Context: Sport-related concussion (SRC) elevates risk for subsequent injury, which may relate to impaired perceptual-motor processes that are potentially modifiable. Objective: To assess a possible upper-extremity (UE) training effect on whole-body (WB) reactive agility performance among elite athletes with history of SRC (HxSRC) and without such history of SRC. Design: Cohort study. Setting: Residential training center. Participants: Elite athletes (12 males and 8 females), including 10 HxSRC and 10 without such history of SRC. Intervention: One-minute training sessions completed 2 to 3 times per week over a 3-week period involved verbal identification of center arrow direction for 10 incongruent and 10 congruent flanker test trials with simultaneous reaching responses to deactivate illuminated buttons. Main Outcome Measures: Pretraining and posttraining assessments of UE and WB reactive responses included flanker test conflict effect (incongruent minus congruent reaction time) and WB lateral average asymmetry derived from reaction time, speed, acceleration, and deceleration in opposite directions. Discrimination was assessed by receiver operating characteristic analysis, and training effect was assessed by repeated-measures analysis of variance. Results: Pretraining discrimination between HxSRC and without such history of SRC was greatest for conflict effect ≥80 milliseconds and WB lateral average asymmetry ≥18%. Each athlete completed 6 training sessions, which improved UE mean reaction time from 767 to 646 milliseconds (P < .001) and reduced mean conflict effect from 96 to 53 milliseconds (P = .039). A significant group × trial interaction was evident for WB lateral average asymmetry (P = .004), which was reduced from 24.3% to 12.5% among those with HxSRC. Conclusions: Suboptimal perceptual-motor performance may represent a subtle long-term effect of concussion that is modifiable through UE training, which appears to improve WB reactive capabilities.
Gary B. Wilkerson, Dustin C. Nabhan, and Ryan T. Crane
Javad Sarvestan, Alan R. Needle, Peyman Aghaie Ataabadi, Zuzana Kovačíková, Zdeneˇk Svoboda, and Ali Abbasi
Context: Chronic ankle instability is documented to be followed by a recurrence of giving away episodes due to impairments in mechanical support. The application of ankle Kinesiotaping (KT) as a therapeutic intervention has been increasingly raised among athletes and physiotherapists. Objectives: This study aimed to investigate the impacts of ankle KT on the lower-limb kinematics, kinetics, dynamic balance, and muscle activity of college athletes with chronic ankle instability. Design: A crossover study design. Participants: Twenty-eight college athletes with chronic ankle sprain (11 females and 17 males, 23.46 [2.65] y, 175.36 [11.49] cm, 70.12 [14.11] kg) participated in this study. Setting: The participants executed 3 single-leg drop landings under nontaped and ankle Kinesio-taped conditions. Ankle, knee, and hip kinematics, kinetics, and dynamic balance status and the lateral gastrocnemius, medial gastrocnemius, tibialis anterior, and peroneus longus muscle activity were recorded and analyzed. Results: The application of ankle KT decreased ankle joint range of motion (P = .039) and angular velocities (P = .044) in the sagittal plane, ground reaction force rate of loading (P = .019), and mediolateral time to stability (P = .035). The lateral gastrocnemius (0.002) and peroneus longus (0.046) activity amplitudes also experienced a significant decrease after initial ground contact when the participants’ ankles were taped, while the application of ankle KT resulted in an increase in the peroneus longus (0.014) activity amplitudes before initial ground contact. Conclusions: Ankle lateral supports provided by KT potentially decreases mechanical stresses applied to the lower limbs, aids in dynamic balance, and lowers calf muscle energy consumption; therefore, it could be offered as a suitable supportive means for acute usage in athletes with chronic ankle instability.
Kaitlin M. Gallagher, Anita N. Vasavada, Leah Fischer, and Ethan C. Douglas
A popular posture for using wireless technology is reclined sitting, with the trunk rotated posteriorly to the hips. This position decreases the head’s gravitational moment; however, the head angle relative to the trunk is similar to that of upright sitting when using a tablet in the lap. This study compared cervical extensor musculotendon length changes from neutral among 3 common sitting postures and maximum neck flexion while using a tablet. Twenty-one participants had radiographs taken in neutral, full-flexion, and upright, semireclined, and reclined postures with a tablet in their lap. A biomechanical model was used to calculate subject-specific normalized musculotendon lengths for 27 cervical musculotendon segments. The lower cervical spine was more flexed during reclined sitting, but the skull was more flexed during upright sitting. Normalized musculotendon length increased in the reclined compared with an upright sitting position for the C4-C6/7 (deep) and C2-C6/7 (superficial) multifidi, semispinalis cervicis (C2-C7), and splenius capitis (Skull-C7). The suboccipital (R 2 = .19–.71) and semispinalis capitis segment length changes were significantly correlated with the Skull-C1 angle (0.24–0.51). A semireclined reading position may be an ideal sitting posture to reduce the head’s gravitational moment arm without overstretching the assessed muscles.
