Effect of soft and semi-rigid ankle braces on kinematic and kinetic changes of the knee and ankle joints after forward and lateral drop landing in healthy young women

2.1Participants

Ten healthy subjects including 15 women [age 21.8 ± 0.6 years (mean ± SD); height 156.5 ± 5.2 cm; body weight 47.9 ± 4.0 kg] voluntarily participated in this study. Subjects with history of a sprain of grade II or worse were excluded, current ligamentous defects, history of ligament or joint reconstruction or repair, dysfunction of the vestibular system affecting balance, or trauma (including fracture, myositis ossificans or burns). All the participants have never used any of the braces used in this study. The Ethics Committee of the Graduate School of Health Sciences, Hiroshima University approved the study protocol (ID number, C-254). The present study was designed 95 and implemented in accordance with the Declaration 96 of Helsinki.

Figure 1.

Soft brace (ZAMST FA-1; SIGMAX Devices, Inc., Japan).

Figure 2.

Semi-rigid brace (ZAMST FA-1; SIGMAX Devices, Inc., Japan).

2.2Intervention

Subjects were assigned to three randomly ordered experimental conditions (NB, SB, SRB). Zamst ankle braces (Nippon Sigmax Devices, Inc., Tokyo, Japan) were used in this study. The SB (Zamst FA-1) was a nylon supporter and was designed with two layers of support for weak and swollen ankles while allowing dorsiflexion-plantar flexion and inversion-eversion (Fig. 1). An inner wrap adjusts with a hook-and-loop closure to provide compression and control of the ankle and heel area. The SRB (Zamst A1) was a nylon supporter and included mediolateral reinforcement and two straps. It is designed to resist inversion loads while allowing dorsiflexion-plantar flexion and stabilize the ankle joint (Fig. 2). The mechanical property (i.e., angle-moment relationship) of the SB and SRB in the sagittal and coronal planes was quantified using a custom motorized mechanical testing device with an inline torque sensor (Transducer Tech Inc., USA) and optical encoder [16]. The ankle brace was donned on a wooden surrogate leg with mechanical ankle and subtalar joints. The mandrel extending from the surrogate leg was attached to a mounting jig which allowed precise positioning and the mechanical joint center was aligned with the center of motor output shaft. The servo motor was controlled by a motor drive in speed mode. Data acquisition (i.e. torque and joint displacement) and motor control was done using a custom LabVIEW program interfaced with a National Instrument PCI card (National Instrument Inc., TX, USA). The braces were fit to each subject by a single investigator in order to minimize within-subject and between-subject variations. The participants performed under three brace conditions (SRB, SB, and NB) in a random order on three separate days, with an intersession interval of at least 24 hours and no more than 48 hours between tests.

2.3Test protocol

To compare the effect of each condition, we measured kinematic and kinetic changes after forward and lateral drop landing under SB, SRB and NB conditions. The participants were instructed to perform the following actions: landing in the forward and lateral (90∘) direction from a 20-cm-height box, land at 50 cm to the left on the non-dominant limb only, stabilize as quickly as possible, place their hands on their hips once they were stabilized and remain still for 5 second while looking forward. Upper extremity movement was unrestricted during the jump but restricted after stabilization. They were allowed three practice trials for each condition to become familiar with the single-leg landing, with 1 min of rest after testing. The jump-landing task was performed on the non-dominant limb for unilateral assessment to assure consistency in data collection among the subjects [8]. The non-dominant limb of each subjects was defined by asking the preference when not kicking the ball. The measurement under each condition was conducted on different days to prevent fatigue and to avoid the subject becoming familiar with the task. The trial was discarded and repeated if the subject failed to jump or came into contact with the hurdle, fell upon landing, or the non-dominant limb came in contact with the dominant leg or landed outside of the force plate. All subjects were able to complete the task. Three successful trials were performed under each condition (SB, SRB, and NB). The average duration of each laboratory trial was 54.0 ± 5.0 minutes.

