Sae Yong Lee and Jay Hertel
Altered foot dynamics due to malalignment of the foot may change plantar-pressure properties, resulting in various kinds of overuse injuries.
To assess the effect of foot characteristics on plantar-pressure-related measures such as maximum pressure, maximum pressure–time, and pressure–time integral underneath the medial aspect of the foot during running.
Laboratory. Participants: 8 men and 17 women.
Main Outcome Measures:
Static non-weight-bearing rear-foot and forefoot alignment and navicular drop were measured. Plantar-pressure data were collected while subjects jogged at 2.6 m/s on a treadmill. Maximum pressure, time to maximum pressure, and pressure–time integral of the medial side of the foot were extracted for data analysis. Multiple-regression analysis was used to examine the effect of arch height and rear-foot and forefoot alignment on maximum pressure and pressure–time integral in the medial side of the foot.
In the medial rear-foot and midfoot regions, only rear-foot alignment had a significant effect on the variance of maximum pressure and pressure–time integral. There were no significant difference effects in the medial forefoot region.
Rear-foot alignment was found to be a significant predictor of maximum plantar pressure and pressure–time integral in the medial rear-foot and midfoot regions. This indicates that control of rear-foot alignment may help decrease plantar pressure on the medial region of the foot, which may potentially prevent injuries associated with excessive rear-foot eversion.
Jennifer Erin Earl and Jay Hertel
To identify integrated EMG (I-EMG) activity of 6 lower-extremity muscles during the 8 Star Excursion Balance Tests (SEBTs).
Design and Setting:
Repeated measures, laboratory setting.
10 healthy young adults.
The SEBTs require the subject to balance on the stance leg and maximally reach with the contralateral foot along each of 8 lines extending from a common axis at 45° intervals.
I-EMG activity of the vastus medialis obliquus (VMO), vastus lateralis (VL), medial hamstring (MH), biceps femoris (BF), anterior tibialis (AT), and gas-trocnemius.
Significant differences were found in all muscles (P < .05) except the gastrocnemius (P = .08). VMO and VL activity tended to be greatest with anteriorly directed excursions, whereas the MH and BF activity were greatest with posteriorly directed excursions. AT activity was lowest with the lateral excursion.
Performance of the different SEBTs results in different lower-extremity muscle-activation patterns.
Nicole L. Cosby and Jay Hertel
A 20-y-old male Division 1 college basketball player sustained a grade 2 inversion ankle sprain during preseason that is preventing him from practicing and competing.
Clinical Outcomes Assessment:
The Foot and Ankle Ability Measure (FAAM) was administered to the injured athlete as an evaluative tool to provide the clinician with valuable subjective information on the patient’s self-reported function. The FAAM consists of 2 subscales: the activities of daily living (ADL) subscale and the sports subscale. Together the 2 subscales contain 29 questions (21 questions on the ADL and 8 on the sports subscale), which assess self-reported function and disability in the foot and ankle.
Clinical Decision Making:
The addition of the self-reported functional measures provides the clinician with more quantitative data to make clinical decisions than is possible with typical clinical exams. Self-reported functional assessments should not replace thorough clinical examination or sound clinical judgment; instead they should be an adjunct to them.
Clinical Bottom Line:
In addition to our objective assessment tools, the FAAM provides clinicians with a tool that can be used to assess function and disability through our patients’ self-reported responses. When used for evaluative purposes the FAAM can measure an individual’s changes in function and disability over time.
Lauren C. Olmsted and Jay Hertel
The effects of custom-molded foot orthotics on neuromuscular processes are not clearly understood.
To examine these effects on postural control in subjects with different foot types.
Between-groups, repeated-measures design.
Athletic training laboratory.
30 healthy subjects assigned to groups by foot type: planus (n = 11), rectus (n = 12), or cavus (n = 7).
Custom-fit semirigid orthotics.
Main Outcome Measures:
Static postural control was measured on a force plate. Dynamic postural control was measured using the Star Excursion Balance Test. Both measurements were assessed with and without orthotics at baseline and 2 weeks later.
For static postural control, a significant condition-by-group interaction was found. Subjects with cavus feet had a decreased center-of-pressure velocity while wearing orthotics. For dynamic postural control, a significant condition-by-direction-by-group interaction was found. Subjects with cavus feet had increased reach distances in 3 of 8 directions while wearing orthotics.
Custom orthotics were associated with some improvements in static and dynamic postural control in subjects with cavus feet.
John J. Fraser and Jay Hertel
Context: Intrinsic foot muscle (IFM) exercises are utilized clinically in the treatment of foot and ankle conditions. However, the effectiveness of training on IFM motor function is unknown. Objective: To study the effects of a 4-week IFM exercise program on motor function, perceived difficulty, and IFM motor activation measured using ultrasound imaging (USI) during 3 IFM exercises. Design: Single-blinded randomized control trial. Setting: Laboratory. Participants: A total of 24 healthy, recreationally active young adults without history of ankle–foot injury who have never performed IFM exercises participated (12 males and 12 females; mean age = 21.5 [4.8] y; body mass index = 23.5 [2.9] kg/m2) Intervention: Following randomization, participants allocated to the intervention group received a 4-week progressive home IFM exercise program performed daily. Participants in the control group did not receive any intervention. Main Outcome Measures: Clinician-assessed motor performance (4-point scale: 0 = does not initiate movement and 3 = performs exercise in standard pattern), participant-perceived difficulty (5-point Likert scale: 1 = very easy and 5 = very difficult), and USI motor activation measures
Luke Donovan, Joseph M. Hart and Jay Hertel
Ankle-destabilization devices are rehabilitation tools that may improve neuromuscular control by increasing lower-extremity muscle activation. Their effects should be tested in healthy individuals before being implemented in rehabilitation programs.
