Relationship between lower limb EMG activity and knee frontal plane projection angle during a single-legged drop jump

ObjectivesTo assess a relationship between lower limb muscle activity and the frontal plane knee kinematics during a single-legged drop jump.DesignCorrelation study;SettingFunctional Anatomy Laboratory.Participants35 healthy collegiate male athletes.Main outcome measuresMuscle activity (%MVIC) of gluteus maximus, gluteus medius, biceps femoris, semitendinosus, vastus medialis quadriceps, vastus lateralis quadriceps, medial gastrocnemius and lateral gastrocnemius; peak knee frontal plane projection angle; and Pearson's correlation coefficients between muscle activity and peak knee frontal plane projection angle. All outcomes were assessed for both dominant and non-dominant limbs.ResultsSignificant correlations (r = 0.46–0.60, P < 0.05) were found between the muscle activities of the gluteus maximus, gluteus medius, biceps femoris, and semitendinosus, when compared to the knee frontal plane projection angle.ConclusionGluteal muscles and hamstring muscles are associated with the peak knee frontal plane projection angle during a single-legged drop jump test. Thus, gluteal and hamstring muscle activities should be considered when developing rehabilitation or injury prevention programs.     

Normal values for hip muscle strength and range of motion in elite,sub-elite and amateur male field hockey players

ObjectivesTo determine normal values for hip strength and range of motion (ROM) of elite, sub-elite and amateur male field hockey players and to examine the effect of age, leg dominance, playing position, playing level and non-time-loss groin pain on hip strength and ROM.DesignCross-sectional study.SettingPhysical testing took place at field hockey clubs.ParticipantsMale field hockey players competing in the three highest Dutch field hockey leagues (n = 104).Main outcome measuresEccentric adduction, eccentric abduction, adductor squeeze strength, adduction/abduction ratio, internal rotation, external rotation and bent knee fall out (BKFO).ResultsStrength and ROM values (mean ± standard deviation) were: adduction = 2.8 ± 0.4 Nm/kg, abduction = 2.6 ± 0.4 Nm/kg, adduction/abduction ratio = 1.1 ± 0.2, squeeze test = 4.5 ± 0.8 N/kg, internal rotation = 34° ± 11°, external rotation = 47° ± 9°, BKFO = 15 ± 4 cm. Age, leg dominance, playing position, playing level and non-time-loss groin pain had no effect on these profiles.ConclusionsNormal values were established for hip strength and ROM of male field hockey players and showed to be independent of age, leg dominance, playing position, playing level and non-time-loss groin pain.     

Effect of knee joint angle on neuromuscular activation of the vastus intermedius muscle during isometric contraction

The purpose of this study was to compare the relationship between surface electromyography (EMG) and knee joint angle of the vastus intermedius muscle (VI) with the synergistic muscles in the quadriceps femoris (QF) muscle group. Fourteen healthy men performed maximal voluntary contractions during isometric knee extension at four knee joint angles from 90°, 115°, 140°, and 165° (180° being full extension). During the contractions, surface EMG was recorded at four muscle components of the QF muscle group: the VI, vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) muscles. The root mean square of the surface EMG at each knee joint angle was calculated and normalized by that at a knee joint angle of 90° for individual muscles. The normalized RMS of the VI muscle was significantly lower than those of the VL and RF muscles at the knee joint angles of 115° and 165° and those of the VL, VM, and RF muscles at the knee joint angle of 140° (P<0.05). The present results suggest that the neuromuscular activation of the VI muscle is regulated in a manner different from the alteration of the knee joint angle compared with other muscle components of the QF muscle group.     

The immediate effect of foot orthoses on gluteal and lower limb muscle activity during overground walking in healthy young adults

