Combined effect of gastrocnemius stretching with self-stabilising talus during subtalar supination on ankle kinematics in subjects with limited ankle dorsiflexion

Abstract

BACKGROUND:

Exercises that stretch the gastrocnemius (GCM) lead to greater ankle dorsiflexion (DF). GCM stretching combined with talar self-stabilisation has been reported to increase ankle DF range of motion (ROM). However, excessive subtalar and midtarsal pronation during GCM stretching may compensate for reduced ankle DF. Thus, this study examined the combined immediate effect of stretching GCM and stabilising talus and subtalar supination on limited ankle DF.

OBJECTIVE:

This study aimed to investigate the immediate effect of GCM stretching alone, GCM stretching with talar self-stabilisation and GCM stretching with talar self-stabilisation and subtalar supination on ankle kinematics in subjects with limited ankle DF.

METHODS:

Fifteen subjects with limited ankle DF were recruited. The subjects performed the three abovementioned methods.

RESULTS:

GCM stretching with talar self-stabilisation and subtalar supination significantly increased open-chain and closed-ankle DF ROM compared with GCM stretching alone. Moreover, GCM stretching combined with talar self-stabilisation and subtalar supination significantly increased open-chain ankle DF ROM with knee straight compared with pre-intervention ( $P<$ 0.017).

CONCLUSIONS:

The preferred method to increase ankle DF ROM is GCM stretching combined with talar self-stabilisation and subtalar supination.

Keywords

Ankle dorsiflexion stretch subtalar joint

1. Introduction

Limited ankle dorsiflexion (DF) is associated with overuse and multiple chronic injuries of the lower extremities, including iliotibial band friction synd- rome [1], patellofemoral pain syndrome [2], Achilles tendinopathy [3, 4], plantar fasciitis [5] and calf muscle tightness [6]. These conditions are usually attributed to irregular tibial advancement over the foot during the mid-stance phase and an early heel-off strategy that brings the body over the foot during the stance phase of the gait cycle [7, 8, 9]. During closed-chain movements such as gait, the talus slides forward and medial during subtalar eversion and pronation. The tibia will move relatively more than the talus and anteriorly glide over the talus as the tibia moves over the foot and the ankle dorsiflexes and pronates. In addition, conjunct external rotation is required to achieve the end range of DF. Several factors may cause limited ankle DF, such as tight calf muscles, loss of mobility in the soft tissue or capsular ligament or a reduction in the flexibility of the talocrural, subtalar or midtarsal joints [10]. In particular, inadequate accessory motion or reduced posterior glide of the talocrural joint is likely influenced by an arthrokinematic restriction of the subtalar joint.

Many previous studies have investigated methods for improving the open- and closed-chain movements in ankle DF range of motion (ROM), including stretching of the gastrocnemius (GCM), talocrural joint mobilisation and GCM stretching combined with talocrural joint mobilisation [11, 12, 13, 14]. Of these methods, stretching of the GCM leads to greater open-chain ankle DF ROM owing to changes in pain onset and increased tolerance of the stretch [14]. The combination of GCM stretching and talocrural joint mobilisation increased the open-chain ankle DF ROM (posterior talar glide) significantly more than GCM stretching alone in subjects with limited ankle DF [12]. Previous studies have demonstrated that anterior-to-posterior talar mobilisation increased open-chain ankle DF active ROM because of the mechanical correction of the bony positioning fault in patients with chronic ankle instability [13]. In addition, studies have used talocrural joint mobilisation to fix the talus at the limit of the posterior talar glide, applying pressure to stabilise the ankle and facilitating relative tibial advancement over the fixed foot during closed-chain activities [12, 15]. However, in this study, we modified talocrural joint mobilisation using Kinesio taping, instead of sustaining the mobilisation by hand, to allow the talus to self-stabilise. In addition, excessive subtalar and midtarsal pronation during weight-bearing activities may compensate for reduced ankle DF [7, 16, 17, 18, 19]. To prevent excessive compensatory pronation in individuals with limited ankle DF, subtalar joint supination may be included in interventions to increase both open- and closed-chain ankle DF ROM. However, no study has examined the effect of subtalar joint supination or the combined use of the three methods (GCM stretching alone, talar stabilisation and subtalar joint supination) on limited ankle DF.

