The effect of short-duration sub-maximal cycling on balance in single-limb stance in patients with anterior cruciate ligament injury: a cross-sectional study

Abstract

Background: It has previously been shown that an anterior cruciate ligament (ACL) injury may lead to impaired postural control, and that the ability to maintain postural control is decreased by fatigue in healthy subjects. To our knowledge, no studies have reported the effect of fatigue on postural control in subjects with ACL injury. This study was aimed at examining the effect of fatigue on balance in single-limb stance in subjects with ACL injury, and to compare the effects, and the ability to maintain balance, with that of a control group of uninjured subjects.

Methods: Thirty-six patients with unilateral, non-operated, non-acute ACL injury, and 24 uninjured subjects were examined with stabilometry before (pre-exercise) and immediately after (post-exercise) short-duration, sub-maximal cycling. In addition, the post-exercise measurements were compared, to evaluate the instantaneous ability to maintain balance and any possible recovery. The amplitude and average speed of center of pressure movements were registered in the frontal and sagittal planes. The paired t-test was used for the intra-group comparisons, and the independent t-test for the inter-group comparisons, with Bonferroni correction for multiple comparisons.

Results: No differences were found in the effects of exercise between the patients and the controls. Analysis of the post-exercise measurements revealed greater effects or a tendency towards greater effects on the injured leg than in the control group. The average speed was lower among the patients than in the control group.

Conclusions: The results of the present study showed no differences in the effects of exercise between the patients and the controls. However, the patients seemed to react differently regarding ability to maintain balance in single-limb stance directly after exercise than the control group. The lower average speed among the patients may be an expression of different neuromuscular adaptive strategies than in uninjured subjects.

Figure 1

Stabilometry in single-limb stance, tested by means of a strain gauge force plate. A standardized position was used. The subject is a model who did not participate in the study. Reprinted from Ageberg E, Zätterström R, Moritz U, Fridén T. Influence of supervised and nonsupervised training on postural control after an acute anterior cruciate ligament rupture: A 3-year longitudinal prospective study. Journal of Orthopaedic & Sports Physical Therapy. 2001:31: 632–644, with permission of the Orthopaedic and Sports Sections of the American Physical Therapy Association.

Figure 2

Raw data from a stabilometry trial. A measurement in the frontal plane for the right leg in a subject who did not participate in the study. The reference line, the mean value of center of pressure (CP), and movements of the CP are shown in the Figure. In this trial, the average speed was 20 mm·s^-1 and the number of DEV 10 was 5.

Figure 3

Pre- and post-exercise values. Average speed (mm·s^-1) in the frontal plane (FP) pre- and post-exercise, for the injured leg of the patients and the uninjured legs of the control group. The circles denote outliers (i.e., cases with values between 1.5 and 3 box lengths from the upper or lower edge of the box).

Figure 4

Pre- and post-exercise values. Average speed (mm·s^-1) in the sagittal plane (SP) pre- and post-exercise, for the injured leg of the patients and the uninjured legs of the control group. The asterisks denote extreme values (i.e., cases with values more than 3 box lengths from the upper or lower edge of the box).

Figure 5

Pre- and post-exercise values. DEV 10 (n) in the frontal plane (FP) pre- and post-exercise, for the injured leg of the patients and the uninjured legs of the control group. The circles denote outliers (i.e., cases with values between 1.5 and 3 box lengths from the upper or lower edge of the box), and the asterisks denote extreme values (i.e., cases with values more than 3 box lengths from the upper or lower edge of the box).

Figure 6

Pre- and post-exercise values. DEV 10 (n) in the sagittal plane (SP) pre- and post-exercise, for the injured leg of the patients and the uninjured legs of the control group. The circles denote outliers (i.e., cases with values between 1.5 and 3 box lengths from the upper or lower edge of the box), and the asterisks denote extreme values (i.e., cases with values more than 3 box lengths from the upper or lower edge of the box).

Figure 7

Post-exercise measurements 1 and 3. Average speed (mm·s^-1) in the frontal plane (FP) post-exercise measurements 1 and 3, for the injured leg of the patients and the uninjured legs of the control group. The circles denote outliers (i.e., cases with values between 1.5 and 3 box lengths from the upper or lower edge of the box).

Figure 8

Post-exercise measurements 1 and 3. Average speed (mm·s^-1) in the sagittal plane (SP) post-exercise measurements 1 and 3, for the injured leg of the patients and the uninjured legs of the control group. The asterisks denote extreme values (i.e., cases with values more than 3 box lengths from the upper or lower edge of the box).

Figure 9

Post-exercise measurements 1 and 3. DEV 10 (n) in the frontal plane (FP) post-exercise measurements 1 and 3, for the injured leg of the patients and the uninjured legs of the control group. The circles denote outliers (i.e., cases with values between 1.5 and 3 box lengths from the upper or lower edge of the box), and the asterisks denote extreme values (i.e., cases with values more than 3 box lengths from the upper or lower edge of the box).

Figure 10

Post-exercise measurements 1 and 3. DEV 10 (n) in the sagittal plane (SP) post-exercise measurements 1 and 3, for the injured leg of the patients and the uninjured legs of the control group. The circles denote outliers (i.e., cases with values between 1.5 and 3 box lengths from the upper or lower edge of the box), and the asterisks denote extreme values (i.e., cases with values more than 3 box lengths from the upper or lower edge of the box).