Is thoracolumbar fascia shear-wave modulus affected by active and passive knee flexion?

The purpose of this study was to examine the effect of passive and active knee flexion efforts on the stiffness of the thoracolumbar (TLF), semitendinosus (STF), and semimembranosus fascia (SMF). Fourteen young healthy males participated in this study. Using ultrasound shear-wave elastography, fascia elastic modulus was measured at rest (passive condition) and during submaximal isometric knee flexion efforts (active condition) with the hip at neutral position and the knee flexed at 0°, 45°, and 90°. Analysis of variance designs indicated that when the knee was passively extended from 90° to 0°, shear modulus of the TLF, SMF, and STF increased significantly (p < 0.05). Similarly, active knee flexion contractions caused a significant increase in TLF, SMF, and STF shear modulus (p < 0.001). Compared to hamstring fascia, the TLF showed greater thickness but a lower shear modulus (p < 0.05) while STF modulus was greater compared that to SMF during active contraction (p < 0.05). These results indicate that exercising the hamstring muscles can remotely influence the stiffness of the fascia which surrounds the lumbar area.

Distal hamstrings tendons mechanical properties at rest and contraction using free-hand 3-D ultrasonography.

Tendon properties impact human locomotion, influencing sports performance, and injury prevention. Hamstrings play a crucial role in sprinting, particularly the biceps femoris long head (BFlh), which is prone to frequent injuries. It remains uncertain if BFlh exhibits distinct mechanical properties compared to other hamstring muscles. This study utilized free-hand three-dimensional ultrasound to assess morphological and mechanical properties of distal hamstrings tendons in 15 men. Scans were taken in prone position, with hip and knee extended, at rest and during 20%, 40%, 60%, and 80% of maximal voluntary isometric contraction of the knee flexors. Tendon length, volume, cross-sectional area (CSA), and anteroposterior (AP) and mediolateral (ML) widths were quantified at three locations. Longitudinal and transverse deformations, stiffness, strain, and stress were estimated. The ST had the greatest tendon strain and the lowest stiffness as well as the highest CSA and AP and ML width strain compared to other tendons. Biceps femoris short head (BFsh) exhibited the least strain, AP and ML deformation. Further, BFlh displayed the highest stiffness and stress, and BFsh had the lowest stress. Additionally, deformation varied by region, with the proximal site showing generally the lowest CSA strain. Distal tendon mechanical properties differed among the hamstring muscles during isometric knee flexions. In contrast to other bi-articular hamstrings, the BFlh high stiffness and stress may result in greater energy absorption by its muscle fascicles, rather than the distal tendon, during late swing in sprinting. This could partly account for the increased incidence of hamstring injuries in this muscle.

Thoracolumbar Fascia and Lumbar Muscle Stiffness in Athletes with A History of Hamstring Injury.

The purpose of this study was to examine the differences in thoracolumbar fascia (TLF) and lumbar muscle modulus in individuals with and without hamstring injury using shear wave elastography (SWE). Thirteen male soccer players without a previous hamstring injury and eleven players with a history of hamstring injury performed passive and active (submaximal) knee flexion efforts from 0°, 45° and 90° angle of knee flexion as well as an active prone trunk extension test. The elastic modulus of the TLF, the erector spinae (ES) and the multifidus (MF) was measured using ultrasound SWE simultaneously with the surface electromyography (EMG) signal of the ES and MF. The TLF SWE modulus was significantly (p < 0.05) higher in the injured group (range: 29.86 ± 8.58 to 66.57 ± 11.71 kPa) than in the uninjured group (range: 17.47 ± 9.37 to 47.03 ± 16.04 kPa). The ES and MF modulus ranged from 14.97 ± 4.10 to 66.57 ± 11.71 kPa in the injured group and it was significantly (p < .05) greater compared to the uninjured group (range: 11.65 ± 5.99 to 40.49 ± 12.35 kPa). TLF modulus was greater than ES and MF modulus (p < 0.05). Active modulus was greater during the prone trunk extension test compared to the knee flexion tests and it was greater in the knee flexion test at 0° than at 90° (p < 0.05). The muscle EMG was greater in the injured compared to the uninjured group in the passive tests only (p < 0.05). SWE modulus of the TLF and ES and MF was greater in soccer players with previous hamstring injury than uninjured players. Further research could establish whether exercises that target the paraspinal muscles and the lumbar fascia can assist in preventing individuals with a history of hamstring injury from sustaining a new injury.