Furthermore, various methods have been used to assess ankle DF as an outcome measure of the effectiveness of therapeutic interventions such as open- (non-weight-bearing) and closed-chain (weight- bearing) conditions [10, 20, 21]. Open-chain measurements typically attempt to better isolate talocrural joint motion by preventing subtalar joint motion [22]. Compared with these, closed-chain measurements have several advantages such that it is relatively easy to perform and involves a more functional position in that greater force from the body weight itself is applied to the ankle joint, thereby stressing the joint through its full excursion [23]. Therefore, this study included open-chain ankle DF ROM with the knee straight and bent and closed-chain ankle DF ROM with the knee straight.

In this study, we aimed to prevent unwanted excessive subtalar joint motion such as eversion or pronation during GCM stretching by allowing the talus to self-stabilise through subtalar supination. Thus, we conducted a navicular drop (ND) test, which is a simple clinical method for assessing foot eversion and pronation [24].

This study aimed to investigate the immediate effect of GCM stretching alone, GCM stretching with talar self-stabilisation and GCM stretching combined with talar self-stabilisation and subtalar supination on ankle kinematics (open-chain ankle DF ROM with the knee straight, open-chain ankle DF ROM with the knee bent, closed-chain ankle DF ROM with the knee straight and ND) in subjects with limited ankle DF. We hypothesised that the three ankle DF ROMs and ND would differ between the three methods in subjects with limited ankle DF.

Table 1
Subjects’ demographic information (mean $\pm$ SD)

Parameters	Mean $\pm$ SD		CI (95%)
Age (years)	20.93	$\pm$ 2.15	19.74, 22.13
Height (cm)	166.67	$\pm$ 6.22	163.22, 170.11
Weight (kg)	69.58	$\pm$ 12.84	62.47, 76.70
Body mass index (kg/m ${}^{2}$ )	24.95	$\pm$ 3.58	22.96, 26.93
Open chain ankle DF ROM with knee straight ${}^{\text{a}}$ ( ${}^{\circ}$ )	$-$ 27.80	$\pm$ 5.60	$-$ 24.70, $-$ 30.90
Open chain ankle DF ROM with knee bent ( ${}^{\circ}$ )	8.60	$\pm$ 3.89	6.45, 10.75
Closed chain ankle DF ROM with knee straight ( ${}^{\circ}$ )	22.63	$\pm$ 4.91	19.91, 25.35
Navicular drop (mm)	5.20	$\pm$ 3.75	3.13, 7.27

Abbreviations: CI, confidence interval; DF, dorsiflexion; ROM, range of motion. ${}^{\text{a}}$ Positive angles indicates dorsiflexion, negative angles indicates plantar flexion.

2. Methods

2.1 Subjects

In total, 15 subjects with limited ankle DF participated in this study, including five from the pilot study (Table 1). Subjects with $<$ 10 ${}^{\circ}$ of ankle DF passive ROM with the knee straight in the prone position were considered eligible to participate in this study [25, 26]. ROM of both ankles was measured under limited DF in all subjects. Data were collected from the ankle with the smaller DF ROM. We decided that an ankle had poor DF ROM when a bilateral comparison indicated a difference in DF ROM of $<$ 1 ${}^{\circ}$ . Thus, 10 subjects had bilateral and five had asymmetrical unilateral limitations of ankle DF. All subjects were physically active, which was defined as exercising at least 20 min per day for 3 days or more per week [27]. Subjects with histories of surgery in the lower extremities, fractures, neurological diseases, hip and knee flexion contractures or musculoskeletal soft tissue injury of the lower extremity such as ankle sprain within 6 months before the study were excluded. Prior to participation, the subjects provided written informed consent. The investigation was approved by the Local University Institutional Review Board.

