By Adam Scott, MS, CSCS
Grip strength testing has become increasingly popular for tactical professionals. Whether it is directly assessed using a dynamometer or indirectly measured during weighted pull-ups, dummy drags, ammo can carries, farmer’s carriers, or the likes – grip strength has become a major part of the tactical athlete’s testing battery.
Why grip strength matters…or possibly doesn’t
In the general population, grip strength has been reported to be a predictor of numerous forms of muscular strength – including both upper and lower body absolute muscular strength and muscular endurance (6).
Because of its correlation to overall strength, grip strength is a popular measurement in elderly and diseased populations (10). Many studies have shown that grip strength can be a long-term predictor of “all-cause mortality” – especially cardiovascular disease and cancer (4).
However, when it comes to athletic performance, handgrip strength measures are more of a mixed bag.
One studying, looking at handgrip dynamometer strength and bat speed in collegiate baseball players found that improvements in grip strength had no impact on bat speed or batting performance (3).
On the other hand, in a sport which has virtually no grip element, swimming, a 2008 Italian study, found that hand dynamometer grip strength could be used to predict swimming performances in elite master swimmers (r=-0.46 to r=-0.76, p<.05) (9).
Research from Australia and New Zealand examining strongman competitive performances found that farmer’s carry grip strength was the least predictive measure of overall strongman performance at r=0.69, p<.05 (7). The most predictive measure of overall performance was tire flip ability, at r=0.88, p<.05 (7). Additionally, flexed-arm girth (but not grip strength) demonstrated the highest anthropomorphic interrelationship with strongman competitive performance (r=0.79, p<.05) (7).
Of all the available research, the sport of judo has possibly given grip strength the most attention. One study, looking at elite and sub-elite judo competitors found that elite judokas had higher arm muscle mass than their sub-elite counterparts. However, the study found no significant difference between elite and sub-elite judokas handgrip strength (1). This finding has been supported by multiple additional studies (11,16).
On the tactical side, despite the increased popularity of grip strength testing, there is very little research into its relationship to tactical performance. A 2004 study from Arizona State University found that grip strength was the third highest fitness-related predictor of Firefighter job performance ability (behind 400m sprint and bench press endurance)(2). And, a 2001 study from the Police Training Institute at the University of Illinois, in Champaign, Illinois found that grips strength might have a small effect on marksmanship scores in police recruits (13). However, there were a number of other confounding factors.
Clearly, there is some level of grip strength demand inherent to each tactical profession. This seems especially true during selections and assessments, which tend to use endurance-based grip demands to challenge their candidates. There are also many tactical job tasks which require grip – handling suspects, hoisting ladders, climbing ropes, etc. – however to what degree grip strength and/or grip strength training is required has yet to be determined.
Until such standards are established and understood, perhaps the place where grip strength assessments might be most useful is as a measure of tactical athlete recovery, not ability. There is a growing catalog of research which shows that pre-training grip strength can be used as a measure of athlete recovery and training ability (13). One such study recommends that athletes who fail to reach within 2kg of their maximum scores are not neurologically recovered from their previous training session(s) (13).
In the end, grip strength likely plays some role in tactical performance, but exactly what that role is or how important a role has yet to be established. However, since tactical grip strength testing seems to be here to stay, we decided to try and answer two important questions…
- What are the Major Differences in Grip Strength Testing?
- What Types of Testing and Training is recommended?
…Unfortunately, there are still many more questions left unanswered.
What are the Major Differences in Grip Strength Testing?
Although there are many variations, most grip strength tests can be divided into two categories:
A. Strength – a single, dynamic “squeeze” tests using a handheld grip strength dynamometer to measure the muscular force generated by flexing the hand and forearm (12).
B. Strength Endurance – a static, isometric “hold” typically measured in time or, if used in a carry, distance. These tests require an athlete to maintain a certain amount of force (using a dynamometer) or hold a certain load (pounds or kilograms).
Although both tests are often referred to as “grip strength tests” they are actually extremely different – as different as testing 1RM bench press and 2-minute push-ups. Since we couldn’t find any research comparing the two grip measurements we decided to test them with our local athletes.
