Hand strength as determinants for container opening strategy in healthy adults

Objective: This study hypothesized that there would be a statistically significant difference in pinch and grip strengths depending on the strategy employed to open medicine bottle containers Method: Sixty six healthy participants (19 male and 47 female) from the community participated in this research study which examined strategies for opening small, medium, and large medicine containers through video recordings. Hand grasp and finger dynamometry were also obtained. Results: There was a significant difference between the lateral pinch and gross grasp when using the palm and hybrid bottle opening strategy for the large and small bottles. Specifically, there was a significant difference in lateral pinch for the large bottle, between the palm and hybrid strategies (p-value = .036), in gross grasp strength when using palm and hybrid strategies when opening the large bottle (p-value = .030), in lateral pinch when grasp using palm and hybrid opening the when opening the small bottle (pvalue = .007), and in gross grasp strength between palm and hybrid grasp strategies when opening the small bottle (p-value = .025). Conclusion: The results of the current study suggest the importance of educating clients about the use of proper joint protection techniques when opening medicine bottles and facilitating hand and finger strengthening occupations to increase daily task capabilities. Further research is needed with participants with compromised orthopedic or neurologically compromised hand function to determine the natural strategy for opening containers based upon strength. Strength Determinates 3 Introduction On a day to day basis, individuals engage in occupations, such as brushing teeth and donning clothing. In completing these tasks, people move in carefully coordinated actions that generally require functional use of the hand and fingers. A wide variety of movement patterns are influenced by hand and finger strength and size during an occupation. That is, the comprised kinematic and kinetic variables involved in the coordinated motions are often highly complex, although the specificity of the control most often occurs at the subconscious level. Due to the highly complicated nature of coordinated movements, any number of factors can interfere with the delivery of such coordination; for instance size and strength of the hand and fingers for someone with arthritis may limit function, and consequently, interrupt everyday occupations. It is also possible that wrist and hand injuries such as carpal tunnel and joint deformities (e.g., swan neck deformity) can prohibit someone from have sufficient range of motion needed in order to perform occupations. The objective of the current study is to investigate the association between hand and finger strength and the motor strategies during the act of opening medicine containers. Background A common daily task for many people is opening medicine containers for the purpose of retrieving medications and nutritional supplements. Proper hand function can help arbitrate personal drive towards something that has personal meaning and purpose. Reilly (1962) proposed that “man through the use of his hands, as they are energized by mind and will, can influence the state of his own health” (pg. 2). Therefore, a familiar Strength Determinates 4 practice by occupational therapists is to focus treatment on improving hand function by encouraging strength and coordination for the purpose of improving task aptitude. Before an occupational therapist can begin treating in order to improve hand dysfunction, they must first assess the individual’s current function. Functional evaluation tests are one way an occupational therapist can assess hand performance. McPhee (1987) studied the validity of 11 different hand evaluations, some of which included Jebson’s Hand Function Test, MacBain’s Hand Function Test, Potvin’s Activities of Daily Living Examination, and the Nine Hole Peg Test. McPhee found that 82% of the 11 tests used time to measure for hand function, and 55% of the assessments tested bilateral hand use. Unfortunately, time and unilateral determinates, according to McPhee, are not exclusively accurate portrayals of hand use. Therefore, McPhee concluded that the therapist should assess a patient using several hand tests to compensate for the fact that individual tests lack clear meaning and fail to be comprehensive. Furthermore, functional hand tests should be synchronized with an individual’s hand abilities, such as coordination, sensation, motivation, and strength (McPhee, 1987). Consequently, matching hand function is specific to the person’s ability and the goals the client wishes to achieve. Data about an individual's grip strength do not provide enough information for the therapist to determine complete hand function. It is critical for an occupational therapist to see the hand in action (Conti, 1998). Developing efficient hand techniques may be a more important technique for hand function than improving strength itself (Rice, Leonard, & Carter, 1998). In addition, Conti (1998) explained that guided grasp techniques may be more effective than standard strengthening techniques because any Strength Determinates 5 given task may require different sequential muscle contractions by any of the 39 hand muscles that contribute to task completion. A task that requires hand function generally evokes people’s ability to use assorted types of grasping techniques. Napier (1956) studied gripping techniques including the power grip and precision grip, by examining people’s hands doing ordinary tasks, such as holding a ball and gripping a wooden cylinder. The power grip technique is when an object is held with partially flexed fingers, thumb, and the palm (e.g., holding a wooden rod), whereas the precision grip is when an object is pinched between the finger and thumb (e.g., holding a can of soda). He surmised that gripping consists of dynamic or static movements. Dynamic gripping is the action required while producing a grip, and static grip is the final state that indicates a grip. Landsmeer (1962) continued Napier’s study by examining hand mechanics and determined that precision handling is the dynamic phase of a gripping task. The author described that the dynamic phase is the act of opening the hand, aligning the fingers, approaching the fingers to the object, and static gripping of the object. This leads to the conclusion that after dynamic movements of the fingers and hand contact with a particular entity, object manipulation can occur. Occupational therapists test hand function in relation to typical gripping patterns more realistic to daily occupations. Skerik, Weiss, and Flatt (1971) examined traditional tests for hand function (i.e., range of motion, strength, etc.) performed by occupational therapists, and concluded they were dissimilar and too precise to represent everyday hand tasks. Therefore, Skerik et al. urged that testing should be relevant to hand functions in relation to the five prehension patterns, which include power grip, lateral pinch, hook grip, tip pinch, and palmer pinch (1971). These five terms describe dynamic and static Strength Determinates 6 hand manipulation techniques commonly used when the palm, fingers, and thumb are functioning jointly to perform an occupation. A lateral pinch is when an object, such as a key, is held by the palmar surface of the distal phalanx of the thumb against the lateral side intermediate and distal interphalangeal joint of the index finger (Skerik et al., 1971). Skerik et al. (1971) defined the palmer pinch as using the pads of index and thumb with the two digits forming a tapered oval from the radial view to hold and small object (e.g., needle). The tip pinch occurs when the tips of the index and thumb fingers are flexed in order to hold or pick up an object (e.g., a tack). A person holding a bag with handles with just the phalanges in a fixed flexed position is an example of a hook grip prehension pattern. Skerik et al. (1971) do not define power grip due to their contention that cylindrical and spherical grips patterns define the object being held rather than describing the grip being used. They propose that depending on the item being held, a tennis ball or a cup, power grip uses precision grip patterns already described. Holding a container requires hand strength and range of motion, as well as a combination of other factors, which include reliance upon sensation and motoric abilities. That is, they adapt to many facets of an occupation, utilizing prehension patterns may be a more effective way of improving a person’s ability to use his/her hand. The dynamic and static manipulations (prehension patterns) of an object are based on a person’s ability to perceive and comprehend the specific characteristics of the occupational form. This is followed by a “mapping” of these perceptions to the body’s specific potential movement strategies. Movement strategies are learned over time due to the gaining of knowledge for action that acquires specific movement patterns in relation to the task demands (Newell, 1991). The perceptual-motor workspace describes this Strength Determinates 7 process in relation to a person’s environmental, organisimc, and task constraints (Turvey and Kugler, 1984). This information is a method for which a person can locate taskrelevant solutions for the purpose of coordinating function (Newell, 1991). For example, a patient with arthritic hands may learn to grasp a phone differently because previous attempts caused a negative, painful reaction. Therefore, the patient may change the previous movement based on learned strategy through the perceptual-motor workspace constraints. Newell (1986) also indicated that the arrangement of a specific occupation is characterized by three types of constraints: environmental, task, and organisimc. These constraints provide information for an individual’s boundaries, options, and opportun