Recovery of kicking kinematics and performance following repeated high-intensity running bouts in the heat: Can a rapid local cooling intervention help young soccer players?

The effects of a cooling strategy following repeated high-intensity running (RHIR) on soccer kicking performance in a hot environment (>30ºC) were investigated in youth soccer players. Fifteen academy under-17 players participated. In Experiment 1, players completed an all-out RHIR protocol (10×30 m, with 30s intervals). In Experiment 2 (cross-over design), participants performed this running protocol under two conditions: (1) following RHIR 5 minutes of cooling where ice packs were applied to the quadriceps/hamstrings, (2) a control condition involving passive resting. Perceptual measures [ratings of perceived exertion (RPE), pain and recovery], thigh temperature and kick-derived video three-dimensional kinematics (lower limb) and performance (ball speed and two-dimensional placement indices) were collected at baseline, post-exercise and intervention. In Experiment 1, RHIR led to small-to-large impairments (p < 0.03;d = -0.42--1.83) across perceptual, kinematic and performance measures. In experiment 2, RPE (p < 0.01; Kendall's W = 0.30) and mean radial error (p = 0.057; η2 = 0.234) increased only post-control. Significant small declines in ball speed were also observed post-control (p < 0.05; d = 0.35). Post-intervention foot centre-of-mass velocity was moderately faster in the cooling compared to control condition (p = 0.04; d = 0.60). In youth soccer players, a short cooling period was beneficial in counteracting declines in kicking performance, in particular ball placement, following intense running activity in the heat.

Effect of Bridge Exercise Duration on Lateral Abdominal Muscle Thickness and Gluteus Maximus Activation.

CONTEXT: Bridge exercises are extensively used in trunk-strengthening programs. The aim of this study was to investigate the effect of bridging duration on lateral abdominal muscle thickness and gluteus maximus activation. DESIGN: Cross-sectional. METHODS: Twenty-five young males participated in this study. Transversus abdominal (TrA), external and internal oblique ultrasound thickness, gluteus maximus electromyographic activation, and sacral tilt angle were simultaneously measured for every second during 30-second bridging exercise. The contraction thickness ratio and root mean squared signal (normalized to maximum isometric contraction signal) during 6 exercise durations (from 0 to 5, 10, 15, 20, 25, and 30 s) were also calculated and compared using analysis of variance designs. RESULTS: TrA and internal oblique contraction thickness ratio and gluteus maximus root mean squared increased during the first 8 to 10 seconds and remained elevated until the end of the 30-second exercise (P < .05). External oblique contraction thickness ratio declined during exercise (P < .05). Five-second bridging showed less TrA thickness and anteroposterior and mediolateral sacral tilt angle and a lower anteroposterior tilt variability compared with bridges, which lasted more than 10 seconds (P < .05). CONCLUSIONS: Bridge exercises longer than 10 seconds may be better for promoting TrA recruitment than bridges of shorter duration. Clinicians and exercise specialists could adjust the duration of bridge exercise based on the aims of the exercise program.

Alternating or Bilateral Exercise Training does not Influence Force Control during Single-Leg Submaximal Contractions with the Dorsiflexors.

