| Summary: | Purpose
The main purpose of this study was to determine the effectiveness of
proprioceptive training in the ACL reconstructed limb. The second purpose of this study
was to determine the relative contribution of isokinetic strength and peak hamstring
torque time to functional ability.
Methods
Ten subjects with unilateral ACL reconstructed limbs were randomly assigned to
two experimental groups. Group One (Strength Training Group) consisted of five
subjects who were placed on a 12 week general lower body strength training program.
Group Two (Proprioceptive Group) consisted of five subjects who were placed on a 12
week proprioceptive training program for the lower extremities. Peak hamstring torque
time (PTT) was measured using the protocol described by Small et al.¹. Average
concentric and eccentric torques of the quadriceps and hamstring muscles were measured
using the KIN-COM isokinetic dynamometer. Functional ability was determined by the
one-legged single hop for distance (SLHD) and the one-legged timed hop. Subjective
scores were obtained from the Lysholm and Gillquist Knee Scoring Scale and the Tegner
and Lysholm Activity Scale.
Results
Both training protocols were found to influence peak hamstring torque time of the
ACL reconstructed limb. No significant differences were found between or within the
two experimental groups. However, a group by test occasion interaction effect on peak
hamstring torque time was found. A curvilinear relationship between PTT and test
occasion was evident for both experimental groups. The strength training group
demonstrated a slowing of PTT at 6 weeks, while the proprioceptive training group
demonstrated an improvement in PTT at 6 weeks. At the end of the 12 weeks, both
experimental groups regressed toward their baseline PTT values, such as the strength
training group demonstrated an improvement in PTT while the proprioceptive training
group demonstrated a slowing of PTT in the latter six weeks.
There was a significant group by test occasion interaction effect on isokinetic
strength measures. The proprioceptive group demonstrated greater isokinetic strength
gains than the strength training group after 12 weeks of training. Both experimental
groups demonstrated similar significant gains in functional ability. Both groups also
demonstrated similar significant gains in the subjective assessment (Lysholm and
Gillquist Knee Scoring Scale) and the subjective analysis of physical function (Tegner
and Lysholm Activity Scale) after 12 weeks of training.
Regressional analyses indicated isokinetic strength of the quadriceps and the
hamstring muscles to have significant effects on functional ability (SLHD). Average
concentric hamstring torque was found to have the most significant effect on functional
ability.
Conclusion
Both strength training and proprioceptive training have an influence on peak
torque time. It is proposed that the two types of training influence PTT through different
neuromuscular mechanisms. Strength training is proposed to positively influence PTT by
increasing fast twitch/slow twitch (FT/ST) muscle area ratio and to negatively influence
PTT by decreasing muscle spindle sensitivity. Proprioceptive training is proposed to
positively influence PTT by improving coordination and neural activation of the
appropriate muscles. Coordination relies on proprioception and kinesthesia. However,
the effectiveness of proprioceptive training is dependent on appropriate progression and
repetition. Early integration of speed, force, and complexity of movement into
proprioceptive training may decrease the effectiveness of training. Thus, the integration
of these components should only occur if precision of performing motor tasks is not
compromised.
Both strength training and proprioceptive training may have beneficial effects on
subjective scores and functional ability. Greater isokinetic strength gains can be observed
with proprioceptive training than with strength training as training occurs over time.
These greater isokinetic strength gains are proposed to be secondary to improved muscle
coordination and neural activation rather than actual muscular hypertrophy.
The strength of the lower extremities contribute significantly to functional ability.
The strength of the hamstring muscle appear to play a greater role in functional ability
than the quadriceps.
However, due to the small sample size used in this study, the ability to generalize
these results may be limited.
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