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Every year as the season subsides coaches start to ask “what could we have done better or different.”. This helps us prepare for the additional things or changes that need to occur in the following year. Three things that are consistently evolving in our industry are testing, programming and data analysis. While technological advances in ways to measure performance variables are quickly evolving, there is always the challenge of how to validate new testing tools that may not have adequate science them. Similarly, some forms of new technology are expensive and thus limit their use to a relatively small number of teams. Likewise, some forms of new technology are so complicated and time consuming that they are difficult to use in high-volume, practical settings. Therefore, selecting appropriate testing tools and protocols can be tricky as coaches strive to obtain the most reliable, valid and useful data. For this reason, I would like to recommend a reliable and valid testing tool, the hand grip dynamometer, and recommend a few things to consider during grip strength testing.

There are a number of good reasons to consider grip strength testing as one of your standard tools of choice. For one, the hand grip dynameter’s reliability and validity as a testing device have been documented in several scientific publications. Research, for example, indicates that grip strength weakness can be an indicator of upper extremity injury pathology2. Data suggest that a weak grip strength reading can be a stronger marker of weakness than chronological age3. Population studies have yielded grip strength norms among males in the age ranges typically seen in minor league players6. These normative values are presented in the following table.

 

Table 1. Grip strength norms for males ages 16-29
  Right hand Left hand
Age Mean (lb) SD (lb) Mean (lb) SD (lb)
16-17 94 19.4 78.5 19.1
18-19 108 24.6 93.0 27.8
20-24 121 20.6 104.5 21.8
25-29 120 23.0 110.5 16.2

 

Testing protocol. While grip strength is a highly utilized test in many organizations starting as early as instructional league and continuing throughout the season, a standardized protocol should be in place to ensure that every coach in the organization administers the test in a consistent manner to ensure that the results are reliable, valid and applicable from level-to-level and team-to-team. Some of the testing procedures that need to be standardized, for example include the angle of the elbow (flexed or extended), number of test trials permitted, posture (seated or standing), duration of the grip squeeze, time that the test is administered (AM or PM), when the test is administered (before practice, after practice, before game, after game, on off-day), how often and when is the test administered, etc. Any of the aforementioned variables can affect test results, skew the data and limit its usefulness.

The angle of the elbow during testing, for example, has been examined in several research studies. Early studies suggested the elbow should be flexed to 90-degrees in order to achieve max values. Recent research, however, suggests that the arm should be extended to achieve maximum values3.

Application of results. Once you obtain the data, what can you do with it? One option is to evaluate status periodically throughout the season to identify significant increases or decreases in grip strength. A significant increase might indicate the effectiveness of a specific training program or recovery from an injury. A significant decrease might indicate the ineffectiveness of a program, effects of an acute or chronic injury, incomplete recovery from an injury or effects of acute or chronic fatigue.

One method of data utilization is to calculate a grip strength index in which the index is the sum of the right- and left-hand grip measurements divided by body weight.

HG Index= (Right + Left) / Body weight

 

For scoring purposes, an athlete that exhibits an index less than 1.0 is someone that might be identified as a candidate for closer observation. Scores below 1.0 have been recorded in individuals who have an injury and/or need more strength. The index can also be used to help identify acute and chronic fatigue at various intervals during the season and identify strength gains, especially among younger players with little resistance training experience.

In conclusion, grip strength testing has been shown to be a useful tool especially with throwing athletes. It can help identify strength, weakness and in some cases injury. In order for the results of this test to be beneficial, however, it must be performed in a consistent manner. Having a written, standardized protocol will help ensure that every test is administered in a consistent manner that will ensure that the results are reliable, valid and meaningful. Gathering and utilizing test data periodically is an effective way to evaluate status, identify weakness or injury and help athletes achieve their performance goals.

References:

  1. Goldman S., et.al. The injured upper extremity and the JAMAR five-handle position grip test. Am J Phys Medi & Rehab, 70(6): 306-308, 1991.

 

  1. Sella, GE. The hand grip: gender, dominance and age considerations. Eur Med Phys, 37: 161-170, 2001.

 

  1. España-Romero, V. et.al. Elbow Position Affects Handgrip Strength in Adolescents: Validity and Reliability of Jamar, DynEx, and TKK Dynamometers

 

  1. Petersen, P. et.al. Grip Strength and Hand Dominance: Challenging the 10% Rule. J Strength Cond Res. 24(1): 272-277, 2010.

 

  1. Syddall, H., et. al. Is grip strength a useful single marker of frailty? Age and Ageing, Am J Occup Therapy, 43:444-447, 1989 32(6): 650–656,2003.

 

  1. Normative Grip Strength Data, Jamar Plus Digital Hand Dynamometer Grip Strength Instruction Manual, pg 11

 

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Orlando Crance, MA, RSCC, CSCS, USAW-SP, USATF-L1, is the Strength and Conditioning Coach for the Philadelphia Phillies Gulf Coast League West Phillies in Clearwater, FL.

 

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