2.2 Procedure

Prior to the interventions, ankle DF ROM was measured three times to determine the demographic information of subjects in previous studies and those in the present study. First, limited ankle DF was determined by measuring the open-chain ankle DF maximum ROM with the knee straight in the prone position using a 14-inch stainless steel goniometer. Second, open-chain ankle DF maximum ROM with the knee bent in the sitting position and closed-chain ankle DF maximum ROM with the knee straight in the standing position was measured using digital inclinometer (Gain Express Holdings Ltd., Shenzhen, China). All measurements were performed twice; the goniometer and inclinometer were removed between the first and second measurements. The mean of two maximum values was used for data analysis.

For the three stretching exercises, the subjects were instructed by the principal investigator (PI) on the correct posture and performance of the stretching exercises. For warm-up, the subjects were allowed to practice the exercises for approximately 10 min. They were allowed to perform stretching in less than three repetitions. A 5-min rest period was allowed after the familiarisation period and before data collection. All subjects randomly performed all the three methods (GCM stretching alone, GCM stretching with talar self-stabilisation and GCM stretching with talar self-stabilisation and subtalar supination) to avoid bias caused by learning or fatigue. At the start of the intervention, the subjects pulled out numbers written on a paper from a small box to determine the order in which they were to perform the tasks (GCM stretching alone in 4, GCM stretching with talar self-stabilisation in 5 and GCM stretching with talar self-stabilisation and subtalar supination in 6). Each stretch was held for 30 s and performed five times. The subjects were allowed a 10-s rest period between stretches [28]. Based on previous studies, the subjects had a washout period of 15 min between the methods to avoid bias due to the effects of stretching (5 repetitions $\times$ 3 min $=$ 15 min total rest) [29]. If heel contact was not maintained, the data collected were discarded and the test was performed again. The PI removed the tape before measuring the dependent variables. Then, open-chain ankle DF ROM with the knee straight and bent, closed-chain ankle DF ROM with the knee straight and ND were measured immediately after each stretching exercise.

2.3 Measurement of dependent variables

2.3.1 Open-chain ankle DF ROM with the knee straight

Open-chain ankle DF ROM with the knee straight was measured using the goniometer. The subjects were put in the prone position, with feet extending beyond the end of the treatment table. The PI maintained a neutral subtalar joint position and applied force to the plantar surface of the forefoot and midfoot until further movement was firmly resisted. A second investigator confirmed the neutral position of the subtalar joint. The PI marked the three points on the lateral malleolus, fibular head and fifth metatarsal bone using a pen. The three marks were kept the same until the end of the study [30]. The fulcrum of the goniometer was placed over the lateral malleolus, and the stationary and moving arms were aligned with the fibular head and parallel to the fifth metatarsal bone, respectively. A previous study had reported good intrarater (0.96–0.97) and interrater reliability (0.91–0.92), with standard errors of measurement (SEM) of 0.70 ${}^{\circ}$ –0.85 ${}^{\circ}$ and 1.04 ${}^{\circ}$ –1.13 ${}^{\circ}$ , respectively, for open-chain ankle DF ROM with the knee straight measured with a goniometer [20].

