Purpose: This randomized controlled study assessed whether muscle preconditioning with ischemic exercise can prevent loss of quadriceps femoris volume, strength, and function after anterior cruciate ligament (ACL) reconstruction. Methods: Twenty subjects scheduled for ACL reconstruction with autologous hamstring grafts performed 5 exercise sessions during the last 10 days before surgery. They were randomly assigned into two groups: ISHEMIC – performing low-load ischemic knee-extension exercise with pneumatic tourniquet inflated to 150 mmHg, or SHAM – knee-extension exercise with tourniquet inflated to 20 mmHg. Quadriceps femoris (QF) volume (measured by MRI), maximal voluntary isometric contraction torque, and single-leg anterior reach distance were assessed prior to preconditioning and repeated at 4 and 12 weeks post-surgery. Results: There were no significant differences between the groups in any of the measured variables prior to or after surgery. The deficit in QF vastii volume increased to 20±5 % in ISCHEMIC and 23±10 % in SHAM group at 4 weeks and persisted at 16±4 % in ISCHEMIC and 20±11 % in SHAM group at 12 weeks post-surgery. There were no statistically significant differences in rectus femoris volumes. Likewise, the deficit in QF maximal isometric torque persisted at 15±15 % in ISCHEMIC and 22±16 % in SHAM at 12 weeks post-surgery. There were no significant differences between groups in single-leg reach distance deficit. Conclusions: Muscle preconditioning with short ischemic exercise showed no protective effect on QF muscle mass, isometric strength, or knee functional loss in patients undergoing ACL reconstruction. Moreover, all patients reached similar level of QF muscle atrophy and strength deficit regardless of their pre-operative muscular status.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 4937067INTRODUCTION: Blood flow restricted resistance exercise (BFRRE) is commonly used to gain muscle mass and strength. The most efficient technique of blood-flow restriction for muscle conditioning has not been identified as yet. During rest, width of the tourniquet and limb circumference has been shown to substantially influence pressure distribution to the tissues. Thus the aim of this study was to further optimize tourniquet characteristics for restriction of limb muscles blood flow. METHODS: Newly designed double-compartment tourniquet cuff with asymmetric pressure distribution (DCAP, 14 cm wide) and standard single-compartment tourniquet cuff with symmetric pressure distribution (SCSP, 10 cm wide) were tested on 17 healthy volunteers (27.3±5.2 years) during rest. Thigh circumference and skinfold were determined for each leg. Efficiency of tourniquets was compared bilaterally on proximal thighs at four occlusion pressures (OP = 120, 160, 200 and 240 mmHg). Changes in hemoglobin kinetics in v. lateralis muscle (near-infrared spectroscopy), cardiovascular responses (ECG and ABP), isometric endurance, maximal voluntary isometric contraction (MIVC) torque and pain intensity (visual analogue scale, VAS) were analyzed. RESULTS: Lean thigh circumference did not differ between legs (L= 57.3±3.7 cm, R=57.1±3.8 cm). VAS scores did not differ between tested tourniquets, but did significantly increase (p=0.03) at OP 200 mmHg and higher. Difference (p = 0.009) in slope of total hemoglobin concentration change ([tHbs]) was found between the tourniquets at OP 160 mmHg (DCAP=0.028μM/s, SCSP=0.056μM/s). Mean ABP was significantly increased (p= 0.02) at OP 120 mmHg compared to baseline values, whereas change in heart rate was detected. MIVC did not differ between legs (L= 230 ± 77 Nm, R= 233 ± 77 Nm). Shorter time to exhaustion (-11%; p=0,003) was found in ischemic condition compared to control condition, while no difference was found between tested tourniquets. DISCUSSION: Based on differences in [tHbs], arterial occlusion was induced at OP ≥ 160 mmHg with DCAP, whereas OP ≥ 200 mmHg was required with SCSP. Given that higher pressure may cause damage to underlying tissues and increases discomfort, it is concluded that novel tourniquet design allows safer and more efficient blood flow restriction at a given tourniquet pressure and discomfort during rest. Whether the same is achieved during BFRRE, needs further investigation.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 4936811Skeletal muscle weakness is inevitable negative effect of injury, disease or surgery of joints. Key factors of muscle deconditioning are 1) muscle atrophy and 2) arthrogenic muscle inhibition (AMI); however their interaction and underlying mechanisms are still poorly understood. The AMI peaks few days after injury or surgery; thereafter a minor attenuation takes place which plateaus for up to 6 months. Further and more progressive attenuation of AMI sets in only after this period and is completely abolished within 2 to 4 years after the event. The AMI has been demonstrated to affect Quadriceps Femoris (QF), but is absent in hamstring muscles. However, the role of AMI in development of muscle weakness, especially after ACL injury or reconstruction, remains equivocal. Recent studies showed that muscle atrophy nevertheless attributes more to QF strength deterioration than AMI. Physiotherapeutic modalities aim to reduce one or both key factors of muscle weakness through various physiological pathways. Therefore the efficiency of each modality depends on the primary cause of muscle weakness in a given individual. In case where AMI is predominantly caused by reflex neural inhibition, peripheral neuromuscular electric and magnetic stimulation used in conjunction with voluntary muscle contraction proved efficient. The inhibitory neural inflow from the swollen joint can be attenuated prior to muscle activation by application of criotherapy, TENS or non-loaded continuous movement of the affected joint. If AMI is primarily driven by inhibition of upper motor neurons, transcranial magnetic stimulation of motor cortex has been shown effective, however technical and economic limitations of the modality hinder more widespread clinical use. In case of predominant muscle atrophy, the range of effective modalities is substantially narrowed due to contraindications for standard high-load resistance exercise. Low-load resistance exercise with blood flow restriction in active muscles (ischemic exercise), has been proven as effective alternative to conventional high-load exercise in improving muscle strength and hypertrophy, as well as augmenting muscle endurance and oxygenation. Given that disuse muscle atrophy affects primarily Type I fibres and adjacent muscle capillary network, there is a lot of therapeutic potential in this novel modality. Efficiency and safety of ischemic exercise in various pathologic conditions is currently under investigation worldwide.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 4931179