Banu Unver, Kartal Selici, Eda Akbas, and Emin Ulas Erdem
The purpose of the study was to investigate the foot posture, ankle muscle strength, range of motion (ROM), and plantar sensation differences among normal weight, overweight, and obese individuals. One hundred and twenty-three individuals (42 normal weight, 40 overweight, and 41 obese) aged between 18 and 50 years participated in the study. Foot posture, ankle muscle strength, ROM, plantar sensation, and foot-related disabilities were evaluated. The relative muscle strength of left plantar flexors and invertors and light touch sensation of the left heel were significantly lower in obese individuals compared with overweight and normal weight (P < .016) individuals. Obese individuals had significantly reduced relative muscle strength of plantar flexors, dorsiflexor, and invertors, plantar flexion and inversion ROM in the left foot; and light touch sensation of the right heel compared with normal weight (P < .016) individuals. Foot Posture Index scores were significantly higher in obese individuals compared with overweight (P < .016) individuals. There were no significant differences in absolute muscle strength, vibration sensation, and foot-related disability scores among the 3 groups (P > .05). Obesity was found to have adverse effects on ankle muscle strength, ROM, and plantar light touch sensation. Vibration sensation was not affected by body mass index, and foot-related disability was not observed in obese adults.
Caleb D. Johnson and Irene S. Davis
Higher medial–lateral forces have been reported in individuals with stiffer foot arches. However, this was in a small sample of military personnel who ran with a rearfoot strike pattern. Therefore, our purpose was to investigate whether runners, both rearfoot and forefoot strikers, show different associations between medial–lateral forces and arch stiffness. A group of 118 runners (80 rearfoot strikers and 38 forefoot strikers) were recruited. Ground reaction force data were collected during running on an instrumented treadmill. Arch flexibility was assessed as the difference in arch height from sitting to standing positions, and participants were classified into stiff/flexible groups. Group comparisons were performed for the ratio of medial:vertical and lateral:vertical impulses. In rearfoot strikers, runners with stiff arches demonstrated significantly higher medial:vertical impulse ratios (P = .036). Forefoot strikers also demonstrated higher proportions of medial forces; however, the mean difference did not reach statistical significance (P = .084). No differences were detected in the proportion of lateral forces between arch flexibility groups. Consistent with previous findings in military personnel, our results indicate that recreational runners with stiffer arches have a higher proportion of medial forces. Therefore, increasing foot flexibility may increase the ability to attenuate medial forces.
Tyler N. Brown, AuraLea C. Fain, Kayla D. Seymore, and Nicholas J. Lobb
This study determined changes in lower limb joint stiffness when running with body-borne load, and whether they differ with stride or sex. Twenty males and 16 females had joint stiffness quantified when running (4.0 m/s) with body-borne load (20, 25, 30, and 35 kg) and 3 stride lengths (preferred or 15% longer and shorter). Lower limb joint stiffness, flexion range of motion (RoM), and peak flexion moment were submitted to a mixed-model analysis of variance. Knee and ankle stiffness increased 19% and 6% with load (P < .001, P = .049), but decreased 8% and 6% as stride lengthened (P = .004, P < .001). Decreased knee RoM (P < .001, 0.9°–2.7°) and increased knee (P = .007, up to 0.12 N.m/kg.m) and ankle (P = .013, up to 0.03 N.m/kg.m) flexion moment may stiffen joints with load. Greater knee (P < .001, 4.7°–5.4°) and ankle (P < .001, 2.6°–7.2°) flexion RoM may increase joint compliance with longer strides. Females exhibited 15% stiffer knee (P = .025) from larger reductions in knee RoM (4.3°–5.4°) with load than males (P < .004). Stiffer lower limb joints may elevate injury risk while running with load, especially for females.