2.3.2 Open-chain ankle DF ROM with the knee bent

The talar swing test was performed to assess talocrural joint posterior glide and conjunct external rotation of the talus during passive ankle DF. However, we did not use this method to directly measure talar swing, posterior talar glide and the conjunct external rotation of the talus. Thus, for interpretation accuracy, we used “open-chain ankle DF ROM with the knee bent” instead of “talar swing test” to describe the test performed in this study. The subjects were instructed to sit, with their thighs completely supported on the edge of the treatment table. The test foot was aligned with the subtalar joint in a neutral position parallel to the floor. The second investigator visually monitored the starting and end positions of the measurement. The PI’s thumbs were positioned on the dome of the anterior talus to push the talus posteriorly while the foot was kept parallel to the floor with the subtalar joint in a neutral position until further movement was firmly resisted [10, 21, 31]. The second investigator placed an inclinometer just distal to the tibial tuberosity and recorded the angle of knee flexion when the tibia had stopped moving. After one measurement of open-chain ankle DF ROM with the knee bent, the subjects stood in a comfortable position and then returned to the sitting position for the next trial. Good intrarater reliability (0.99) was reported for the talar swing test in a previous study [31].

2.3.3 Closed-chain ankle DF ROM with the knee straight

The subjects were instructed to stand and step forward with the non-test leg while keeping the test foot in line with the long axis of the leg, knee in extension and heel on the ground. The subject leaned forward and flexed the hip and knee of the non-test leg, as needed, to allow for maximal ankle DF of the test. The PI marked three points on the fibular head, lateral malleolus and half point using a pen. The inclinometer was positioned on the half point in line with the fibular head and lateral malleolus. The maximal position was the point at which the heel began to lift from the floor. The second investigator visually monitored this motion to lift the heel from the floor. The DF ROM was recorded, and the subject returned to the starting position for the next trial. Intrarater reliability values ranged from 0.88 to 0.89, with a SEM of 2.2 ${}^{\circ}$ –2.3 ${}^{\circ}$ and minimal detectable changes of 6.1 ${}^{\circ}$ –6.4 ${}^{\circ}$ . The interrater reliability was 0.82, with a SEM of 2.82 ${}^{\circ}$ [32].

2.3.4 ND test

ND was assessed while the subjects were in the sitting position. The PI marked each subject’s navicular tuberosity in the subtalar neutral position using a pen. Then, the investigator measured the difference between the vertical position of the navicular tuberosity (distance between the navicular tubercle and floor) when the subject was in the sitting position and that when the subject was in the standing position, in millimetres using a ruler (i.e. a modified Brody approach) [33, 34, 35]. A previous study reported using the average measurement to define neutral foot (ND, 5–9 mm), pronated foot (ND, $>$ 10 mm) or supinated foot (ND, $<$ 4 mm). The intrarater reliability was 0.96 [35].

Figure 1.

Gastrocnemius stretching alone.

2.4 Three types of GCM stretching (independent variables)

2.4.1 GCM stretching alone

The subjects were instructed to stand on two scales to ensure that they leaned forward by the same amount each time. The subject placed the test foot over the line that bisected the heel and the second toe on the scale to maintain the neutral foot position. The weight on the test leg (side with limited ankle DF ROM) with the knee extended was maintained at 60% $\pm$ 5% of the subject’s body weight using the scales to measure the force applied to the test leg during the stretch [36]. The test leg was placed one-step length behind the contralateral leg. The subjects were asked to flex their hips forward until they felt maximal tolerable stretch of GCM in the test leg [37]. The subjects placed their hands on the wall for balance and maintained a straight knee without heel off in the test leg during the stretch (Fig. 1).

Figure 2.

Gastrocnemius stretching with self-stabilising talus.

2.4.2 GCM stretch with self-stabilising talus

The PI applied a 20-cm long Kinesio tape to stabilise the talus during DF. The single layer of the tape was fully stretched and directly applied to the skin, with the subjects in the sitting position. The tape was applied starting from the anterior aspect of the talus and extended to the lateral malleolus, calcaneus and back to the anterior aspect of the talus [38]. The tape went once around the ankle. The second investigator tactilely confirmed the tape attachment and visually monitored the tape removal during the stretch. After the tape was applied, the subjects performed the GCM stretching in the same way as before, but including talar self-stabilisation this time (Fig. 2).