The aim of the study was to assess the influence of habitual training history on force steadiness and the discharge characteristics of motor units in tibialis anterior during submaximal isometric contractions. Fifteen athletes whose training emphasized alternating actions (11 runners and 4 cyclists) and fifteen athletes who relied on bilateral actions with leg muscles (7 volleyball players, 8 weight-lifters) performed 2 maximal voluntary contractions (MVC) with the dorsiflexors, and 3 steady contractions at 8 target forces (2.5%, 5%, 10%, 20%, 30%, 40%, 50% and 60% MVC). The discharge characteristics of motor units in tibialis anterior were recorded using high-density electromyography grids. The MVC force and the absolute (standard deviation) and normalized (coefficient of variation) amplitudes of the force fluctuations at all target forces were similar between groups. The coefficient of variation for force decreased progressively from 2.5% to 20% MVC force, then it plateaued until 60% MVC force. Mean discharge rate of the motor units in tibialis anterior was similar at all target forces between groups. The variability in discharge times (coefficient of variation for interspike interval) and the variability in neural drive (coefficient of variation of filtered cumulative spike train) was also similar for the two groups. These results indicate that athletes who have trained with either alternating or bilateral actions with leg muscles has similar effects on maximal force, force control, and variability in the independent and common synaptic input during a single-limb isometric task with the dorsiflexors.

Ankle Angle but Not Knee Angle Influences Force Fluctuations During Plantar Flexion.

The purpose of the study was to evaluate the influence of changes in ankle- and knee-joint angles on force steadiness and the discharge characteristics of motor units (MU) in soleus when the plantar flexors performed steady isometric contractions. Submaximal contractions (5, 10, 20, and 40% of maximum) were performed at two ankle angles (75° and 105°) and two knee angles (120° and 180°) by 14 young adults. The coefficient of variation of force decreased as the target force increased from 5 to 20% of maximal force, then remained unaltered at 40%. Independently of knee angle, the coefficient of variation for force at the ankle angle of 75° (long length) was always less (p<0.05) than that at 105° (shorter length). Mean discharge rate, discharge variability, and variability in neural activation of soleus motor units were less (p<0.05) at the 75° angle than at 105°. It was not possible to record MUs from medial gastrocnemius at the knee angle of 120° due to its minimal activation. The changes in knee-joint angle did not influence any of the outcome measures. The findings underscore the dominant role of the soleus muscle in the control of submaximal forces produced by the plantar flexor muscles.

Muscle injury characteristics and incidence rates in men's amateur soccer: A one season prospective study.

The objectives of the study were to examine the incident rate (IR), characteristics, and mechanisms of muscle injuries of 121 men amateur soccer players that voluntarily participated in this project. Sixty-five muscle injuries with an overall IR of 3.62/1000 h, 95% CI 2.7-4.5, were reported. The most frequently injured muscle groups were the hamstrings (IR 1.78/1000 h, 95% CI 1.1-2.3), followed by the adductors (IR 1.5/1000 h, 95% CI 0.93-2.06). Most muscle injuries were characterized as mild (IR 2.3/1000 h, 95% CI 1.53-2.92) or minimal (IR 1.28/1000 h, 95% CI 1.16-2.39. Higher incidence of injury sustained during matches (IR 14.09 injuries/1000 h, 95% CI 9.49-18.7), than in training (IR 1.88 injuries/1000 h, 95% CI 1.19-2.56). The most frequent injury mechanisms were high-speed running (84.4%) and change of direction (44.4%), for hamstring and adductors-related groin injuries, respectively. Players aged over 24 years had a 7-fold increased risk to sustain a hamstring injury but a lower risk to sustain an adductor-related groin injury. Injury prevention and rehabilitation management strategies may reduce muscle injury rates in amateur soccer.

Hamstring to quadriceps strength ratio and cross-sectional area of the quadriceps and hamstrings muscles assessed using extended field-of-view ultrasonography.

This study examined whether the association between hamstring (H) and quadriceps (Q) strength with size depends on the region and the muscle used to examined cross-sectional area (CSA). Maximum isometric contraction knee extension and flexion torque was obtained from 20 young participants while Q and H CSA was recorded using extended field of view ultrasonography at four sections along the thigh. Stepwise linear regression models using the maximum CSA of individual muscles showed a significant association of quadriceps (R2 = 0.793) and hamstring (R2 = 0.275) CSA with MVC torque (p < 0.05). The association was lower when maximum or section-specific muscle group CSAs were used as indices of size. The H:Q CSA ratio showed a significant association (R2 = 0.275, p < 0.05) and a moderate correlation (r = 0.48) with H:Q torque ratio. These results indicated that the association between muscle CSA and strength differs between the knee extensors and flexors. Amongst the various indices of muscle size, the combination of maximum CSA values of each muscle displayed the greatest relationship between strength and CSA. The H:Q CSA ratio can explain a significant but small part of the H:Q isometric strength ratio.