BackgroundAlthough foot orthoses are often used in the management of lower limb musculoskeletal conditions, their effects on muscle activation is unclear, especially in more proximal segments of the lower limb.Research questionPrimary aim: Is there an immediate effect of foot orthoses on gluteal muscle activity during overground walking in healthy young adults? Secondary aim: Is there an immediate effect of foot orthoses on the activity of hamstring, quadriceps and calf muscles?MethodsIn eighteen healthy young adults, muscle activity was recorded using fine wire electrodes for gluteus minimus (GMin; anterior, posterior) and gluteus medius (GMed; anterior, middle, posterior); and surface electrodes for gluteus maximus (GMax), hamstring, quadriceps and calf muscles. Participants completed six walking trials for two conditions; shoe and shoe with prefabricated foot orthoses. Muscle activity was normalised to the peak activity of the shoe condition and analysed using one-dimensional statistical non-parametric mapping to identify differences across the gait cycle.ResultsActivity of GMed (anterior, middle, posterior) and GMin (posterior) was reduced in early stance phase when the orthosis was worn in the shoe (p < 0.05). GMin (anterior) activity was significantly reduced during swing (p < 0.05). Muscle activity was also significantly reduced during the orthoses condition for the lateral hamstrings and calf muscles (p < 0.05).SignificanceUsing foot orthoses may provide a strategy to reduce demand on GMin, GMed, lateral hamstring and calf muscles while walking.     

Joint moments of force and quadriceps muscle activity during squatting exercise

The relationship between hip and knee joint load and quadriceps muscle activity during squatting exercise to different depths was studied. Eight young national class Olympic weightlifters performed squatting exercise to 4 different knee flexion angles; 45°, 90°, parallel and deep squats. They held a barbell across their shoulders with a weight of 65% of their one-repetition maximum. The loading moments of force about the hip and knee joints were calculated using a semidynamic method. Video was used for motion recording and electromyograhy for recording activity from die vastus lateralis, rectus femoris and biceps femoris muscles. The loading moment on the hip joint increased significantly from the 90° squat to the parallel, but there was no difference between the parallel and the deep. For the knee joint, there was no difference between the 45°, 90° and parallel, but for the deep squat the loading moment increased significantly. The muscular activity generally increased with increasing squatting depth, but mere were only minor insignificant differences between the parallel and the deep squats. We conclude that knee joint load can be limited by doing parallel instead of deep squats and that this will not decrease quadriceps muscle activity. To limit hip moment, the squat should not be deeper than 90°.     

Relationship between electromyographic activity of knee joint muscles with vertical and posterior ground reaction forces in anterior cruciate ligament reconstructed patients during a single leg vertical drop landing task

ABSTRACT

The objective of the present study is to examine the relation between activity patterns of knee joint muscles with vertical and posterior ground reaction forces (VGRF and PGRF, respectively) in patients after anterior cruciate ligament reconstruction (ACLR). Twenty males post-ACLR participated in this cross-sectional study. The association between muscle activity with VGRF and PGRF was assessed during a single leg vertical drop-landing task. There were strong negative associations between preparatory VL, VM and MG activity and PGRF (P< 0.05). Strong positive associations were found between reactive VM and LH activity with PGRF (P< 0.05). Preparatory co-activation of VM: MH had significant negative associations with VGRF (P< 0.05) and reactive co-activation of VL:LH had a significant positive relation with PGRF(P< 0.05). Greater preparatory activity and co-activation of knee muscles were associated with lower peak PGRF and VGRF, whereas greater reactive activity and co-activation of knee muscles was associated with greater peak PGRF and VGRF. According to our findings, both activity and co-activation of knee muscles during the preparatory phase were associated with reduced PGRF and VGRF, respectively in ACLR patients; thus, incorporating exercises in order to increase preparatory activity and co-activation of knee joint muscles into rehabilitation programs in ACLR patients seems necessary.     

“Dynamic knee valgus” – Are we measuring what we think we’re measuring? An evaluation of static and functional knee calibration methods for application in gait and clinical screening tests of the overhead squat and hurdle step

Background"Dynamic knee valgus” has been identified as a risk factor for significant knee injuries, however, the limits and sources of error associated with existing 3D motion analysis methods have not been well established.Research questionWhat effect does the use of differing static and functional knee axis orientation methods have on the observed knee angle outputs for the activities of gait, overhead squatting and a hurdle step?MethodsA pre-existing dataset collected from one season (September 2015–May 2016) as part of a prospective observational longitudinal study was used. A secondary analysis of data for 24 male footballers, from a single British University football team, was conducted in order to evaluate the effect of static (conventional gait model) and dynamic (constrained and unconstrained mDynaKAD) methods on knee joint kinematics for flexion-extension and valgus-varus angles.ResultsNo single calibration method consistently achieved both the highest flexion and lowest valgus angle for all tests. The constrained and unconstrained mDynaKAD methods achieved superior alignment of the knee medio-lateral axis compared to the conventional gait model, when the movement activity served as its own calibration. The largest mean difference between methods for sagittal and coronal plane kinematics was less than 4° and 14° respectively. Cross-talk could not account for all variation within the results, highlighting that soft tissue artefact, associated with larger muscle volumes and movements, can influence kinematics results.SignificanceWhen considering the trade-off between achieving maximum flexion and minimal valgus angle, the results indicate that the mDynaKAD methods performed best when the selected movement activity served as its own calibration method for all activities. Clinical decision making processes obtained through use of these methods should be considered in light of the model errors associated with cross-talk and effect of soft tissue artefact.     

