Hand grip and what it means for a long, healthy life.

Hello Everyone!

Welcome to another edition of the monthly 'Amuse-Bouche' series. Like a morsel compliments of the chef, these small but critical scientific bites are created to stimulate your thinking about health and occasionally provide some comic relief. Prior editions.

Talk to the Hand

We all want to get a grip. Yet a grip is not really about the hand. The hand itself contains almost none of the muscle that produces crushing force and fingers have no muscles in them at all.

A seemingly simple measure, our grip strength surprisingly reflects the integration of muscle, nerves, nutrition, cardiovascular fitness, and habitual physical activity.

In the PURE study published in the Lancet in 2015, which followed nearly 140,000 adults across 17 countries, every 5-kilogram (~11 lb) decrease in grip strength was associated with a 16% increase in all-cause mortality and a 17% increase in cardiovascular mortality. What was astonishing was that grip strength predicted these outcomes better than systolic blood pressure.

Consequently, testing grip strength using a simple tool called a grip dynamometer is becoming a routine clinical screening tool. I do this with patients in my practice every day.

What is grip strength?

Grip strength is the force with which a person can hold or squeeze an object with their hand.

Grip strength peaks in our 30s to early 40s, plateaus, and then declines after age 50. People who maintain their grip strength tend to stay healthier longer and maintain higher strength levels.

Grip strength has an important role in daily life and in many sports, like gymnastics, rock climbing, baseball, tennis and martial arts, where one is gripping objects or opponents. Clinicians also use grip strength diagnostically after medical events or procedures such as a stroke or hand surgery, where it can indicate the level of damage or recovery.

Grip is also used to screen for sarcopenia, which is the abnormal loss of skeletal muscle mass, strength, and function. This is distinct from normal age-related muscle loss and seen increasingly in patients who use GLP-1 medications but are not able to maintain adequate protein intake and/or resistance training. The term comes from the Greek sarx (flesh) and penia (loss).

The European sarcopenia consensus used grip strength cut-offs of <27 kg for men and <16 kg for women for probable sarcopenia, although normative values do vary with age. The attached table provides a range, and numbers lower than these should trigger further clinical evaluation.

Types of grip

Crush grip is gripping by closing the fingers around an object and driving them toward the palm; it is related to the clamp grip, in which the fingers are driven toward the base of the palm, and the crimp grip, in which the fingers remain near the top of the palm. Crush (power) grip is dominated by the forearm flexor muscles with nerve supply from the median and ulnar nerves. Functionally: handshakes, opening jars, gripping a hammer or barbell.

Pinch grip is the action of gripping an object between the fingers and the thumb. Pinch grip depends heavily on the intrinsic hand muscles. Clinicians subdivide it further: two-point (tip) pinch, lateral (key) pinch, and three-point (three-jaw chuck) pinch. Functionally: turning keys, buttoning shirts, handling small objects - this is the grip most relevant to fine-motor independence, and it's disproportionately affected by thumb arthritis, carpal tunnel syndrome, and ulnar neuropathy.

Support grip refers to the ability to hold an object for a long period of time while the fingers bear the brunt of the weight, as when holding a bucket by the handle. Support grip is isometric endurance rather than peak force - holding on over time. Functionally: carrying groceries, holding a railing, farmer's carries. It reflects muscular endurance and fatigue resistance, a physiologically distinct quality from maximal force.

All-Out Crush Grip

While not involved in most gripping activities, crushing grip is by far the most tested type of grip strength in research, due to the ease of use of grip dynamometers.

PURE, UK Biobank, and much of the prognostic literature use a single quantity: a one-time, few-second, all-out squeeze or peak isometric force production.

Where grip strength is created

The prime movers of a crush grip are the extrinsic flexors sitting in the forearm: large, thick muscle bellies whose long tendons run down through the carpal tunnel and insert on the finger bones. When we squeeze a dynamometer, we are contracting our forearm muscles to generate the force while the hand delivers it.

This is an elegant engineering solution: by locating the motors remotely and transmitting force by cable (tendon), the hand stays light, slender, and fast while still accessing the power of much larger muscles. If the muscles needed to generate 40–50 kg of grip force lived inside the hand, the hand would be the size of a club and useless for fine work.