Women with knee osteoarthritis increase knee muscle co-contraction to perform stand to sit.

BACKGROUND: There is lack of sufficient research evidence when we examine how knee osteoarthritis (OA) affects performance of stand to sit, a very important task for daily function. AIM: The aim of this study was to investigate if women with unilateral knee OA perform the stand to sit task in the same way as healthy adults of the same age. METHODS: Fifteen women with knee OA (age 64.05 ± 4.23 years, height 161.52 ± 5.03 cm, and mass 75.23 ± 8.51 kg) and fifteen healthy subjects of the same age (age 62.13 ± 4.15 years, height 160.73 ± 5.10 cm, and mass 75.20 ± 9.87 kg) volunteered to participate. The experimental task required sitting to a chair starting from a bipedal standing position. Electromyographic activity of the vastus lateralis and biceps femoris was examined for both legs. In addition, joint kinematics of the lower limb and vertical ground reaction forces were recorded bilaterally. RESULTS: Movement duration was not different between the groups. Women with knee OA showed significantly lower vastus lateralis activation and higher knee muscle co-contraction of the affected leg compared to the same leg of the control group. In addition, they had smaller knee range of motion for both legs compared to the control group participants. CONCLUSION: Knee muscle co-contraction is employed by women with knee OA to perform the stand to sit movement at the same duration as their healthy counterparts. This compensatory mechanism may be important for the task execution, but at the same time, it can be harmful for the joint.

Effects of Exercise and an Integrated Neuromuscular Inhibition Technique Program in the Management of Chronic Mechanical Neck Pain: A Randomized Controlled Trial.

OBJECTIVE: The aim of this study was to evaluate the effect of adding the integrated neuromuscular inhibition technique (INIT) to therapeutic exercise (TE) in individuals with chronic mechanical neck pain (CMNP). METHODS: In this 34-week, assessor-blind randomized controlled trial, 40 participants (men and women) with CMNP with active or latent myofascial trigger points on the neck muscles were divided into 2 groups. The participants followed 4 treatments per week for 10 weeks. The intervention group followed a TE program in combination with the INIT, whereas the control group followed the same program without the INIT. Both protocols were applied by physiotherapists. Pain, disability, pressure pain threshold, active range of motion, and health-related quality of life were evaluated before, during, and after the intervention, whereas patients were followed for 6 months after completion of treatment. Repeated-measures ANOVA was applied. RESULTS: Both groups showed a significant improvement in all dependent measures after the intervention (P < .05). However, the intervention group showed greater improvement in the visual analog scale and neck disability index score, in the neck muscles pressure pain threshold, in the range of motion, and in the 36-Item Short Form Health Survey score, than the control group. In many of the above variables this improvement was seen from the second week and was maintained for 6 months after the intervention. CONCLUSION: The results of this preliminary study suggest that the addition of the INIT to a TE program had a positive effect on pain, functionality, and the quality of life in individuals with CMNP.

The Effect of Additional External Resistance on Inter-Set Changes in Abdominal Muscle Thickness during Bridging Exercise.

Bridging exercises with abdominal hollowing are often used as a regimen for improving spinal stability. Lately, this type of training has become very popular among elite athletes, creating a need for more demanding exercises. The purpose of this study was to investigate whether the use of additional external resistance is beneficial for abdominal muscle recruitment during bridge exercise. Tissue movement of the transversus abdominis (TrA) and the rectus abdominis (RA) was recorded with the use of two synchronized ultrasonic devices, in 20 healthy college students. From the hook-lying position participants were examined in eight different exercise conditions: a) rest, b) abdominal drawing-in maneuver (ADIM), c) bridge, d) bridge- ADIM, e) bridge with 10KG, f) bridge- ADIM with 10KG, g) bridge with 20KG and h) bridge-ADIM with 20KG. Analysis of variance (ANOVA) showed a statistically significant increase in TrA thickness when performing the bridge exercise combined with ADIM compared to rest mode (p < .05). RA thickness decreased when the ADIM was performed, compared to rest (p < 0.05). No significant difference in TrA and RA thickness when exercising with and without external resistance was observed (p > 0.05). The main outcome of this study was that external loading provided some extra level of difficulty, yet it was not beneficial for abdominal muscle recruitment, when performing a supine bridge exercise.

