Collagen is a key component of the extracellular matrix in a variety of tissues and hence is widely used in tissue engineering research, yet collagen has had limited uptake in the field of 3D printing. In this study we successfully adapted an existing electronic printing method, aerosol jet printing (AJP), to print high resolution 3D constructs of recombinant collagen type III (RHCIII). Circular samples with a diameter of 4.5mm and 288 layers thick, or a diameter of 6.5mm and 400 layers thick were printed on glass cover slips with print lines of 60µm. Attenuated Total Reflectance Fourier-Transorm Infa-red (ATR-FTIR) spectroscopy performed on the 4 of the printed samples and dried non-printed RHCIII samples showed that no denaturation had occurred due to the printing process. Printed samples were crosslinked using EDC [N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride, Sigma Aldrich] to improve their stability and mechanical strength. Differential scanning calorimetry (DSC) performed showed a marked difference in the denaturation temperature between crosslinked printed samples and fibrillar non-printed samples and nano-indentation showed that the construct was relatively stiff. Previous results with similar samples have shown that mesenchymal stem cells (MSCs) align with and travel parallel to print direction. Results obtained from these samples show signs that they might be applied in other areas such as bone tissue engineering.
Strengthening the lumbar extensor musculature is a common recommendation for CLBP. Although reported as effective, variability in response in CLBP populations is not well investigated. This study investigated variability in responsiveness to isolated lumbar extension (ILEX) resistance training in CLBP participants by retrospective analysis of 3 RCTS. Data from 77 intervention participants was available (males = 43, females = 34) 37 control participants (males = 20, females = 17). Intervention participants all underwent 12wks of ILEX resistance training and changes in ILEX strength, pain (VAS) and disability (ODI) measured. True inter-individual response variability was examined through calculation of difference in the standard deviation of change scores for both control and intervention. Intervention participants were classified into using Purpose and Background
Methods and Results
The co-ordinated contraction of the kinetic chain is responsible for the dissipation of force. Weakness in the kinetic chain, such as the posterior oblique sling (POS), may increase the demand on additional muscles, such as the hamstrings, to compensate. The lumbar extensors may be particularly vulnerable in the kinetic chain, as they appear difficult to strengthen due to the dominant hip extensors. Therefore, this study aimed to investigate whether participants with a history of hamstring injuries presented with low back pain because of greater deficits in lumbar extensor strength, and impaired co-ordination of the POS. Twenty male footballers were recruited (n: Injured- 9, Controls- 11). Isolated lumbar extension strength, low back pain, and the contraction time of muscles within the POS during a hip extension test were recorded. Participants were then grouped in either the injury or control group.Background & Purpose
Methods
The level of hamstring antagonist activation is thought to be related to knee functionality following anterior cruciate ligament (ACL) injury/surgery as pronounced co-activation can control anterior tibial translation (ATT). The purpose of this study was to examine relationships between knee functionality and hamstring antagonist activation during isokinetic knee extension in ACL deficient (ACLD) and ACL reconstructed (ACLR) patients. Knee functionality was rated using the Cincinnati Knee Rating System for the involved limb of 10 chronic, functional ACLD patients and 27 ACLR patients (14 using a patella tendon (PT) graft and 13 using a semitendinosus/gracilis tendon (STGT) graft). Each subject also performed maximal effort isokinetic knee extension and flexion at 180°. s-1 for the involved limb with electromyographic (EMG) electrodes attached to the semitendinosus (ST) and biceps femoris (BF) muscles. Antagonist activity of the ST and BF muscles was calculated in 10° intervals between 80-10° knee flexion. For the ACLD group, Pearson product moment correlations revealed significant (p<0.05) moderate, positive relationships between knee functionality and ST and BF antagonist activity across the majority of the knee flexion intervals. For both ACLR groups, several significant (p<0.05) moderate, negative associations were found between ST and BF antagonist activity and knee functionality. Amplified hamstring antagonist activity in ACLD patients at flexion angles representative of those at footstrike and deceleration improves knee functionality as increased crossbridge formation increases hamstring stiffness and decreases ATT. Lower-level hamstring activation is sufficient to unload the ACL graft and improve knee functionality in ACLR patients.
