Impact of Finger Position on Pinch Strength

Research Article

Phys Med Rehabil Int. 2017; 4(1): 1108.

Impact of Finger Position on Pinch Strength?

Walukonis KR¹*, Beasley J², Powers J³, Boerema R4 and Anderson K5

¹Special Education Department, Traverse Bay Area Intermediate School District, USA

²Department of Occupational Therapy, Grand Valley State University, USA

³Special Education Department, Wexford-Missaukee Intermediate School District, USA

4Rehabilitation Department, Cottage Rehabilitation Hospital, USA

5Department of Statistics, Grand Valley State University, USA

*Corresponding author: Walukonis KR, Special Education Department, Traverse Bay Intermediate School District, 1101 Red Dr., Traverse City, MI 49684, USA

Received: January 18, 2017; Accepted: February 10, 2017; Published: February 13, 2017


Pinch strength is a widely used measurement of hand function, but digit position on the pinch gauge has not been described in the literature. The aim of this study was to assess for differences in tip, lateral and three-jaw-chuck pinch force when the digits are placed on the groove or bridge of a B&L pinch gauge. Thirty-six healthy volunteers each pinched six times in random order: one for each type of pinch force with the digits placed in each position. There were no significant differences in pinch strength measurements based on digit position. Equivalence was found within one pound for tip and lateral pinch. Variations in finger position may result in similar pinch strength measurements for tip and lateral pinch. Clinicians may reliably assess lateral and tip pinch using either position; however, standardized positioning is still recommended.

Keywords: Strength; Positioning; Gauge; Bridge; Groove; Pinch


B&L: Bernadette and Linda; ASHT: The American Society of Hand Therapists; IP: Interphalangeal; SPSS: Statistical Package for the Social Sciences


Pinch strength measurement is a key point of interest to a myriad of health professionals working in hand therapy. A direct relationship between pinch strength and function has been demonstrated and illustrates the importance of hand strength in clinical practice [1- 2]. Clinicians, especially those interested in preventing deformities and preserving functional performance, utilize pinch strength as an assessment tool and outcome measure. Specifically, pinch strength measurement using the “gold standard” Bernadette and Linda (B&L) pinch gauge has been found to be psychometrically sound with established reliability and validity [3,4]. Clinicians and researchers utilize pinch strength to compare clients’ strength with normative standards, characterize upper extremity impairment, document improvement in strength and overall function, determine goals, demonstrate industry research outcomes, and provide appropriate interventions [1-6].

Position of the upper extremity during hand strength measurement has been a topic of discussion for decades. In 1981, The American Society of Hand Therapists’ (ASHT) suggested norms for arm position during grip strength tests [7]. Fess and Moran recommended, “the patient should be seated with his shoulder adducted and neutrally rotated, the elbow flexed to 90°, and the forearm and wrist in neutral position” [7]. However, while these recommendations may be valuable, they do not necessarily provide a standard testing position specific to pinch strength. A measurement protocol specific to pinch strength was not included in the ASHT recommendations, nor has it been established in the literature thus far. Several studies have addressed the impact of certain factors on pinch strength as well as provided recommendations for standardizing pinch strength positioning independent of grip strength; however, positioning the finger on the bridge or the groove of the pinch gauge has not been carefully described. Therefore, additional normative studies specific to hand and forearm positioning are needed to establish a comprehensive standard measurement protocol for the assessment of pinch strength.

One two-part study addressed the effect of various upper extremities positioning on pinch strength with 20 healthy male students aged 20 to 34 years [8]. Results indicated no effect of shoulder position on pinch strength measurements, but a large effect of elbow position on pinch strength measurements when the elbow was flexed 120 degrees or more. Secondly, Halpern and Fernandez examined forearm and wrist positions [8]. This experiment included 27 combinations involving three different pinches (lateral, tip, and three-jaw-chuck), three forearm positions, and three wrist positions. Results of this study indicated that for all three types of pinch combined, maximum flexion and extension of the wrist resulted in decreased pinch strength measurements. The pronated forearm position also showed decreased pinch strength measurements (up to 7%), as compared with supinated and neutral forearm positions.

Stegink Jansen and colleagues researched the effect of three forearm positions on lateral, tip, and three-jaw-chuck pinch measurements [9]. This study agreed with an earlier study by Woody and Mathiowetz, which found that forearm position, did not affect three-jaw-chuck pinch measurements [9-10]. However, unlike those researchers as well as Halpern and Fernandez, Stegink Jansen and her colleagues found differences in lateral and tip pinch measurements between the different forearm positions [8-10]. They found measurements of lateral pinch to be lowest in the supinated position, while tip pinch measurements were lowest when the forearm was pronated. Although these differences were noted, none of the differences were found to be statistically significant (largest effect size .144). The researchers used these findings to suggest that “standardization of forearm position is recommended when measuring pinch strength, but not required” [9].

They also suggested that the lack of standardization regarding finger placement on the bridge or groove of a B&L pinch gauge, could be a confounding factor when interpreting results of current, recent, and future studies.

Although little research has been done on the effect of finger position on pinch strength measurements, two studies have addressed factors specific to the hand. In one study, McCoy and Dekerlegand addressed the lack of standardization for positioning of the ulnar three digits during tip pinch with 76 healthy volunteers [11]. They found

that pinch strengths were larger when the fingers were flexed, which agreed with findings by Hook and Stanley [12]. These researchers suggested that lack of standardization could greatly impact pinch strength measurements because the values are small, so even small differences could largely impact pinch measurement scores. In another study, Apfel sought to determine if thumb interphalangeal (IP) joint position, flexed or extended, effects lateral pinch measurements [13]. This study examined two IP joint positions, flexed or extended. Findings included significant differences in pinch strength measurements depending on IP joint position when all ASHT positioning standards were followed. For females and males, IP joint flexion showed an increase in strength by 28-30% and 36-38% respectively as compared to IP joint extension measurements.

Currently, no studies in the literature have focused how finger and thumb positioning on the pinch gauge impacts pinch strength. The potential problem may be due to how clinicians guide clients to place fingers and the thumb on the pinch gauge versus calibration standards of the pinch gauge. B&L Engineering pinch gauges are calibrated with a digital force gauge by placing the pinch gauge into the force gauge at the groove. Therefore, the owner of B&L, Lee Barnes, recommends that clients place fingers on the groove of the pinch gauge (Figure 1) when taking pinch measurements. Regardless of this recommendation, many clinicians feel that placing fingers and the thumb on the bridge of the gauge (Figure 2) is a more natural position. There were no studies found specifying the area of contact between the tip of the finger and thumb, but authors who presented illustrations of the test position showed that subjects pressed the bridge of the pinch meter rather than the groove [9]. The current study sought to determine if this discrepancy is clinically relevant and potentially introduce finger positioning recommendations.