Antagonist muscle architecture and aponeurosis/tendon strain of biceps femoris long head during maximal isometric efforts.

INTRODUCTION: Examination of the mechanical behavior of the hamstrings when acting as antagonists provides information about loading of this muscle group and its role for joint stability during forceful quadriceps contractions. The aim of this study was to quantify biceps femoris long head fascicle length (FL), angle of pennation (PA) and distal tendon/aponeurosis strain during maximum voluntary contraction efforts of the knee extensors using real-time ultrasound. METHODS: Fourteen participants performed passive joint movements and maximum voluntary knee extension and flexion efforts of the knee flexors at 0°, 45° and 90° of knee flexion. An ultrasound probe was used to visualize FL, PA and tendon/aponeurosis strain from the distal part of the muscle. RESULTS: Two-way analysis of variance designs indicated that: (a) antagonist BFlh tendon/aponeurosis strain increased significantly up to 2.77 ± 1.25% relative to rest (p < 0.05). The FL increased non-significantly (2.86 ± 6.81%) while the PA was unaltered during isometric MVC efforts of the knee extensors (p > 0.05) (b) FL, PA and tendon/aponeurosis strain of the BFlh when acting as antagonist were not significantly affected by knee joint angular position (p > 0.05). CONCLUSIONS: Antagonist hamstring function takes the form of a lengthened tendon/aponeurosis, no fascicle shortening and submaximal neural activation. Future research could examine whether exercise interventions that aim to alter tendon/aponeurosis mechanical properties of the hamstrings when acting as antagonists are beneficial for injury prevention and rehabilitation.

Use of Ultrasound to Monitor Biceps Femoris Mechanical Adaptations after Injury in a Professional Soccer Player.

This study examined the use of ultrasound to monitor changes in the long head of the biceps femoris (BF) architecture of aprofessional soccer player with acute first-time hamstring strain. The player followed a 14 session physiotherapy treatment until return to sport. The pennation angle and aponeurosis strain of the long head of the biceps femoris (BF) were monitored at 6 occasions (up until 1 year) after injury. The size of the scar / hematoma was reduced by 63.56% (length) and 67.9% (width) after the intervention and it was almost non-traceable one year after injury. The pennation angle of the fascicles underneath the scar showed a decline of 51.4% at the end of the intervention while an increase of 109.2% of the fascicles which were closer to deep aponeurosis was observed. In contrast, pennation angle of fascicles located away from the injury site were relatively unaffected. The treatment intervention resulted in a 57.9% to 77.3% decline of maximum strain per unit of MVC moment and remained similar one year after the intervention. This study provided an example of the potential use of ultrasound-based parameters to link the mechanical adaptations of the injured muscle to specific therapeutic intervention. Key pointsChanges in fascicle orientation after biceps femoris mild tear were reduced after a 28 day intervention and remained similar one year after injury.Tendon/aponeurosis strain per unit of moment of force decreased during the course of the therapeutic intervention.Future studies could utilize ultrasonography to monitor mechanical responses after various types of hamstring injury and interventions in order to improve criteria for a safe return to sport.

Post-activation potentiation: The neural effects of post-activation depression.