EMG activity of the iliopsoas muscle and leg kinetics during the soccer place kick

The purpose of the study was to develop a method to record intramuscular electromyogram (EMG) from the iliopsoas muscle and to relate this activity to the kinetics during the soccer place kick. Seven skilled soccer players performed 3 maximal velocity place kicks. The kicks were filmed with a high-speed camera (400 Hz) and EMG recordings were obtained from 5 muscles of the kicking leg, including wire electrodes inserted into the m. iliopsoas. The EMG signals were compared to the kinetics of the kicking leg, which were calculated from the digitised film. The results showed hardly any torque reversal about the hip joint before impact. Angular deceleration of the thigh segment did not increase the angular velocity of the shank (work -3.57 to 0.0%). M. iliopsoas was active during the entire kicking motion (average EMG 65.1-100.9%), even in the period when the thigh was decelerating. Wire electrodes can successfully be applied to EMG recordings of fast unloaded movements.     

Infrapatellar fat pad pressure and volume changes of the anterior compartment during knee motion: possible clinical consequences to the anterior knee pain syndrome

This biomechanical study was performed to measure tissue pressure in the infrapatellar fat pad and the volume changes of the anterior knee compartment during knee flexion–extension motion. Knee motion from 120° of flexion to full extension was simulated on ten fresh frozen human knee specimens (six from males, four from females, average age 44 years) using a hydraulic kinematic simulator (30, 40, and 50 Nm extension moment). Infrapatellar tissue pressure was measured using a closed cell sensor. Infrapatellar volume change in the anterior knee compartment was evaluated subsequent to removal of the fat pad using a water-filled bladder. We found a significant increase of the infrapatellar tissue pressure during knee flexion, at flexion angles of <20° and >100°. The average tissue pressure ranged from 343 (±223) mbar at 0° to 60 (±64) mbar at 60° of flexion. The smallest volume in the anterior knee compartment was measured at full extension and 120° of flexion, whereas the maximum volume was observed at 50° of flexion. In conclusion, the data suggest a biomechanical function of the infrapatellar fat pad at flexion angles of <20° and >100°, which suggests a role of the infrapatellar fat pad in stabilizing the patella in the extremes of knee motion.     

An experimental in vivo method for analysis of local deformation on tibia, with simultaneous measures of ground reaction forces, lower extremity muscle activity and joint motion

This paper presents the pilot procedures of a new in vivo experimental method for measures of local bone deformation on tibia. The tibia transducer consists of a strain gauge mounted on a surgical staple, and was designed to measure local bone deformation. Pilot measurements were undertaken during two standardized conditions of forefoot and heel landing in seven healthy volunteers. Implantation of two tibia force transducers on tibia were preformed under local anaesthesia. The local peak tibia deformation occurred at 20–42 ms (median) after ground contact, and was up to eight times higher during stance phase loading compared with standing still on one leg. Ground reaction forces, muscle activation patterns and kinematics and were registered stimulataneously, and were used to validate that the observed local deformation on tibia occurred under controlled and clinically relevant conditions. The new method may be used for investigating local deformation within various bone structures of the lower extremity. There are further methodological issues to address before major clinical interpretations may be concluded. In order to verify that the strain gauge transducer system was valid, a controlled displacement of the staple shanks was performed with a micrometer, and showed a linear relationship between applied deformation and strain gauge response ( r = 0.97–0.99). In addition, a linear relationship was found between externally applied static forces and strain gauge response in a four-point bending cadaver system ( r = 0.96–0.98).     