To compare EMG activation of lower-extremity muscles during walking while wearing 2 different ankle-destabilization devices.
15 healthy young adults (5 men, 10 women).
Surface EMG activity was recorded from the anterior tibialis, peroneus longus, lateral gastrocnemius, rectus femoris, biceps femoris, and gluteus medius as subjects walked on a treadmill shod, with an ankle-destabilization boot (ADB), and an ankle-destabilization sandal (ADS).
Main Outcome Measures:
Normalized amplitudes 100 ms before and 200 ms after initial heel contact, time of onset activation relative to initial contact, and percent of activation time across the stride cycle were calculated for each muscle in each condition.
The precontact amplitudes of the peroneus longus and lateral gastrocnemius and the postcontact amplitudes of the lateral gastrocnemius were significantly greater in the ADB and ADS conditions. In the ADB condition, the rectus femoris and biceps femoris postcontact amplitudes were significantly greater than shod. The peroneus longus and lateral gastrocnemius were activated significantly earlier, and the anterior tibialis, lateral gastrocnemius, and rectus femoris were activated significantly longer across the stride cycle in the ADB and the ADS conditions. In addition, the peroneus longus was activated significantly longer in the ADB condition when compared with shod.
Both ankle-destabilization devices caused an alteration in muscle activity during walking, which may be favorable to an injured patient. Therefore, implementing these devices in rehabilitation programs may be beneficial to improving neuromuscular control.
C. Collin Herb, Lisa Chinn and Jay Hertel
Lateral ankle sprain (LAS) is one of the most common injuries in active individuals. Chronic ankle instability (CAI) is a condition that commonly occurs after LAS and is associated with long-term disability and a high risk of multiple ankle sprains. Ankle taping is a commonly used intervention for the prevention of ankle sprains.
To analyze the ankle-joint coupling using vector coding during walking and jogging gait with the application of ankle tape and without ankle tape in young adults with and without CAI.
Observational laboratory study design. Patients walked and jogged on an instrumented treadmill while taped and not taped. Fifteen strides for each subject were collected and analyzed using a vector-coding technique to compare magnitude coupled motion, ratio of coupled motion, and the variability (VCV) within groups. Within-group means and 90% confidence intervals (CI) were compared between the taped and nontaped condition, and where the CIs did not overlap was considered significant.
A 12-camera 3D motion-capture system with instrumented treadmill.
12 patients with CAI and 11 healthy controls.
Main Outcome Measures:
Magnitude to coupled motion, ratio of coupled motion, and the VCV of shank–rear-foot joint coupling.
Magnitude of coupled motion and VCV were significantly lower in the taped condition than in the nontaped condition in both groups. Magnitude differences were identified near initial contact during walking and during swing phase of jogging. VCV differences were identified throughout the gait cycle at both walking and jogging. No differences were identified in theta between tape and nontaped conditions.
A decrease in the magnitude of coupled motion and VCV may represent a protective mechanism of ankle taping in CAI and healthy patients during gait.
Christopher Kuenze, Jay Hertel and Joseph M. Hart
Persistent quadriceps weakness due to arthrogenic muscle inhibition (AMI) has been reported after anterior cruciate ligament (ACL) reconstruction. Fatiguing exercise has been shown to alter lower extremity muscle function and gait mechanics, which may be related to injury risk. The effects of exercise on lower extremity function in the presence of AMI are not currently understood. The purpose of this study was to compare the effect of 30 min of exercise on quadriceps muscle function and soleus motoneuron-pool excitability in ACL-reconstructed participants and healthy controls.
Twenty-six (13 women, 13 men) healthy and 26 (13 women, 13 men) ACL-reconstructed recreationally active volunteers were recruited for a case-control laboratory study. All participants completed 30 min of continuous exercise including alternating cycles of inclined-treadmill walking and bouts of squats and step-ups. Knee-extension torque, quadriceps central activation ratio (CAR), soleus H:M ratio, and soleus V:M ratio were measured before and after 30 min of exercise.
There was a significant group × time interaction for knee-extension torque (P = .002), quadriceps CAR (P = .03), and soleus V:M ratio (P = .03). The effect of exercise was smaller for the ACL-R group than for matched controls for knee-extension torque (ACL-R: %Δ = −4.2 [−8.7, 0.3]; healthy: %Δ = −14.2 [−18.2, −10.2]), quadriceps CAR (ACL-R: %Δ = −5.1 [−8.0, −2.1]; healthy: %Δ = −10.0 [−13.3, −6.7]), and soleus V:M ratio (ACL-R: %Δ = 37.6 [2.1, 73.0]; healthy: %Δ = −24.9 [−38.6, −11.3]).
Declines in quadriceps and soleus volitional muscle function were of lower magnitude in ACL-R subjects than in healthy matched controls. This response suggests an adaptation experienced by patients with quadriceps AMI that may act to maintain lower extremity function during prolonged exercise.