Subjects: 13 male and 4 female athletes completed three grip assessments. Male average age was 34.6 (+/-6.2) years; average height was 72.1 (+/-2.4) inches; and average weight was 181.8 (+/-15.4) pounds. Female average age was 33.5 (+/-1.9) years; average height was 65.5 (+/-4.1) inches; and weight was 137.5 (+/- 21.6) pounds.
A. Farmer’s Carry for time (Females used 2x55lb Kettlebell and males used 2x70lb Kettlebells): For this test athletes were required to maintain constant movement while holding the weight by their sides. The distance covered did not matter, only the time they could hold the weight
B. Towel Pull-Ups: A full-sized towel (27”x58”) was folded into thirds and draped across a pull-up bar. Athletes grasped the outside of the towel and were not allowed to overlap their hands. Starting from a dead hang position, the athletes completed as many pull-ups as possible while grasping only the towel.
Results: Based on our study there was no significant correlation between the three tests. In males the only measurements which had significant correlations to grip test results were: Height and Towel Pull-Ups (r=-0.77, p<.05), Weight to Towel Pull-Ups (r=-0.56, p<.05) and Weight to Dynamometer (r=0.74, p<.05).
In females, no measure had a significant correlation to Towel Pull-Ups or Farmer’s Carry. However, Dynamometer strength was significantly correlated to Age (r=-0.99, p<.05), Height (r=0.98, p<.05) and Weight (r=0.91, p<.05).
** Statistically Significant p < 0.05
Discussion: The finding that these three grip measurements (Farmer’s Carry, Towel Pull-Ups, and Dynamometer) showed no significant relationship was somewhat surprising. Although previous research has delivered mixed results, many studies have shown a relatively strong relationship between muscular endurance tests and maximum strength tests (13-15). So, using the previous example of 1RM bench press and 2-min push-ups we expected at least some measurable relationship between the tests (13,14).
It should be pointed out that, while in males the relationships were especially weak, the correlation between a few of the female tests were stronger. However, because we had such a low number of females the standard for statistical significance was extremely high.
Another interesting finding was that towel hang pull-ups had a negative correlation with dynamometer strength (second row of table) – meaning that decreases in towel pull-ups were related to increases in dynamometer strength.Basically what this small study showed us was that “grip strength tests” are extremely specific. A high dynamometer score (single squeeze strength) will likely have little or no impact on an athlete’s ability to carry loads for time (grip endurance). We also found that grip type (solid metal vs. cloth) will greatly impact grip performance and, again, there is virtually no carry over between the two varieties.
What Types of Testing and Training is recommended?
When selecting a test it is vital that assessments be designed with specific attention paid to the actual demands – strength or strength endurance; small grip or large grip; metal bar or cloth; etc. As previously stated there is little to no carry-over between most grip strength assessments. Therefore, the test should, as closely as possible, mimic the actual demands which are required.Also, when it comes to training for grip strength it is vital that an athlete train sport specifically for the improvement they are seeking. In our most recent cycle, athletes trained grip endurance using the farmer’s carry and towel hang pull-ups mentioned above. Athletes completed 3 grip circuits 3 times a week as part of their regular training. Although the cycle only lasted 4 weeks, during our post-test assessment it was clear that our grip training has very little effect on our athlete’s dynamometer grip strength.Of the 17 individuals who participated in the testing and training, 5 actually experienced decreases in their dynamometer grip strength while they increased their farmer’s carry and maintained their towel pull-up scores. Overall, all 17 subjects averaged only an insignificant increase (based on paired T-Test analysis, p>0.60) in dynamometer strength: 5.8% despite near significant increases in both farmer’s carry and towel pull-ups.So, without getting too into the weeds…if you want to improve your dynamometer (flexion/squeeze) strength you need to train resisted flexion (using Grippers or similar devices). If you want to improve your grip endurance then you need to train holding heavy items (of similar size, type, and weight).
Either way, although it might help you pass a selection or testing, there is very little evidence showing that it will help you be a better operator.
- Drid, P., Casals, C., Mekix, A., Radjo, I., Stojanovic, M. and Ostojic, S. Fitness and anthropometric profiles of international vs. national judo medalists in half-heavyweight category. J Str. Cond. Res. 29(8): 2115-2121. 2015.
- Rhea, M., Alvar, B. and Gray, R. Physical Fitness and Job Performance of Firefighters. J Str. Cond. Res. 18(2): 348-352. 2004.
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