Ryan Madden

Chondrocyte deformation under extreme tissue strain in two regions of the rabbit knee joint

Articular cartilage and its native cells-chondrocytes-are exposed to a wide range of mechanical loading. Chondrocytes are responsible for maintaining the cartilage matrix, yet relatively little is known regarding their behavior under a complete range of mechanical loads or how cell mechanics are affected by region within the joint. The purpose of this study was to investigate chondrocyte deformations in situ under tissue loads ranging from physiological to extreme (0-80% nominal strain) in two regions of the rabbit knee joint (femoral condyles and patellae). Local matrix strains and cell compressive strains increased with increasing loads. At low loads the extracellular matrix (ECM) strains in the superficial zone were greater than the applied tissue strains, while at extreme loads, the local ECM strains were smaller than the applied strains. Cell compressive strains were always smaller than the applied tissue strains and, in our intact, in situ preparation, were substantially smaller than those previously found in hemi-cylindrical explants. This resulted in markedly different steady-state cell volume changes in the current study compared to those working with cartilage explants. Additionally, cells from different regions in the knee exhibited striking differences in deformation behavior under load. The current results suggest: (i) that the local extracellular and pericellular matrix environment is intimately linked to chondrocyte mechanobiology, protecting chondrocytes from potentially damaging strains at high tissue loads; and (ii) that cell mechanics are a function of applied load and local cartilage tissue structure.

In situ chondrocyte viscoelasticity

It has been proposed, based on theoretical considerations, that the strain rate-dependent viscoelastic response of cartilage reduces local tissue and cell deformations during cyclic compressions. However, experimental studies have not addressed the in situ viscoelastic response of chondrocytes under static and dynamic loading conditions. In particular, results obtained from experimental studies using isolated chondrocytes embedded in gel constructs cannot be used to predict the intrinsic viscoelastic responses of chondrocytes in situ or in vivo. Therefore, the purpose of this study was to investigate the viscoelastic response of chondrocytes in their native environment under static and cyclic mechanical compression using a novel in situ experimental approach. Cartilage matrix and chondrocyte recovery in situ following mechanical compressions was highly viscoelastic. The observed in situ behavior was consistent with a previous study on in vivo chondrocyte mechanics which showed that it took 5-7 min for chondrocytes to recover shape and volume following virtually instantaneous cell deformations during muscular loading of the knee in live mice. We conclude from these results that the viscoelastic properties of cartilage minimize chondrocyte deformations during cyclic dynamic loading as occurs, for example, in the lower limb joints during locomotion, thereby allowing the cells to reach mechanical and metabolic homeostasis even under highly dynamic loading conditions.

Influence of Compression and Stiffness Apparel on Vertical Jump Performance.

Abstract Wannop, JW, Worobets, JT, Madden, R, and Stefanyshyn, DJ. Influence of compression and stiffness apparel on vertical jump performance. J Strength Cond Res 30(4): 1093–1101, 2016—Compression apparel alters both compression of the soft tissues and the hip joint stiffness of athletes. It is not known whether it is the compression elements, the stiffness elements, or some combination that increases performance. Therefore, the purpose of this study was to determine how systematically increasing upper leg compression and hip joint stiffness independently from one another affects vertical jumping performance. Ten male athletes performed countermovement vertical jumps in 8 concept apparel conditions and 1 control condition (loose fitting shorts). The 8 apparel conditions, 4 that specifically altered the amount of compression exerted on the thigh and 4 that altered the hip joint stiffness by means of elastic thermoplastic polyurethane bands, were tested on 2 separate testing sessions (one testing the compression apparel and the other testing the stiffness apparel). Maximum jump height was measured, while kinematic data of the hip, knee, and ankle joint were recorded with a high-speed camera (480 Hz). Both compression and stiffness apparel can have a positive influence on vertical jumping performance. The increase in jump height for the optimal compression was due to increased hip joint range of motion and a trend of increasing the jump time. Optimal stiffness also increased jump height and had the trend of decreasing the hip joint range of motion and hip joint angular velocity. The exact mechanisms by which apparel interventions alter performance is not clear, but it may be due to alterations to the force-length and force-velocity relationships of muscle.

Effects of shoe bending stiffness and surface stiffness on lower extremity biomechanics during running

where all experts score the foot as flexible or rigid, respectively. The root-mean-square error is 0.164 which means that the model can give a good prediction of the experts’ scores. Of the 21 foot characteristics we took into account, 15 of them scored a RMS lower than 0.2 with the lowest being 0.124, and 6 were higher than 0.2, with a maximum of 0.449. As expected, the prediction of the midfoot pressure was best using the pressure plate and was slightly improved when combining the pressure plate with a 3D scanner or 3D motion analysis. RCSP was best predicted using the 3D measurement system, or the 3D measurement system combined with the pressure data. Finally, the forefoot/heel ratio showed the best results combining 3D scanner data and pressure data.