The forearms and trunk (core) generate power and stability proximally (close to the body) and precision executed distally (further from the body) with the hands. If we don’t use our core correctly, we create shoulder and arm injuries because we try to generate force or exercise using the smaller, distal muscles.

Roughly 35 muscles of the forearm and hand participate in gripping, with the small intrinsic muscles (interossei, lumbricals, thenar and hypothenar groups) acting as stabilizers and fine-tuners — positioning the fingers, balancing the flexor pull, and preventing the joints from collapsing under the load the big forearm muscles deliver. The smaller muscles contribute more to the pinch grip than the crush grip.

Chain of command

Brain initiates a maximal grip effort: one of the most complete voluntary activations the entire nervous system performs.

Force scales two ways: recruiting more muscles and increasing their firing rate. Grip reflects recruitment more than firing rate.

Force multiplier: the forearm flexors are pennate muscles - fibers angled against the tendon like barbs of a feather – a design that packs more contractile fibers into the same volume at the cost of speed. Muscle force scales with physiological cross-sectional area (~25–35 N per cm²), so pennation builds force in a compact compartment.

Grip force depends critically on wrist position: maximum crush force occurs with the wrist in roughly 20–35° of extension, because extension pre-tensions the finger flexor tendons to their optimal length on the length–tension curve. If the wrist is flexed, the grip strength collapses by 40–60%.

Tendon force amplification: biomechanical studies of finger flexor loading show tendons subjected to 2–4 times the force measured at the fingertip, because the tendons work at short lever arms around the finger joints. The system pays a mechanical-advantage penalty at the joints, which means the muscles and tendons are generating internal forces far larger than the number on the dynamometer. If there were no pulleys in the hand, the tendons would bow away from the fingers like a bowstring.

The kinetic chain - grip is a whole-body event

The kinetic chain idea: the body produces and transmits force as a linked system of segments, and force expressed in the hand depends on the stability of every link in that chain. The operating principle is proximal stability enables distal force production. The forearm flexors cannot pull hard against the fingers unless the wrist is stabilized by opposing extensor muscles (which fire simultaneously during a hard grip — a co-contraction we can detect by squeezing a fist and noting the tension in the forearm), the elbow is stabilized by the arm musculature, the shoulder is fixed against the torso by the rotator cuff, lats, and pecs, and the trunk is braced against the ground.

Two demonstrations can make this concrete:

Positional dependence. If we squeeze maximally with our arm braced at our side, then again with the arm floating overhead we can immediately tell the difference. The drop in perceived force is the kinetic chain in action - the same forearm muscles produce less usable force when their anchor, which is the core, is unstable.

Irradiation (concurrent activation potentiation). A maximal grip effort recruits muscles far up the chain automatically - activation of the forearm, biceps/triceps, shoulder, and core/trunk rises during hard squeezing. Neural drive overflows across the chain. The reverse also holds: whole-body tension augments grip, which is why strength athletes brace everything to lift.

What does crush-grip dynamometry NOT measure

A single maximal squeeze does not capture:

Muscle power or how fast force can be produced. This declines with age faster than peak strength and is more relevant to fall prevention (catching a fall requires rapid force, not maximal force). A high grip reading says nothing about power.

Muscular endurance. Support grip and fatigue resistance are separate qualities; two people with identical grip strength can differ enormously in how long they can sustain it.

Lower-body strength. Using chair-stand performance instead of grip strength more than doubled probable sarcopenia prevalence in the European Sarcopenia study. Someone can pass the grip test but have weak legs.

Muscle mass. The dynamometer reads force output, not tissue quantity; it is not a body-composition measurement.

Fine motor function and dexterity. Pinch strength, coordination, and hand function follow different anatomy (intrinsic muscles of the hand) and are tested with different tools. A stroke or neuropathy patient can retain crush force while losing usable hand function, and vice versa.

Cardiorespiratory fitness. The UK Biobank analysis of almost half a million participants examined grip strength and cardiorespiratory fitness as distinct modulators of the physical activity-mortality relationship - they are complementary indices.

Accuracy and reproducibility of measurement. Hand arthritis, injury, pain, and variable measurement protocols are some reasons why grip strength measurements might be inexact or uninterpretable.