INTRODUCTION: Our knowledge of the neurophysiology of post-activation potentiation (PAP) is limited. The purpose of this study was to examine the effect of PAP on twitch torque and H-reflex amplitude after a 10-s maximal voluntary contraction (MVC). METHODS: PAP measurements were assessed with the plantarflexors in a relaxed state and during a tonic contraction at 10% MVC. RESULTS: The H-reflex/maximum M-wave ratio (H/M) decreased significantly (P<0.05) and returned to baseline levels after 1 min. The decrement in H/M was depressed when the plantarflexors were active at 10% MVC, and the depression was more obvious in the lateral gastrocnemius than in the soleus muscle. CONCLUSIONS: The inhibition induced immediately after contraction could be attributed to post-activation depression. We conclude that PAP after a 10-s MVC cannot be attributed to increased motor neuron excitability through the reflex pathway as assessed by the H-reflex technique.

Reliability of Single-leg and Double-leg Balance Tests in Subjects with Anterior Cruciate Ligament Reconstruction and Controls.

The purpose of this study was to assess the test-retest reliability of postural balance in patients with anterior cruciate ligament reconstruction (ACL) and controls. Ten healthy subjects and 15 individuals with ACL reconstruction performed single-leg and double-leg balance tests. The center of pressure (COP) was recorded using a pressure platform. For the total COP path, the intraclass correlation coefficient (ICC) ranged from 0.79 to 0.91. For the COP standard deviation, the ICCs ranged from 0.68 to 0.94. For the COP velocity, the ICCs ranged from 0.72 to 0.91. The sway area and ellipse scores displayed ICCs values of 0.67 to 0.95 and 0.53 to 0.92, respectively. The ICCs were higher for double leg tests compared with single-stance ones. These results indicate that 30 s balance tests in double and single-leg stance are reliable tools to assess static balance. The use of such tests to monitor rehabilitation programs following ACL reconstruction is recommended.

A Comparison between Core Stability Exercises and Muscle Thickness Using Two Different Activation Maneuvers.

Core stability training is crucial for competitive athletes, individuals who want to improve their health and physical performance, and those undergoing clinical rehabilitation. This study compared the ultrasound (US) muscle thickness of the abdominals and lumbar multifidus (LM) muscles between seven popular trunk stability exercises performed using hollowing and bracing maneuvers. Forty-four healthy young adults, aged between 21 and 32 years, performed a plank, bird dog, beast crawl, dead bug, Pilates tap, bridge, and side planks using the bracing and the hollowing maneuver. The thickness of the transversus abdominis (TrA), internal oblique (IO), and LM muscles was measured simultaneously using two ultrasound machines. Analysis of variance designs indicated that during hollowing, the bird dog and side plank exercises resulted in the greatest increase in the muscle's relative thickness overall. The relative thickness of all muscles was significantly greater (p < 0.001) during hollowing (22.7 ± 7.80 to 106 ± 24.5% of rest) compared to bracing (18.7 ± 7.40 to 87.1 ± 20.9% of rest). The TrA showed the greatest increase in thickness (p < 0.001) compared to the IO and LM. Additionally, the IO had a greater increase in thickness (p < 0.001) than the LM. In conclusion, our findings indicate that the bird dog and side plank exercises, when performed with hollowing, showed the most significant total muscle thickness increase. Notably, the hollowing maneuver enhances the thickness of the TrA, IO, and LM muscles more than the bracing maneuver. This contributes to the discussion on optimal strategies for dynamic core stabilization.

Does Pelvic Tilt Angle Influence the Isokinetic Strength of the Hip and Knee Flexors and Extensors?

The purpose of this study was to examine the effect of pelvic tilt angle on maximum hip and knee muscles' strength and antagonist/agonist strength ratios. Twenty-one young males and females performed maximum isokinetic concentric knee extension-flexion and hip extension-flexion efforts at 60°·s-1, 120°·s-1, and 180°·s-1 from three positions: anterior, neutral, and posterior pelvic tilt. Peak torques and knee flexor-to-extensor and hip flexor-to-extensor torque ratios were analyzed. An analysis of variance showed that peak hip extensor torque was significantly greater in the anterior pelvic tilt condition compared to either neutral or posterior pelvic tilt angles (p > 0.05). No effects of changing pelvic tilt angle on hip flexor, knee flexor, or knee extension values were found (p > 0.05). The hip flexor-to-extensor torque ratio decreased (p < 0.05) in the anterior pelvic tilt position relative to the other positions, while no difference in the knee flexor-to-extensor ratio between pelvic positions was observed (p > 0.05). This study shows that an increased anterior pelvic tilt affects the maximum isokinetic strength of the hip extensors, supporting previous suggestions regarding the link between pelvic position and hip and knee muscle function. Isokinetic testing from an anterior pelvic tilt position may alter the evaluation of hip flexion/extension strength.