Early in situ changes in chondrocyte biomechanical responses due to a partial meniscectomy in the lateral compartment of the mature rabbit knee joint

We determined the biomechanical responses of chondrocytes to indentation at specific locations within the superficial zone of cartilage (i.e. patellar, femoral groove, femoral condylar and tibial plateau sites) taken from female New Zealand white rabbits three days after a partial meniscectomy in the lateral compartment of a knee joint. Confocal laser scanning microscopy combined with a custom indentation system was utilized to image chondrocyte responses at sites taken from ten contralateral and experimental knee joints. Cell volume, height, width and depth changes, global, local axial and transverse strains and Young׳s moduli were determined. Histological assessment was performed and proteoglycan content from the superficial zone of each site was determined. Relative to contralateral group cells, patellar, femoral groove and lateral femoral condyle cells in the experimental group underwent greater volume decreases (p < 0.05), due to smaller lateral expansions (with greater decreases in cell height only for the lateral femoral condyle cells; p < 0.05) whereas medial femoral and medial tibial plateau cells underwent smaller volume decreases (p < 0.05), due to less deformation in cell height (p < 0.05). Proteoglycan content was reduced in the patellar (p > 0.05), femoral groove, medial femoral condyle and medial tibial plateau experimental sites (p < 0.05). The findings suggest: (i) cell biomechanical responses to cartilage loading in the rabbit knee joint can become altered as early as 3 days after a partial meniscectomy, (ii) are site-specific, and (iii) occur before alterations in tissue mechanics or changes detectable with histology.

Forefoot bending stiffness, running economy and kinematics during overground running

Previous research has shown that altering forefoot (FF) bending stiffness can enhance running economy; however, the mechanism behind the changes in running economy remains unknown. Therefore, the purpose of this study was to investigate the relationship between forefoot bending stiffness, running economy, and lower limb kinematics during overground running. Eighteen aerobically fit recreational male athletes performed overground running using a portable metabolic analysis system to measure oxygen consumption in two footwear conditions with different forefoot bending stiffness. Sagittal plane kinematic data of the metatarsophalangeal, ankle, and knee joints were recorded using a high-speed camera. On average, there was no difference in running economy when running in the Stiff shoe (O2 = 38.1 ± 5.4 mL/kg/min) compared to the Control shoe (O2 = 37.7 ± 5.8 mL/kg/min, p = 0.11). On an individual basis, 10 athletes (Responders) improved their running economy with increased FF bending stiffness (∆O2 = −2.9%), while eight athletes (Non-Responders) worsened or did not improve their running economy in a stiff shoe (∆O2 = +1.0%). In stiff footwear, Responders experienced kinematic changes at the ankle joint (decreased angular velocity) that likely resulted in decreased energy requirement for muscular contractions due to a presumed shift on their individual force–velocity relationship. The lack of improvement in running economy by the Non-Responders may be attributed to a presumed lack of a shift in the force–velocity relationship of the calf musculature. Instead, Non-Responders experienced kinematic changes (increased ankle plantarflexion during push phase with stiff footwear) that likely hindered their moment-generating capability potentially due to a shift on their individual force–length relationship. These findings represent important progress towards explaining inter-individual changes in running economy with different footwear bending stiffness.

Influence of the composition of artificial turf on rotational traction and athlete biomechanics

This study demonstrated that daily use of minimalist footwear could have a beneficial effect on the balance of older adults. Increased hallux strength and reach ability further suggest that walking in minimalist footwear activates the foot muscles to a greater extent, thus leading to improvements in foot strength and consequently balance. Whilst we observed no improvements in postural sway or the gait measures associated with poor balance control, the qualitative data suggest that outside of a laboratory environment improvements have been witnessed in both confidence and balance itself. The participants in this study were habitually very active with good baseline performance thus greater improvements may be seen in the less active amongst this population. The intervention group will be compared to the control group upon completion of data collection.

The influence of gearing footwear on running biomechanics

The influence of nonlinear bending stiffness footwear, which alters the metatarsophalangeal (MTP) joint bending as a function of forefoot bending stiffness, has been postulated to improve athletic performance and reduce injury risk during many sports. As the shoe moves through greater amounts of bending, forefoot stiffness should increase nonlinearly, to shift the centre of pressure forward (improving performance), while restricting forefoot bending in regions where turf toe injury may result. Recently, materials which allow for stiffness modifications as a function of forefoot flexion angle have been developed; however, the efficacy of this technology is unknown. Therefore, the purpose of this project was to evaluate the influence of gearing technology (a variable bending stiffness shoe) on biomechanics during running and sprinting. Ten male recreational athletes performed running and sprinting in two footwear conditions consisting of an altered US 10 adidas 16.4 FXG cleat. The footwear was altered by placing carbon fibre insoles with variable (nonlinear stiffness) into the shoes creating two different conditions: Control (no insole) and the variable stiffness (varStiff) shoe (gearing insoles). Kinematic (joint angles) and kinetic (ground reaction force and 3D joint moments) data of the lower extremity were recorded during each movement. The results of the study indicate that the variable stiffness insoles did positively influence athlete lower extremity biomechanics. At the MTP joint, as running speed increased (and normal MTP bending range of motion increased), the variable stiffness insoles reduced the amount of MTP bending of the shoes and reduced the medial–lateral movement of the point of force application. Additionally, the variable stiffness insoles reduced key biomechanical injury risk variables, such as non-sagittal plane joint loading at the knee and ankle joint.