Search Results

You are looking at 61 - 70 of 2,313 items for :

Clear All
Restricted access

Nelson Cortes, James Onate, João Abrantes, Linda Gagen, Elizabeth Dowling and Bonnie Van Lunen

The purpose of this study was to assess kinematic lower extremity motion patterns (hip flexion, knee flexion, knee valgus, and ankle dorsiflexion) during various foot-landing techniques (self-preferred, forefoot, and rear foot) between genders. 3-D kinematics were collected on 50 (25 male and 25 female) college-age recreational athletes selected from a sample of convenience. Separate repeated-measures ANOVAs were used to analyze each variable at three time instants (initial contact, peak vertical ground reaction force, and maximum knee flexion angle). There were no significant differences found between genders at the three instants for each variable. At initial contact, the forefoot technique (35.79° ± 11.78°) resulted in significantly (p = .001) less hip flexion than did the self-preferred (41.25° ± 12.89°) and rear foot (43.15° ± 11.77°) techniques. At peak vertical ground reaction force, the rear foot technique (26.77° ± 9.49°) presented significantly lower (p = .001) knee flexion angles as compared with forefoot (58.77° ± 20.00°) and self-preferred (54.21° ± 23.78°) techniques. A significant difference for knee valgus angles (p = .001) was also found between landing techniques at peak vertical ground reaction force. The self-preferred (4.12° ± 7.51°) and forefoot (4.97° ± 7.90°) techniques presented greater knee varus angles as compared with the rear foot technique (0.08° ± 6.52°). The rear foot technique created more ankle dorsiflexion and less knee flexion than did the other techniques. The lack of gender differences can mean that lower extremity injuries (e.g., ACL tears) may not be related solely to gender but may instead be associated with the landing technique used and, consequently, the way each individual absorbs jump-landing energy.

Restricted access

Elisabeth Macrum, David Robert Bell, Michelle Boling, Michael Lewek and Darin Padua

Context:

Limitations in gastrocnemius/soleus flexibility that restrict ankle dorsiflexion during dynamic tasks have been reported in individuals with patellofemoral pain (PFP) and are theorized to play a role in its development.

Objective:

To determine the effect of restricted ankle-dorsiflexion range of motion (ROM) on lower extremity kinematics and muscle activity (EMG) during a squat. The authors hypothesized that restricted ankle-dorsiflexion ROM would alter knee kinematics and lower extremity EMG during a squat.

Design:

Cross-sectional.

Participants:

30 healthy, recreationally active individuals without a history of lower extremity injury.

Interventions:

Each participant performed 7 trials of a double-leg squat under 2 conditions: a nowedge condition (NW) with the foot flat on the floor and a wedge condition (W) with a 12° forefoot angle to simulate reduced plantar-flexor flexibility.

Main Outcome Measures:

3-dimensional hip and knee kinematics, medial knee displacement (MKD), and ankle-dorsiflexion angle. EMG of vastus medialis oblique (VMO), vastus lateralis (VL), lateral gastrocnemius (LG), and soleus (SOL). One-way repeated-measures ANOVAs were performed to determine differences between the W and NW conditions.

Results:

Compared with the NW condition, the wedge produced decreased peak knee flexion (P < .001, effect size [ES] = 0.81) and knee-flexion excursion (P < .001, ES = 0.82) while producing increased peak ankle dorsiflexion (P = .006, ES = 0.31), ankle-dorsiflexion excursion (P < .001, ES = 0.31), peak knee-valgus angle (P = .02, ES = 0.21), and MKD (P < .001, ES = 2.92). During the W condition, VL (P = 0.002, ES = 0.33) and VMO (P = .049, ES = 0.20) activity decreased while soleus activity increased (P = .03, ES = 0.64) compared with the NW condition. No changes were seen in hip kinematics (P > .05).

Conclusions:

Altering ankle-dorsiflexion starting position during a double-leg squat resulted in increased knee valgus and MKD, as well as decreased quadriceps activation and increased soleus activation. These changes are similar to those seen in people with PFP.

Restricted access

Xingda Qu, Jianxin Jiang and Xinyao Hu

Knee injuries account for up to 60% of all sport injuries. 1 Half of the knee injuries are anterior cruciate ligament (ACL) injuries that are one of the most common and debilitating sport injuries. 2 – 5 In fact, ACL injuries are common in many sports activities, such as soccer, 2 basketball, 3

Restricted access

Ryan Zerega, Carolyn Killelea, Justin Losciale, Mallory Faherty and Timothy Sell

each year. 3 , 4 ACL reconstruction (ACLR) is the standard of care to reestablish knee joint stability following injury, but it frequently fails, either through reinjury or inability to successfully return to sport. 5 Secondary ACL injury (either ipsilateral surgical graft failure or contralateral

Restricted access

Ricky Anderson, Carol Courtney and Eli Carmeli

The purpose of this study was to see if vastus medialis oblique/vastus lateralis (VMO:VL) ratios could be increased by widening the squat stance and if the VMO activity increases with deeper ranges of knee flexion. Fifteen healthy subjects performed unloaded narrow and wide stance squats through three ranges of knee flexion: 30°, 60°, and 90°. The two squat stances were compared using a 2 × 3 ANOVA to see if the wide-stance squat had any significant difference in EMG activity for VMO: VL ratios compared to the narrow-stance squat. The difference in EMG activity of the VMO between the various angles for both squat stances was also compared. The ANOVA revealed no significant differences between the squat stances for VMO:VL ratios but did show the VMO:VL ratios to be significantly higher with increasing knee flexion angles. These findings suggest that the VMO is active throughout the 90° range and that increasing knee flexion angles can elicit greater activity of the VMO relative to the VL.