Viscoelastic stress relaxation during static stretch in human skeletal muscle in the absence of EMG activity

The present study sought to investigate the role of EMG activity during passive static stretch. EMG and passive resistance were measured during static stretching of human skeletal muscle in eight neurologically intact control subjects and six spinal cord-injured (SCI) subjects with complete motor loss. Resistance to stretch offered by the hamstring muscles during passive knee extension was defined as passive torque (Nm). The knee was passively extended at 5^o/s to a predetermined final position, where it remained stationary for 90 s (static phase) while force and integrated EMG of the hamstring muscle were recorded. EMG was sampled for frequency domain analysis in a second stretch maneuver in five control and three SCI subjects. There was a decline in passive torque in the 90-s static phase for both control and SCI subjects, P<0.05. Although peak passive torque was greater in control subjects, P<0.05, there was no difference in time-dependent passive torque response between control (33%) and SCI (38%) subjects. Initial and final 5-s IEMG ranged from 1.8 to 3.4 μ V.s and did not change during a stretch or differ between control and SCI subjects. Frequency domain analysis yielded similar results in both groups, with an equal energy distribution in all harmonics, indicative of 'white noise'. The present data demonstrate that no measurable EMG activity was detected in either group during the static stretch maneuver. Therefore, the decline in resistance to static stretch was a viscoelastic stress relaxation response.     

The effects of 12 weeks of functional strength training on muscle strength,volume and activity upon exposure to elevated Gz forces in high-performance aircraft personnel

Background:Technological advancements in modern military and acrobatic jet planes have resulted in extraordinary psychophysiological loads being exerted upon flying personnel,including inducing neck and back pain.The purpose of this study was to examine the effects of 12 weeks of functional strength training on 1) the volume and strength of the neck and shoulder muscles and 2) muscular activity upon exposure to helmets of different masses and elevated Gz forces in a long-arm centrifuge in high-performance aircraft personnel.Methods:Eighteen participants underwent 12 weeks of functional strength training (n=12) or the control protocol(n=6) without additional strength training.Pre-and post-intervention tests included evaluations of isometric strength of the head extensor muscles,flexion,and lateral flexion and rotation,as well as magnetic resonance imaging (MRI)to measure the volume of the m.stemocleidomastoideus,m.trapezius,and deep neck muscles.Furthermore,during a long-arm centrifuge (+1.4 and +3Gz) protocol,the muscular activity levels of the m.sternocleidomastoideus,m.trapezius and m.erector spinae muscles were assessed without a flight helmet,with a helmet,and with a helmet and night vision goggles.Each participant's perception of muscular strain was noted immediately after the long-arm centrifuge protocol.Results:The maximal isometric strength in all exercises and muscle volumes increased in the training group but not the control group (P＜0.05).Relative muscle activity (％MVC) with a helmet decreased after the intervention in the training but not the control group (P=0.01).Relative muscle activity while wearing a helmet and night vision goggles was higher after intervention in the control group than in the training group (P＜0.01).The perceived muscular strain of the neck muscles induced by the long-arm centrifuge did not differ between the groups.Conclusions:Twelve weeks of functional strength training improves the maximal isometric strength and volume of neck and shoulder muscles and leads to lower relative muscle activation upon exposure to elevated Gz forces in a long-arm centrifuge.     

The role of inspiratory muscle training in the management of asthma and exercise-induced bronchoconstriction

Asthma is a pathological condition comprising of a variety of symptoms which affect the ability to function in daily life. Due to the high prevalence of asthma and associated healthcare costs, it is important to identify low-cost alternatives to traditional pharmacotherapy. One of these low cost alternatives is the use of inspiratory muscle training (IMT), which is a technique aimed at increasing the strength and endurance of the diaphragm and accessory muscles of respiration. IMT typically consists of taking voluntary inspirations against a resistive load across the entire range of vital capacity while at rest. In healthy individuals, the most notable benefits of IMT are an increase in diaphragm thickness and strength, a decrease in exertional dyspnea, and a decrease in the oxygen cost of breathing. Due to the presence of expiratory flow limitation in asthma and exercise-induced bronchoconstriction, dynamic lung hyperinflation is common. As a result of varying operational lung volumes, due in part to hyperinflation, the respiratory muscles may operate far from the optimal portion of the length-tension curve, and thus may be forced to operate against a low pulmonary compliance. Therefore, the ability of these muscles to generate tension is reduced, and for any given level of ventilation, the work of breathing is increased as compared to non-asthmatics. Evidence that IMT is an effective treatment for asthma is inconclusive, due to limited data and a wide variation in study methodologies. However, IMT has been shown to decrease dyspnea, increase inspiratory muscle strength, and improve exercise capacity in asthmatic individuals. In order to develop more concrete recommendations regarding IMT as an effective low-cost adjunct in addition to traditional asthma treatments, we recommend that a standard treatment protocol be developed and tested in a placebo-controlled clinical trial with a large representative sample.     