2.4Data collection

Kinematic data were recorded by 3-dimensional motion capture systems Vicon (Vicon motion systems, UK) with 16 cameras at a sampling rate of 100 Hz. A force plate (AMTI, USA) was used to measure the ground reaction force as kinetic data at a sampling rate of 1000 Hz. The instance of contacts on the force plate were defined as when the vertical ground reaction force was above 10 N [16]. Infrared reflective markers were applied to the subject according to the Plug-in Gait lower limb model. Marker data were post processed using Vicon Nexus 1.8.5 (Vicon Motion Systems, UK). Each subject had 16 reflective surface markers taped to specific anatomical landmarks on the pelvis, thigh, shank and shoe using hypoallergenic tape. Markers were placed on the right and left anterior superior iliac spine and posterior superior iliac spine, right and left lateral epicondyle of the knee, over the lower lateral 1/3 surface of the right and left thigh, right and left lateral malleolus along an imaginary line that passes through the transmalleolar axis, over the lower lateral 1/3 surface of the right and left shank (to determine the alignment of the ankle flexion axis), right and left over the second metatarsal head, and placed on the calcaneus at the same height above the plantar surface of the foot as the toe maker [21]. The global reference system of the laboratory was established so the anteroposterior axis was in the y-axis direction, the mediolateral axis was the x-axis, and the vertical axis was the z-axis.

Figure 3.

Angle-moment relationship of the SB and SRB in the sagittal and coronal plane.

The data of knee and ankle joints angle, ground reaction force (GRF), moment and GRF impulse (impulse) were filtered using a zero-lag, fourth-order, low-pass Butterworth filter with a cutoff frequency of 20 Hz. Angular displacements, force and moment of the knee and ankle joints were analyzed as each movement from initial contact to peak angle. Ankle and knee joint kinematic and kinetic data were averaged over three trials for each subject. Angle displacement (∘), moment (N⋅m) and pGRF (N/kg) were calculated from 100 ms before initial contact to 300 ms after contacts on ground. RFD (N/s) was calculated as the peak GRF divided by the time from initial contact to peak GRF [5]. Previous study [1] reported that RFD was defined as the change in force over the change in time. The normalized impulse (N/kg⋅s) , expressed the integrated GRF values between the time of initial contact to peak GRF. The average of the 3 trials in all parameters was calculated as the measurement value for each condition.

2.5Statistical analysis

A repeated-measures 1 (time) × 3 (NB, SB, SRB) ANOVA model was used for comparisons of knee flexion and valgus angle, ankle dorsiflexion and inversion angle, knee flexor moment (KFM), knee valgus moment (KVM), ankle plantar flexor moment (ADM) and inversion moment (AIM), peak vertical GRF (pGRF), time to peak GRF (TpGRF), RFD, and impulse for each condition. When appropriate, follow-up analyses were performed using post-hoc tests. An alpha level of 0.05 was the criterion for rejection of the null hypothesis for all statistical tests. Effect sizes were calculated using the Cohen d statistic. Statistical analysis was conducted using SPSS for Windows, version 23.0 (IBM Japan Co., Tokyo, Japan).

3.1Angle-moment relationship of SB and SRB

The angle-moment relationship of the SB and SRB in the sagittal and coronal planes is shown in Fig. 3. In both planes, SRB demonstrated more resistance than SB throughout the range.

3.2Kinematic and kinetic data

Knee flexion and valgus angle, ankle dorsiflexion and inversion angle in each brace condition and direction of drop landing are shown in Table 1. KFM, KVM, APM and AIM are shown in Table 2. pGRF, pGRF, RFD, and impulse are shown in Table 3.

The results indicate that knee flexion angle (P= 0.025) and RFD (P= 0.043) was significantly larger and TpGRF was shorter (P= 0.042) with the SRB than with the NB after forward drop landing. Moreover, the impulse of SRB after forward drop landing was significantly lower compared with SB and NB (P= 0.034). Knee flexion angle after lateral landing was significantly greater with the SB than with the NB (P= 0.009). Ankle dorsiflexion angle of SRB after lateral drop landing was significantly lower compared with SB (P= 0.011). Ankle plantar flexor moment after lateral drop landing was significantly higher with the SRB than with SB (P= 0.033) and NB (P= 0.014). In addition, TpGRF was significantly higher (P= 0.048) and RFD was significantly lower with the SRB than with the NB after lateral drop landing (P= 0.046).