Paraspinal Muscle Stiffness during Hamstring Exercise Using Shear-Wave Elastography.

Soccer teams integrate specific exercises into their typical workout programs for injury prevention. This study examined the effects of hamstring exercise on paraspinal and hamstring stiffness. These findings can inform training and rehabilitation programs to improve muscle health and prevent injuries. Fifteen young, healthy males performed passive and active (submaximal) knee flexion efforts from 0°, 45°, to 90° angle of knee flexion from the prone position. Using shear-wave elastography (SWE) and surface electromyography, we measured the elastic modulus and root mean square (RMS) signal of the erector spinae (ES), multifidus (MF), semitendinosus (ST), and semimembranosus (SM) during different knee flexion angles. Passive SWE modulus at 0° was 12.44 ± 4.45 kPa (ES), 13.35 ± 6.12 kPa (MF), 22.01 ± 4.68 kPa (ST), and 21.57 ± 5.22 kPa (SM) and it was greater (p < 0.05) compared to 45° and 90°. The corresponding values during knee flexion contractions at 0° increased to 18.99 ± 6.11 kPa (ES), 20.65 ± 11.31 kPa (MF), 71.21 ± 13.88 kPa (ST), and 70.20 ± 14.29 kPa (SM) and did not differ between angles (p > 0.05). Compared to rest, the relative increase in the SWE modulus during active contraction had a median value (interquartile range) ranging from 68.11 (86.29) to 101.69 (54.33)% for the paraspinal muscles and it was moderately to strongly correlated (r > 0.672) with the corresponding increase of the hamstring muscles [ranging from 225.94 (114.72) to 463.16 (185.16)%]. The RMS signal was greater during active compared to passive conditions, and it was lower at 90° compared to 45° (for SM/ST) and 0° (for all muscles). The association between paraspinal and hamstring passive muscle stiffness indicates a potential transmission of forces through myofascial connections between the lumbar spine and the lower limbs. In this laboratory setting, hamstring exercises affected the stiffness of the paraspinal muscles.

Mid-vastus approach induces milder short-term effects on postural control compared to parapatellar approach in total knee arthroplasty.

BACKGROUND: Mid-Vastus and Medial Parapatellar techniques are used for total knee arthroplasty. Their short-term effects within the first month after surgery are yet unexplored. The purpose of this study was to compare Mid-Vastus and Medial Parapatellar effects on knee strength and balance control, at 5 days, 2 weeks and one month after surgery. It was hypothesized that Mid-Vastus would induce milder effects on the dependent variables due to its less invasive nature. METHODS: Twenty females, randomly assigned to either the Mid-Vastus or the Medial Parapatellar group performed knee flexion-extension force and 30 s of bipedal stance before, 5 days, 2 weeks and one month after surgery. Maximum force, weight distribution and travel distance of the Center of Pressure were calculated. FINDINGS: Both groups showed decreased force output at all post-measurements compared to before surgery. Medial Parapatellar group showcased significantly higher travel distance at the 2 weeks measurement (Z = -2.268, p = .023, |r| = 0.507) compared to before surgery. This result was also imprinted on the travel distance of the non-surgical knee limb in the post (t = 3.259, p = .004, d = 1.456), 2 weeks (Z = -2.570, p = .009, |r| = 0.574) and one month measurement (t = 2.653, p = .016, d = 1.185). INTERPRETATION: While force is affected for both approaches, Mid-Vastus approach does not affect postural control. Therefore, Mid-Vastus is a less invasive technique compared to Medial Parapatellar. This work highlights the differences between Mid-Vastus and Medial Parapatellar approaches at least until the first month of rehabilitation.