An efficient subset of morphological measures for articular cartilage in the healthy and diseased human knee

The relationship between three‐dimensional, MRI‐based morphologic measurements commonly taken of knee cartilage was examined to determine whether a subset of variables fully reflects differences observed in cartilage in cross‐sectional and longitudinal studies. The benefits of a subset of measures include increased statistical power due to reduced multiple comparisons, improved understanding of relationships between the morphologic measures of articular knee cartilage, and greater efficiency in reporting results. One hundred fifty‐two women (77 healthy and 75 with knee osteoarthritis) had coronal 3‐T MR images of the knee acquired at baseline and at 24 months. Measures of femorotibial cartilage morphology (surface area, thickness, volume, etc.) were determined in the medial and lateral tibia and femur. Cartilage thickness (mean cartilage thickness over the total area of the [subchondral] bone), total subchondral bone area, and percentage of denuded area of the subchondral bone were found to explain over 90% of the cross‐sectional and longitudinal variation observed in other measures of cartilage morphology commonly reported in knee osteoarthritis. Hence, these three measures of cartilage morphology explain nearly all variation in a larger set of common cartilage morphology measures both cross‐sectionally and longitudinally, both in healthy and in osteoarthritic knees. These variables hence define an efficient subset for describing structural status and change in osteoarthritic cartilage. Magn Reson Med 63:680–690, 2010. © 2010 Wiley‐Liss, Inc.     

Hip and knee muscle torque is not impaired in the first three months of a first-time lateral ankle sprain

ObjectivesThe primary objective was to compare hip and knee isometric muscle strength between individuals with a first-time acute lateral ankle sprain and controls. A secondary objective was to investigate hip and knee isometric muscle strength three months post-injury.DesignCross-sectional and prospective follow-up components.SettingLaboratory environment.ParticipantsForty-two participants (21 acute lateral ankle sprain and 21 controls) matched for age, sex, physical activity and leg dominance participated.Main outcome measuresHip and knee isometric muscle torque was assessed using a rigidly fixated hand-held dynamometer. Testing in acute lateral ankle sprain participants was performed within four weeks of injury and three months post-injury. Controls were tested at one timepoint.ResultsThere were no differences in hip or knee isometric muscle torque between acute lateral ankle sprain and control participants (mean differences <0.08). Hip and knee isometric muscle torque in acute ankle sprain participants did not differ between baseline and three months post-injury testing (mean difference <0.06).ConclusionsProximal lower limb isometric strength is not impaired within the first three months of sustaining a first-time lateral ankle sprain injury. This implies that hip and knee isometric strength deficits in individuals with CAI may occur at some later stage.     

The influence of hip rotations on muscle activity during unilateral weight-bearing exercises in individuals with and without genu varum: A cross-sectional study

ObjectivesHip rotation can influence gluteus medius (Gmed) muscle activity in individuals with genu varum (GV). This study examined different hip rotation positions on muscle activity during unilateral weight-bearing exercises in individuals with and without GV.DesignCross-sectional.SettingOutpatient physical therapy center.ParticipantsForty-six physically active males, divided between control (n = 23) and GV groups (n = 23).Main outcome measuresSurface electromyography measured Gmed and tensor fascia latae (TFL) activity during pelvic drop (PD) and wall press (WP) exercises with different hip rotations.ResultsIn the control group, WP with external rotation produced greater Gmed/TFL activity compared to other rotation positions. No difference was found for Gmed/TFL with PD in controls. In the GV group, Gmed activity increased with internal rotation in PD and WP; TFL activity increased only with external rotation in WP. Internal hip rotation produced higher Gmed/TFL activity than other positions in the GV group during both exercises. Greater Gmed/TFL activity was observed in the control group than GV during PD with external rotation, and WP with neutral positioning and external rotation.ConclusionsWP with external rotation in controls, and PD and WP with internal hip rotation in subjects with GV, are effective exercises to optimize GMed/TFL activity.