Hm. Holder-powell et al., Do knee injuries have long-term consequences for isometric and dynamic muscle strength?, EUR J A PHY, 85(3-4), 2001, pp. 310-316
To ascertain whether decrements in knee extensor muscle strength persist ye
ars after a traumatic ligamentous or meniscal knee injury, with reference t
o (1) the type of muscle activity, (2) the dominance of injury, and (3) the
time since injury, 36 subjects with previous unilateral knee injuries were
assessed. Peak voluntary quadriceps muscle strength was measured using the
KinCom 500H dynamometer during isometric, concentric (30 degrees .s(-1) an
d 120 degrees .s(-1)) and eccentric contractions (30.s(-1)), and the findin
gs for each type of contraction were compared. Significant differences in q
uadriceps muscle strength were seen between (1) the injured and uninjured l
imbs during maximal voluntary isometric (P=0.0003), concentric (P<0.0001) a
nd eccentric (P<0.0001) contractions, and (2) the isometric and concentric
decrements (P = 0.004), and the isometric and eccentric decrements (P=0.012
) within the same injured limb. The decrements in eccentric strength were s
ignificantly greater if they affected the dominant rather than the non-domi
nant limb (P=0.0186). No relationship was seen between the time since injur
y and the degree of isometric or dynamic decrement. Deficits in quadriceps
muscle strength remained for a long time after traumatic knee injury, with
exercise levels rarely returning to the previously uninjured state. The deg
ree of decrement in muscle strength was dependent upon the type of muscle a
ctivity, with concentric and eccentric activity showing greater decrements
than those seen with isometric activity. Deficits in the type of activity v
aried widely in the same individual, and eccentric decrements were signific
antly worse following dominant knee injuries. Possible explanations for the
se findings and the implications for rehabilitation following knee injury a
re discussed.