Background: Knee joint power is significantly impaired during the propulsive phase of jumping after anterior cruciate ligament reconstruction (ACLR); however, it is currently unknown how quadriceps strength influences knee joint power. Purpose: To (1) evaluate the relationship between quadriceps strength, joint power, and the percentage contribution of the hip, knee, and ankle joints to total limb power during the propulsive phase of jumping and (2) establish a quadriceps strength cutoff value for maximizing the likelihood of having knee joint power characteristics similar to healthy participants. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 75 participants were included in this study—40 patients who underwent ACLR 6 months before (18 females; mean age, 19.3 ± 5.7 years) and 35 healthy controls (HC) (20 females; mean age, 21.5 ± 4.5 years). Participants performed a drop vertical jump and underwent isometric quadriceps strength testing. The peak joint power was calculated as the product of the internal joint moment and joint angular velocity. Pearson product-moment correlations were used to assess the relationship between quadriceps strength and knee joint power. Paired samples t tests were used to quantify differences between limbs. Receiver operating characteristic (ROC) curve analysis was used to determine a quadriceps strength cutoff. Results: The involved limbs of the ACLR cohort (INV) had significantly lower peak knee joint power and percentage contribution from the knee joint during jumping compared with the uninvolved limbs (NON) and limbs of the controls (INV, 2.5 ± 1.2 W/kg; NON, 4.4 ± 1.5 W/kg; HC, 4.3 ± 1.7 W/kg [ P < .0001]). Quadriceps strength was associated with knee joint power in involved limbs and limbs of controls (INV, r = 0.50; HC, r = 0.60). A quadriceps strength cutoff value of 2.07 N·m/kg had an area under the ROC curve of 0.842, indicating good predictive accuracy. Conclusion: Athletes at 6 months after ACLR demonstrated knee-avoidant jumping mechanics and had significant reductions in knee joint power on the involved limb. A quadriceps strength cutoff value of 2.07 N·m/kg can help predict which athletes will display knee joint power characteristics similar to those of healthy controls.
Objective: We evaluated associations between vitamin D status and skeletal muscle, strength, and bone mineral density (BMD) outcomes after ACL reconstruction (ACLR) in an observational study. Methods: Serum measures included 25-hydroxyvitamin D (25(OH)D; free and total), vitamin D binding protein (DBP), and 1,25-dihydroxy vitamin D (1,25(OH)2D) at baseline, 1 week, 4 months, and 6 months post-ACLR. Vastus lateralis biopsies were collected from the healthy and ACL-injured limb of 21 young, healthy participants (62% female; 17.8 [3.2] yr, BMI: 26.0 [3.5] kg/m2) during ACLR and the injured limb only at 1 week and 4 month follow ups. RNA and protein were isolated from biopsies and assessed for vitamin D receptor [VDR], and vitamin D-activating enzymes. Quadriceps fiber cross-sectional area (CSA) was determined with immunohistochemistry. BMD of femur and tibia were determined with at baseline and 6 months post-ACLR; strength was assessed with an isokinetic dynamometer. Results: 1,25(OH)2D decreased from baseline to one week after ACLR (21.6 [7.9] vs. 13.8 [5.5] pg/mL; p<0.0001). VDR and 25-hydroxylase transcript abundance and VDR and DBP proteins were elevated one week after ACLR compared with baseline (FDR<0.05; p<0.05). Participants with an average total 25(OH)D <30 ng/mL showed significant decreases in CSA 1 week and 4 months after ACLR (p<0.01; p=0.041 for time x D status interaction), whereas those with total 25(OH)D ≥30ng/mL showed no significant differences (p>0.05 for all comparisons). BMD and strength measures were lower at follow up but did not associate with vitamin D status. Conclusion: ACLR promotes vitamin D pathways in the quadriceps and low status is associated with loss of skeletal muscle both 1 week and 4 months after ACLR.
baseline, there were no significant differences among groups for DI o [median values ranged from 1.97 (3.00) mM -1 for LM to 2.48 (3.14) mM -1 for HV]. After 6 months of exercise training, only the CL group significantly improved DI o [0.71 (0.28-1.15) mM -1 ;p=0.002]. Within-group changes for the exercise-only groups were 0.10 (-0.68-0.87) mM -1 for LM; -0.19 (-0.73-0.34) mM -1 for HM; and -0.41 (-0.83-0.02) mM -1 for HV. The Kruskal-Wallis test revealed changes in DI o were significantly better for the CL group compared to both high amount groups. CONCLUSIONS: For adults with prediabetes, combining a dietary intervention and weight loss with aerobic exercise improves DI o . Compared to findings from previous STRRIDE studies, improving β-cell function appears to be more challenging with aerobic exercise alone for those with a glycemic status closer to type 2 diabetes. Supported by NIH R01DK081559 828 Rate Of Torque Development Improvements Are Greatest Within First 2 Weeks Of Power-based Training
RESULTS:Average energy consumption decreased from pre-surgery to post-surgery (1797.3 ± 588.9 vs. 1587.8 ± 604.9, respectively; p=0.029). Comparisons pre-and post-surgery for weight (74.9 kg ±18.0 vs. 74.5 ± 18.5), kcal/kg (24.8 ± 7.5 vs 22.3 ± 8.8), and protein g/kg (0.99 ± 0.35 vs. 0.97 ± 0.44) did not show differences. HEI-2015 was significantly lower in teenagers pre-and post-surgery compared to the US average of 53 for Americans age 2-19 (42.4 ± 8.5; p <.001; 42.7 ± 9.8; p <.001). Adult participants' HEI was significantly lower than the US average of 59 only after ACL reconstruction (53.2 ± 13.3; p= 0.073; 50.5 ± 13.2; p= 0.011). Children had significantly lower HEI-2015 than adults before reconstruction (42.4 ± 8.5 vs 53.2 ± 13.3; p=0.007) but not after (42.7 ± 9.8 vs 50.5 ± 13.2; p=0.057). CONCLUSION: On average, energy intake decreases following ACL surgery in young participants. Future research should address links between diet quality, reduced energy intake and recovery following ACL surgery.
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