2.4.3 GCM stretching with talar self-stabilisation and subtalar supination

The PI applied the Kinesio tape for talar self-stabilisation. Then, another 20-cm-long Kinesio tape was fully stretched and directly applied on the skin. The tape was applied starting from the fibula and extended to the lateral malleolus, calcaneus and middle third of the medial tibia [39]. The tape went once around the ankle. The second investigator tactilely confirmed the tape attachment and visually monitored the tape removal and heel contact during the stretch. After the tape was applied, the subjects performed the GCM stretching in the same way as with talar self-stabilisation, but including subtalar supination this time (Fig. 3).

Figure 3.

Gastrocnemius stretching with talar self-stabilisation and subtalar supination.

Table 2

Descriptive statistics by methods (mean $\pm$ SD)

Variable	GCM stretching alone		GCM stretch with self-stabilising talus		GCM stretching with talar self-stabilisation and subtalar supination
	Three methods
Open chain ankle DF ROM with knee straight ${}^{\text{a}}$ ( ${}^{\circ}$ )	$-$ 21.87	$\pm$ 6.31 ${}^{\text{b},\text{c}}$	$-$ 19.13	$\pm$ 3.89	$-$ 17.80	$\pm$ 4.78
Open chain ankle DF ROM with knee bent ( ${}^{\circ}$ )	13.80	$\pm$ 4.68 ${}^{\text{c}}$	14.37	$\pm$ 4.84	15.60	$\pm$ 5.09
Closed chain ankle DF ROM with knee straight ( ${}^{\circ}$ )	23.33	$\pm$ 6.41 ${}^{\text{b},\text{c}}$	25.47	$\pm$ 6.84	27.01	$\pm$ 6.48
Navicular drop (mm)	4.33	$\pm$ 3.33	4.46	$\pm$ 3.50	4.40	$\pm$ 2.77

Abbreviations: GCM, gastrocnemius; DF, dorsiflexion; ROM, range of motion. ${}^{\text{a}}$ Positive angles indicates dorsiflexion, negative angles indicates plantarflexion. ${}^{\text{b}}$ Indicates significant difference from GCM stretch with self-stabilising talus ( $P<$ 0.017). ${}^{\text{c}}$ Indicates significant difference from GCM stretching with talar self-stabilisation and subtalar supination ( $P<$ 0.017).

2.5 Statistical analyses

The G*Power ver. 3.1.6 software package (Franz Faul, Kiel University, Kiel, Germany) was used to calculate the sample size and conduct post power analyses. Using data obtained from a pilot study of five subjects, we calculated the necessary sample size to achieve a power of 0.80 and an effect size (ES) of 0.85 and found that four subjects are needed (calculated from the partial $\eta^{2}$ of 0.42 from the pilot study), with an $\alpha$ level of 0.05. The PASW Statistics 18 software (SPSS, Chicago, IL, USA) was used to perform all statistical analyses. Data on three ankle DF ROM and ND before and after GCM stretching alone, GCM stretching with talar self-stabilisation and GCM stretching with talar self-stabilisation and subtalar supination were summarised using means, standard deviation (SD) and 95% confidence interval. The total ankle DF ROM and ND data were normally distributed according to a one-sample Kolmogorov-Smirnov test; hence, we used parametric statistics. A 2 $\times$ 3 analysis of variance (ANOVA) was used to assess the statistical significant differences in time (pre-intervention and post-intervention) and the three methods. If a significant time-by-method interaction was not found, the main effects of time and method were determined. If a significant time-by-method interaction was revealed, Bonferroni’s correction was used to determine the simple effect (with $\alpha=$ 0.05/3 $=$ 0.017). ES was calculated to determine meaningful changes between methods (differences in the mean between interventions/SD of pre-intervention) [40]. An ES of $\leqslant$ 0.20 represents a small change; 0.50, a moderate change; and 0.80, a large change [41].

