Scientific/Clinical ArticleUsing the Force–Time Curve to Determine Sincerity of Effort in People with Upper Extremity Injuries
Section snippets
Participants
Forty participants with current upper extremity injuries (20 men and 20 women) were recruited from various hand therapy and rehabilitation clinics in North-Central Florida. The sample size was estimated based on a power analysis of data from a previous study using healthy participants.1 Physical and occupational therapists identified and recruited patients who met the study criteria. Inclusion criteria were 1) age between 18 and 65 years and 2) treated for unilateral upper extremity injuries
Results
Demographic and injury-related data are summarized in Table 1. The average values of the F–T curve slopes are found in Table 2. The slopes of force-generation phase were significantly steeper for maximal effort when compared with submaximal effort [F (1, 38) = 55.77, p ≤ 0.0001], uninjured hand when compared with injured hand [F (1, 38) = 9.44, p ≤ 0.004], and men compared with women [F (1, 38) = 7.61, p ≤ 0.009] (Table 3, Figure 2). Similarly, the slopes of force-decay phase were significantly steeper for
Discussion
The slopes of the force-generation and force-decay phases of the F–T curve were found to be valid in determining the sincerity of effort in healthy people.1 The purpose of this study was to examine if these slopes can validly distinguish between maximal and submaximal grip efforts among people with upper extremity injuries. A valid sincerity-of-effort test should reveal significant differences between maximal and submaximal efforts, and indeed, we found significant differences for the slopes of
Conclusions
The significantly steeper slopes for maximal efforts when compared with submaximal efforts indicated that the slopes of the force-generation and force-decay phases of the F–T curve can differentiate between maximal and submaximal efforts in people with upper extremity injury. However, sensitivity and specificity values were insufficient to effectively differentiate maximal from submaximal efforts, perhaps, because participants were protective of their injured hand and, thus, exerted only
Acknowledgment
This work was supported in part by the Evelyn Mackin Research Grant of the American Society of Hand Therapists. Partial equipment support was provided by Thought Technology Ltd., Montreal, Quebec, Canada.
Quiz: Article #174
Record your answers on the Return Answer Form found on the tear-out coupon at the back of this issue or to complete online and use a credit card, go to JHTReadforCredit.com. There is only one best answer for each question.
- #1.
According to the motor unit recruitment model, maximal effort
- a.
cannot be approximated
- b.
requires synchronous firing of all motor units
- c.
requires simultaneous and maximal activation of all motor units
- d.
does not result in fatigue of motor units
- a.
- #2.
The slope of the force-decay phase of a
References (40)
- et al.
Using the force-time curve to detect maximal grip strength effort
J Hand Ther
(2007) - et al.
Reliability and validity of grip and pinch strength evaluations
J Hand Surg [Am]
(1984) - et al.
Rapid repeat testing of grip strength for detection of faked hand weakness
J Hand Surg [Br]
(2000) - et al.
The use of the rapid exchange grip test in detecting sincerity of effort, part I: administration of the test
J Hand Ther
(2000) - et al.
The use of the rapid exchange grip test in detecting sincerity of effort, part II: validity of the test
J Hand Ther
(2000) Using the coefficient of variation to detect sincerity of effort of grip strength: a literature review
J Hand Ther
(2000)The coefficient of variation as a measure of sincerity of effort of grip strength, part II: sensitivity and specificity
J Hand Ther
(2001)The coefficient of variation as a measure of sincerity of effort of grip strength, part I: the statistical principle
J Hand Ther
(2001)- et al.
How do therapists administer the rapid exchange grip test? A survey
J Hand Ther
(2002) - et al.
Reliability and validity of the BTE-Primus grip tool
J Hand Ther
(2003)