbers often adapt to smaller holds, and evaluating them allows for more precise measurement of the flexor digitorum profundus (FDP), crucial in high-difficulty climbing. The key is to adapt the hold size to the climber’s level: a hold too large for an advanced athlete could underestimate their strength, while one too small for a beginner could be unsafe and less reliable.
- Bergua’s Proposal (2018): Assess on an edge where body weight represents about 75% of maximum force.
  - For intermediate or advanced climbers: a hold where they can hang for 40 seconds to failure (MED_40).
  - For explosive-profile climbers (boulder/sport, less trained): a hold where they can hang for 25 seconds to failure (MED_25).
  - For beginners: a max time to failure test on 14 mm.
- MED_40 can be estimated from max hang time on a 16 mm edge (MHT_16).

Execution: PIMA or HIMA

Two types of isometric contractions are distinguished:

PIMA (Pulling/Pushing Isometric Muscle Action): Measures the ability to generate muscular tension actively and purely contractile, isolating the forearm muscles.
HIMA (Holding/Yielding Isometric Muscle Action): Also involves a series of passive structures (tendons, ligaments) that add to the expressed force.

Studies indicate that PIMA may offer greater reliability in reproducibility, but HIMA shows greater specificity and correlation with climbing performance (construct validity). Therefore, HIMA execution is recommended for maximum grip strength assessment. Evaluating both can be useful for detecting bilateral deficits or responses to specific training, although PIMA requires specialized equipment.

Unilateral or bilateral: do we measure with one or two hands?

Unilateral (one hand) assessment with force sensors is valuable for injury prevention, as greater strength asymmetry between sides is associated with higher risk. Climbers tend to have less asymmetry (3–5%) than the general population (10%) due to the bilateral nature of the sport.

Interestingly, in climbers, the force applied in a bilateral hang tends to be greater than the sum of unilateral forces. This could be explained by greater joint stability of the shoulder girdle in bilateral execution. However, unilateral assessment gives us crucial information about possible deficits and underlying issues in the upper limb kinetic chain.

Proposed protocol for maximum isometric strength assessment (Bergua 2023)

Selection of adjusted edge size: Use MED_40 or MED_25 according to profile, or MHT_16 to estimate.
Unilateral peak force (PF) assessment: With the HIMA method, emphasizing dropping weight onto the hold.
Optional PIMA assessment: To compare active and passive force.
Calculation of the Strength Indicator:
- Indicator = (Peak Force * 0.95) / (Body Weight * Edge Size).
- This 0.95 factor normalizes peak force to a value more representative of sustained force at 3–5 seconds, the most studied.
- Typical ranges: <7a (<5), 7a–8a (5–10), >8a (10–20).

Although this methodology is based on personal observations and not scientifically validated, it has shown greater validity than studies using only one edge size.

Considerations for different levels and special cases

Beginner Climbers: Simpler and safer tests, such as max hang time on a moderate edge (16 mm or the size of the distal phalanx) or determining the edge size for a fixed hang of 25–40 seconds.
Subjects with Short Pinky: Measurement can be done with the three central fingers, using syndactyly taping (joining pinky and ring finger) to prevent injuries and avoid the quadriga effect.

Conclusion

Grip strength assessment is a fundamental pillar for intelligent climbing training. It allows us to go beyond perceptions, obtaining precise and reliable data that guide our progression. By considering grip type, size adjusted to our level, duration and execution method, and whether we measure unilaterally or bilaterally, we can get a clear picture of our capacity. Thus, we transform “feeling” into “knowing,” optimizing our training and climbing with greater efficiency and safety.

The Science Behind Measuring Your Grip Strength