Effects of isometric contraction of the quadriceps on the hardness and blood flow in the infrapatellar fat pad

Effect of isometric quadriceps exercise on local microcirculation of the infrapatellar fat pad in female patients with knee osteoarthritis

OBJECTIVE

To elucidate the local microcirculation of the infrapatellar fat pad (IFP) in patients with knee osteoarthritis (KOA) by determining the changes in IFP hardness and hemoglobin concentration during isometric quadriceps exercise (IQE).

DESIGN

In this observational cross-sectional study, patients diagnosed with bilateral KOA were included in the KOA group (30 knees), healthy older adults in the control group (20 knees), and younger adults in the young group (20 knees). Ultrasonography was performed at rest and during IQE to measure IFP hardness based on shear wave velocity. Near-infrared spectroscopy was performed to measure oxygenated hemoglobin (O2Hb), deoxygenated hemoglobin (HHb), and total hemoglobin (cHb) in the IFP before (Baseline), during (IQE task), and after IQE (Post). IFP hardness and O2Hb, HHb, and cHb concentration were analyzed using a linear mixed model for the groups and measurement points.

RESULTS

During IQE, IFP hardness changes were significantly less in the KOA group than in the other groups (KOA: 95 % confidence intervals (CIs) [-0.854, 0.028]; control: 95 % CI [-0.941, -0.341]; and young: 95 % CI [-2.305, -1.706]). In the KOA group, O2Hb concentration exhibited no significant changes at Post compared with Baseline; however, significant changes were observed in the other groups (KOA: 95 % CI [-1.176, 0.423]; control: 95 % CI [-1.452, -0.276]; and young: 95 % CI [-4.062, -2.102]).

CONCLUSIONS

During IQE, changes in hardness and hemoglobin concentration in the IFP were not significant in the KOA group, suggesting impaired local microcirculation of the IFP.

Validation of anterior ankle soft tissue dynamics and shear modulus for anterior ankle impingement syndrome after ankle fracture surgery

Anterior ankle impingement syndrome (AAIS) has been reported to account for a high percentage of complications following ankle fracture surgery. The soft tissue etiology of AAIS is thought to be thickening and inflammation of the anterior ankle soft tissues intervening anteriorly at the tibiotalar joint, causing pain and functional limitation during dorsiflexion. However, the effects of anterior ankle soft tissue dynamics and stiffness on AAIS have yet to be clarified. This study aimed to determine the relationship between AAIS and the anterior ankle soft tissue thickness change ratio and shear modulus using ultrasonography (US). The participants were 20 patients with ankle joint fractures (AO classification A, B) who had undergone open reduction and internal fixation and 20 healthy adults. The evaluation periods were 3 months and 6 months postoperatively. US was used to delineate the tibialis anterior tendon, extensor hallucis longus tendon, and the extensor digitorum longus tendon over the talus and tibia on a long-axis image. Anterior ankle soft tissue thickness was measured as the shortest distance from the most convex part of the talus to the tendon directly above it. The Anterior ankle soft tissue thickness change ratio was determined by dividing the value at 0° dorsiflexion by the value at 10° plantarflexion. The same images as for the anterior soft tissue thickness measurement were drawn for the shear modulus measurement, and the average shear modulus (kPa) was calculated using shear-wave elastography. There was no significant difference in the thickness change ratio between the postoperative and healthy groups. Compared with the healthy group, the shear modulus was significantly higher at 3 and 6 months in the postoperative group (p < 0.01). The shear elastic modulus at 6-month postoperative group was significantly lower than at 3-month postoperative group (p < 0.01). Anterior ankle joint soft tissue stiffness may increase after surgery for an ankle fracture.

Effects of isometric loading intensity on patellar tendon microvascular response

Acute increases in tendon blood flow and oxygenation after stress (i.e., hyperemic response) can enhance tendon recovery. While loading intensity is a fundamental part of resistance training programs, its effects on tendon's hyperemic response are unknown. This study aimed to compare acute changes in total (total hemoglobin [THb]) and oxygenated hemoglobin (HbO₂ ) concentrations in the patellar tendon after isometric exercise at different intensities. Thirteen participants performed 8 (5 s) isometric knee extensions at 25%, 50%, and 75% maximal load (maximal voluntarily isometric contraction [MVIC]), separated by 20 min recovery, prescribed in randomized and counterbalanced order. Changes in patellar tendon THb, HbO₂ and deoxygenated hemoglobin (HHb) in response to exercise at each intensity were measured using near-infrared spectroscopy. Post-exercise, HbO₂ increased with 50% ( η p 2 $$ {\eta}_p^2 $$  = 0.305, f = 5.26, p < 0.01) and 75% ( η p 2 $$ {\eta}_p^2 $$  = 0.245, f = 4.56, p < 0.01) but not 25% ( η p 2 $$ {\eta}_p^2 $$  = 0.088, f = 1.16, p = 0.339) MVIC, while THb increased in 50% ( η p 2 $$ {\eta}_p^2 $$  = 0.305, f = 5.26, p = 0.01) but not 25% ( η p 2 $$ {\eta}_p^2 $$  = 0.067, f = 0.865, p = 0.51) or 75% ( η p 2 $$ {\eta}_p^2 $$  = 0.126, f = 1.729, p = 0.14) MVIC. Additionally, increasing load from 25% to 50% MVIC resulted in greater THb (f = 2.459, p = 0.43), HbO₂ (f = 3.389, p = 0.13) and HHb (f = 0.320, p = 0.01) post-exercise responses, but no differences were observed between 50% and 75% MVIC (THb: f = 0.748, p = 0.59; HbO₂ : f = 0.825, p = 0.54; HHb: f = 0.713, p = 0.62). Our results suggest there is a loading threshold at ~50% MVIC at which the tendon hyperemic response is fully achieved. Training above this intensity is not expected to provide any additional change to the tendon microvascular response. Therefore, moderate loading seems to be sufficient to fully elicit the patellar tendon hyperemic response that's believed to stimulate tendon healing.