Restricted access

Dimitrios-Sokratis Komaris, Cheral Govind, Andrew Murphy, Alistair Ewen and Philip Riches

Movement alterations and neuromuscular adaptations in activities of daily living in patients with knee osteoarthritis are well documented. Studies have reported such changes in level walking, 1 – 3 stair ascent and descent, 4 , 5 and sit-to-stand. 6 – 12 The main reason suggested for the

Open access

Salman Nazary-Moghadam, Mahyar Salavati, Ali Esteki, Behnam Akhbari, Sohrab Keyhani and Afsaneh Zeinalzadeh

Anterior cruciate ligament deficiency (ACLD) is a common sports-related injury commonly followed by knee instability. 1 . Previous studies have shown that mechanical and functional instability of the knee, impaired muscle recruitment, loss of force, muscle atrophy, and impaired neuromuscular

Restricted access

Garry T. Allison, Renee Weston, Rachael Shaw, Jocelyn Longhurst, Linda James, Kathleen Kyle, Katrina Nehyba, Suy May Low and Michelle May

The purpose of this study was to assess the reliability of quadriceps muscle stiffness assessments in individuals with Osgood–Schlatter disease (OSD). Ten subjects were tested for four trials on two occasions within a 2-week period on a Kin-Com dynamometer. A regression coefficient was derived from force-angle data to determine stiffness. Intertriai and interday Intraclass correlations (ICC) and standard error of measurement (SEM) were derived from a repeated-measures ANOVA. Between-trial assessments were more reliable for the outer range 65 to 100° knee flexion (ICC = .95 & .81) than the inner range 35 to 65° knee flexion (ICC = .72 & .57) for both sessions. The average SEMs for outer and inner ranges (over 35°) were 1.1 and 1.3 N, respectively. Assessments between days were less reliable, which may reflect the weekly variation in the presentation of athletes' with- OSD. It remains unclear if the SEM lies within the limits of clinical significance.

Restricted access

Tania Suarez, Luca Laudani, Arrigo Giombini, Vincenzo Maria Saraceni, Pier Paolo Mariani, Fabio Pigozzi and Andrea Macaluso

Context:

Tearing of the anterior cruciate ligament (ACL) may disrupt the ability to recognize the knee position in space during limb-repositioning tasks, which is referred to as joint-position sense (JPS). Impairments in JPS have been shown to be lower during active than passive repositioning tasks, thus suggesting that coactivation patterns of the muscles surrounding the knee might compensate for the disrupted JPS and ensure accurate limb repositioning in ACL-deficient individuals.

Objective:

To investigate muscle coactivation patterns during JPS repositioning tasks in ACL-deficient and healthy individuals.

Design:

Prospective observational study.

Setting:

Functional assessment laboratory.

Participants:

8 men age 25 ± 8 y with isolated ACL rupture and 10 men age 30 ± 4 y with no history of knee injury.

Intervention:

JPS was evaluated by means of an electrogoniometer in a sitting position during either passive or active joint-positioning and -repositioning tasks with a 40° target knee angle.

Main Outcome Measures:

Root mean square (RMS) of the surface electromyogram from the vastus lateralis and biceps femoris muscles was measured during active joint positioning and repositioning.

Results:

Healthy participants showed a significant decrease in vastus lateralis RMS (−19%) and an increase in biceps femoris RMS (+26%) during joint repositioning compared with positioning. In contrast, ACL-deficient patients showed no modulation in muscle coactivation between joint positioning and repositioning, although they exhibited significantly lower RMS of the vastus lateralis (injured limb, −28%; uninjured limb, −21%) and higher RMS of the biceps femoris (injured limb, +19%; uninjured limb, +30%) than the healthy participants during joint positioning.

Conclusions:

The lack of modulation in muscle coactivation patterns between joint positioning and repositioning in ACL-deficient patients might be attributed to disrupted neural control after the injury-related loss of proprioceptive information. These results should be taken into account in the design of rehabilitation protocols with emphasis on muscle coactivation and JPS.

Restricted access

Guillaume Mornieux, Elmar Weltin, Monika Pauls, Franz Rott and Albert Gollhofer

Lateral movements with changes of direction are common in many team sports such as soccer or handball. During cutting maneuvers, the athlete performs a complex dynamic task by quickly changing their direction of movement while securing their balance. Knee joint control is an essential requirement