Mechanics of the Patellar Tendon in Elite Volleyball Players
Mechanics of the Patellar Tendon in Elite Volleyball Players
Absolute and relative patellar tendon stiffness and Young's modulus were significantly lower in the patellar tendinopathy group compared to controls (32%, 20%, 29% and 15%, respectively; figure 3). Stiffness and Young's modulus for formerly healthy participants with current patellar tendinopathy were similar to that for symptomatic participants for both relative and absolute values. Participants with quadriceps tendinopathy had similar values compared to participants in the control group for both relative and absolute stiffness and Young's modulus. Force, stiffness, stress, strain, elongation and Young's modulus values for the patellar tendon for the patellar tendinopathy and control groups are shown in Table 3.
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Figure 3.
Image showing stiffness (A and B) and Young's modulus (C and D) for the patellar tendinopathy group (n=12 and 13 for the relative and absolute values, respectively), control group (n=15), formerly healthy participants with current patellar tendinopathy (n=3) and the quadriceps tendinopathy group (n=3). Values are presented in both relative (A and C) and absolute (B and D) values. The horizontal lines represent the group means.
Tendon proximal CSA was 19% larger in the patellar tendinopathy group than in the control group (figure 4).
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Figure 4.
Image showing the tendon cross-sectional area (CSA) for the patellar tendinopathy group (open figures; n=13) and control group (closed figures; n=15 (distal CSA, n=13)) at the proximal, middle and distal parts of the tendon; mean±SD. *Significantly different from control, p<0.001. When comparing middle CSA with the same controls used for distal CSA (n=13) to the patellar tendinopathy group (n=13), no significant difference was found (p=0.92).
The patellar tendinopathy group had a significantly greater (183%) CMJ–SJ difference compared to the controls (figure 5). There were no differences in spike jump, SJ and CMJ performance between the two groups (Table 4); however, when data from the quadriceps tendinopathy group (n=3) were combined with those of the patellar tendinopathy group (n=16), there was a significant difference in the spike jump height (7 cm, 0.07–14) and spike jump reach (6 cm, 0.5–11) compared to controls.
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Figure 5.
Image showing the SJ (squat jump) height (A), CMJ (countermovement jump) height (B), CMJ–SJ difference (C) and spike jump height (D) for the patellar tendinopathy group (n=13), control group (n=15), formerly healthy participants with current patellar tendinopathy (n=3) and quadriceps tendinopathy groups (n=3). Horizontal lines represent the group means.
There were no significant differences in the peak rate of force development between the patellar tendinopathy and control groups (figure 6).
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Figure 6.
Image showing the isometric knee extension peak rate of force development (RFDpeak) for the patellar tendinopathy (n=13) and control (n=15) groups, formerly healthy participants with current patellar tendinopathy (n=3) and quadriceps tendinopathy groups (n=3). Horizontal lines represent group means.
Results
Mechanical and Material Properties
Absolute and relative patellar tendon stiffness and Young's modulus were significantly lower in the patellar tendinopathy group compared to controls (32%, 20%, 29% and 15%, respectively; figure 3). Stiffness and Young's modulus for formerly healthy participants with current patellar tendinopathy were similar to that for symptomatic participants for both relative and absolute values. Participants with quadriceps tendinopathy had similar values compared to participants in the control group for both relative and absolute stiffness and Young's modulus. Force, stiffness, stress, strain, elongation and Young's modulus values for the patellar tendon for the patellar tendinopathy and control groups are shown in Table 3.
(Enlarge Image)
Figure 3.
Image showing stiffness (A and B) and Young's modulus (C and D) for the patellar tendinopathy group (n=12 and 13 for the relative and absolute values, respectively), control group (n=15), formerly healthy participants with current patellar tendinopathy (n=3) and the quadriceps tendinopathy group (n=3). Values are presented in both relative (A and C) and absolute (B and D) values. The horizontal lines represent the group means.
Tendon proximal CSA was 19% larger in the patellar tendinopathy group than in the control group (figure 4).
(Enlarge Image)
Figure 4.
Image showing the tendon cross-sectional area (CSA) for the patellar tendinopathy group (open figures; n=13) and control group (closed figures; n=15 (distal CSA, n=13)) at the proximal, middle and distal parts of the tendon; mean±SD. *Significantly different from control, p<0.001. When comparing middle CSA with the same controls used for distal CSA (n=13) to the patellar tendinopathy group (n=13), no significant difference was found (p=0.92).
Jump Performance
The patellar tendinopathy group had a significantly greater (183%) CMJ–SJ difference compared to the controls (figure 5). There were no differences in spike jump, SJ and CMJ performance between the two groups (Table 4); however, when data from the quadriceps tendinopathy group (n=3) were combined with those of the patellar tendinopathy group (n=16), there was a significant difference in the spike jump height (7 cm, 0.07–14) and spike jump reach (6 cm, 0.5–11) compared to controls.
(Enlarge Image)
Figure 5.
Image showing the SJ (squat jump) height (A), CMJ (countermovement jump) height (B), CMJ–SJ difference (C) and spike jump height (D) for the patellar tendinopathy group (n=13), control group (n=15), formerly healthy participants with current patellar tendinopathy (n=3) and quadriceps tendinopathy groups (n=3). Horizontal lines represent the group means.
Isometric Rate of Force Development
There were no significant differences in the peak rate of force development between the patellar tendinopathy and control groups (figure 6).
(Enlarge Image)
Figure 6.
Image showing the isometric knee extension peak rate of force development (RFDpeak) for the patellar tendinopathy (n=13) and control (n=15) groups, formerly healthy participants with current patellar tendinopathy (n=3) and quadriceps tendinopathy groups (n=3). Horizontal lines represent group means.
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