Crosstalk

We consider the main role of skeletal muscle to be controlling body movements through the generation of force. But skeletal muscle is also our primary protein store and the main outlet for glucose disposal in our body - both crucial for a long and healthy life.

Moving muscles release myokines - hormone-like signaling proteins — into the bloodstream, acting like an endocrine organ. The idea is crosstalk: proposed myokine signals reach fat, liver (regulating glucose output), bone (shared loading signals), pancreas, immune cells, and brain (irisin, brain-derived neurotrophic factor or BDNF).

This is one of the explanations why exercise benefits nearly every organ system despite happening in only one of them - and, conversely, why inactivity is a disease multiplier. An unused muscle is wasted capital. A weak grip signals this wasted capital. Likely why hand grip strength links to so many body systems and outcomes.

Grip strength and quality of life

Loss of grip strength often precedes the loss of independence.

Before someone can no longer live alone, they stop opening jars, carrying groceries, lifting grandchildren, climbing stairs while carrying laundry, or getting themselves off the floor. Grip strength is one way to alert clinicians. Strength predicts health outcomes better than just mass, like an arm or calf circumference.

Improving grip at any age

The goal is to maximize strength and prevent loss after the 40s and 50s. If someone has low grip strength, they can improve nutrition, begin strength training and recheck their grip every 8-12 weeks.

The best way is full body exercises like carries, deadlifts, squats and resistance training 2–3x/week, along with eating adequate protein (1-1.5 grams/kg body weight daily).

Meat of the matter

In medicine, we measure grip strength because it is a vital sign of physiologic reserve. It represents independence, resilience, recovery from illness, and ultimately a healthy lifespan.

Talk to the hand!

 References:

1. Leong DP, et al. Prognostic value of grip strength: findings from the PURE study. The Lancet 2015;386:266–273. 

2. Celis-Morales CA, et al. Associations of grip strength with cardiovascular, respiratory, and cancer outcomes and all-cause mortality. BMJ 2018;361:k1651. 

3. Sayer AA, Kirkwood TBL. Grip strength and mortality: a biomarker of ageing? The Lancet 2015;386:226–227. 

4. Cruz-Jentoft AJ, et al. Sarcopenia: revised European consensus on definition and diagnosis (EWGSOP2). Age and Ageing 2019;48:16–31.

5. Ortega FB, et al. Muscular strength in male adolescents and premature death: cohort study of one million participants. BMJ 2012;345:e7279.

6. Cooper R, Kuh D, Hardy R. Objectively measured physical capability levels and mortality: systematic review and meta-analysis. BMJ 2010;341:c4467.

7. Esteban-Cornejo I, et al. (grip strength and dementia, UK Biobank). Journal of Cachexia, Sarcopenia and Muscle 2022;13:1514–1525.

8. Wu D, Gao X, Shi Y, Wang H, Wang W, Li Y, Zheng Z. Association between Handgrip Strength and the Systemic Immune-Inflammation Index: A Nationwide Study, NHANES 2011-2014. Int J Environ Res Public Health. 2022 Oct 20;19(20):13616. doi: 10.3390/ijerph192013616. PMID: 36294194; PMCID: PMC9603468.

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Proof of Life: Work along with Play

The garden has been blooming, and with that, the number of insects — especially bees — has increased exponentially. A native plant species can support upwards of 50 different bee species, compared to an ornamental, which can support about 15! I won't bore you with blurry pictures of insects flying around in my backyard, but I have to talk about a couple. The first is a bee on native coneflowers.

The second is a snake fly, a rare insect dating back to the Jurassic period — one that followed me into the bathroom from the garden. It was large and a bit scary. Sadly, I killed it in a panic with a copy of Entrepreneur magazine before I could identify it using AI. :(

Some of you may have noticed a longer gap in the Amuse-bouche articles this summer. It has been interesting to experience something akin to writer's block. After working very hard on these articles for a year — and even harder on the recent cholesterol and GLP-1 pieces — I felt considerably more pressure to maintain a high standard of writing. So much so that I felt unable to publish. I'm trying to come to terms with the fact that the act of writing and learning is more important than the quest for perfection. I can see why many writers get stuck in this futile self-flagellation instead of continuing to create.