Journal of Rehabilitation Medicine 51-4inkOmslag | Page 20

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R. Stock et al.
Table II. Mean (SD) grip strength of the non–affected and affected sides and mean (95% CI) difference between sides (n  = 11 if not
otherwise indicated)
Sides
Grip strength
Difference between sides
Week 2
Week 28
Non-aff Aff Non-aff Aff Non-aff Aff
276 (109)
362 (99)
337 (89)
289 (71)
235 (57)
83 (21)
85 (18)
57 (10) 116 (72)
165 (109)
149 (90)
136 (78)
115 (61)
46 (19)
38 (15)
25 (12) 271 (104)
370 (103)
334 (90)
288 (75)
237 (59)
83 (20)
86 (16)
55 (10) 176 (85)
258 (118)
235 (116)
200 (90)
165 (71)
66 (26)
61 (20)
41 (14) 282 (108)
371 (107)
342 (93)
295 (85)
247 (71)
82 (20)
85 (17)
57 (9) 227 (112)
299 (126)
266 (107)
231 (95)
193 (82)
70 (27)
65 (19)
43 (15)
530 (196)
138 (35) 204 (203)
63 (39) 501 (206)
136 (49) 370 (251)
111 (54) 507 (215)
138 (47) 403 (242)
121 (52)
27 (10) 35 a (11) 32 (9) 36 a (8)
28 (5) 44 (13) 32 (8)
Mean (SD) Mean (SD)
Maximum force (N)
Power (Position 1)
Power (Position 2)
Power (Position 3)
Power (Position 4)
Power (Position 5)
Pinch (Key)
Pinch (3-finger)
Pinch (2-finger)
Rate of force development (N/s)
Power (Position 2)
Pinch (Key)
Sustainability of force (% of initial force at 12 s)
Power (Position 2)
26 (10)
33 a (7)
Pinch (Key)
Week 54
56 a (14)
53 b (20)
Mean (SD)
Mean (SD)
Mean (SD)
Mean (SD)
37 a (12)
Week 28–Week 2 Week 54– Week 2
Non-aff – Aff Non-aff – Aff
Mean (95% CI)
–65
–85
–89
–66
–48
–20
–22
–18
(–12 to –119)
(–34 to –136)
(–40 to –138)
(–33 to –99)
(–23 to –73)
(–9 to –30)
(–11 to –32)
(–10 to –26)
–194 (–93 to –295)
–49 (–29 to –70)
23 (7 to 39)
8 (–6 to 22)
Mean (95% CI)
–105 (–50 to –160)
–124 (–72 to –176)
–112 (–67 to –157)
–89 (–51 to –126)
–66 (–37 to –96)
–25 (–14 to –37)
–26 (–15 to –38)
–18 (–10 to –27)
–222 (–148 to –295)
–58 (–32 to –83)
26 (12 to 41)
12 (–3 to 28)
a
n  = 10, b n  = 9.
Non-aff: non-affected hand; Aff: affected hand; CI: confidence interval.
DISCUSSION
This study examined the recovery of hand grip and
pinch strength during the first year after stroke in pa-
tients with mild to moderate stroke. Maximum force
in the affected hand increased most during the first 2
weeks, followed by quite stable improvement up to 1
year after stroke. Grip force was highest in position 2
(second most narrow grip) on the hand dynamometer
for both the affected and non-affected hand. No signi-
ficant differences between the hands were found with
respect to position-dependent weakness. The ability to
generate grip force rapidly was lower on the affected
side at W2; however, this difference was no longer
present at 6 months. At W2, the ability to sustain maxi-
mum grip force declined more rapidly on the affected
side compared with the non-affected side (to 45% vs
75% of maximum force, respectively) during the 12-s
sustained grip test. Notably, relative grip force on the
affected side decreased markedly during the first 2–3
s of the sustained grip test, especially at W2 and at the
4-week follow-up measurement, indicating increased
fatigability. However, the relative capacity to sustain
maximum grip force approached the values of the non-
affected side at 6 months post-stroke.
Grip strength
The recovery of grip strength in this study is gene-
rally comparable to the recovery curve described by
Langhorne et al. (2), with most improvement in mo-
tor function occurring during the first 6 months after
stroke. However, our study shows that hand grip force
continued to improve between 6 and 12 months, while
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we observed less improvement for the 3 types of pinch
grip force during this period. Maximum force and grip
force ratios (maximum force affected/maximum force
non-affected hand) were similar to other studies with
stroke patients with mild to moderate impairment (6).
Key grip force at W2 showed a higher force ratio, i.e.
force on the affected side was relatively higher, com-
pared with 3-finger grip and 2-finger grip. In addition,
the difference in key grip force between the affected
and non-affected hand at 1-year follow-up was less
pronounced than for the 3-finger and 2-finger grip. A
possible explanation for the better preserved key grip
force might be that the key grip demands less dexterity
and coordination between the fingers.
There are no comparable longitudinal studies on
the recovery of hand grip force in different positions.
In contrast to Ada et al. (8), we found no evidence of
selective weakness in the affected compared with the
non-affected side. It is possible that selective weakness
may apply to patients with more severe impairment.
Rate of force development
In general, measurements of rate of force development
have lower reliability than measurements of MVC
(26), and the highest variation in muscle force usually
occurs during the initial 0.2–0.3 s period. Demura et
al. (22) reported higher reliability for rate of force
development, with time intervals from 500 ms up to
2,000 ms (ICC 0.77 and 0.93 respectively) compared
with shorter intervals, as well as for peak rate of force
development (ICC 0.67). Due to the high variation
during shorter intervals and because longer intervals
do not measure the ability to generate force quickly,