3. Results

The Kolmogorov-Smirnov tests showed no significant differences in the total ankle DF ROM and ND data among the three methods (open-chain ankle DF ROM with knee straight: $P=$ 0.890, $Z=$ 0.58; open-chain ankle DF ROM with knee bent: $P=$ 0.965, $Z=$ 0.50; closed-chain ankle DF ROM with knee straight: $P=$ 0.802, $Z=$ 0.64; ND: $P=$ 0.869, $Z=$ 0.60).

The two-way ANOVA revealed significant time-by-method interactions for open-chain ankle DF ROM with the knee straight ( $F_{2,13}=$ 5.272, $P=$ 0.0008). GCM stretching with talar self-stabilisation and subtalar supination resulted in a significantly greater open-chain ankle DF ROM with the knee straight than pre-intervention (mean difference, 5.20 ${}^{\circ}$ $\pm$ 1.88 ${}^{\circ}$ ; $P=$ 0.015; ES, 0.77) and GCM stretching alone (mean difference, 4.07 ${}^{\circ}$ $\pm$ 7.92 ${}^{\circ}$ ; $P=$ 0.010; ES, 0.60) (Table 2).

There were no significant time-by-method interactions for open-chain ankle DF ROM with the knee bent ( $F_{2,13}=$ 3.479, $P=$ 0.380). The main effect of time on open-chain ankle DF ROM with the knee bent was that there was no significant difference between pre- and post-intervention ( $F_{2,13}=$ 1.511, $P=$ 0.229). The main effect of method on open-chain ankle DF ROM with the knee bent was that there was significant difference among the three methods ( $F_{2,13}=$ 3.479, $P=$ 0.038). Post-hoc pairwise comparisons revealed that GCM stretching with talar self-stabilisation and subtalar supination resulted in significantly greater open-chain ankle DF ROM with the knee bent than GCM stretching alone (mean difference, 1.80 ${}^{\circ}$ $\pm$ 8.33 ${}^{\circ}$ ; $P=$ 0.004; ES, 0.46; Table 2).

There were significant time-by-method interactions for closed-chain ankle DF ROM with the knee straight ( $F_{2,13}=$ 6.423, $P=$ 0.003). GCM stretching with talar self-stabilisation and subtalar supination resulted in significantly greater closed-chain ankle DF ROM with the knee straight than GCM stretching alone (mean difference, 3.68 ${}^{\circ}$ $\pm$ 12.64 ${}^{\circ}$ ; $P=$ 0.001; ES, 0.98) (Table 2).

There were no significant time-by-method interactions for ND ( $F_{2,13}=$ 0.028, $P=$ 0.972). No significant effect of time and method on ND was found ( $F_{2,27}=$ 0.003, $P=$ 0.943, $F_{2,27}=$ 0.031, $P=$ 0.970; Table 2).

4. Discussion

This study investigated the immediate effect of GCM stretching alone, GCM stretching with talar self-stabilisation and GCM stretching with talar self-stabilisation and subtalar supination on ankle DF and ND in subjects with limited ankle DF. Compared with GCM stretching alone, GCM stretching together with talar self-stabilisation and subtalar supination significantly increased open-chain and closed-chain ankle DF ROM. Moreover, compared with pre-intervention, GCM stretching with talar self-stabilisation and subtalar supination significantly increased the open-chain ankle DF ROM with knee straight.

Our results revealed significantly greater ankle DF ROM with the knee straight in GCM stretching combined with talar self-stabilisation and subtalar supination than in GCM stretching alone, increasing by 4.07 ${}^{\circ}$ (18.61%) in the open-chain ankle and by 3.68 ${}^{\circ}$ (15.77%) in the close-chain ankle. A previous study has reported a change in open-chain ankle ROM with the knee straight of 0.70 ${}^{\circ}$ –0.85 ${}^{\circ}$ in the control and experimental groups, which was greater than SEM [20]. Another study reported that SEM of closed-chain ankle DF ROM with the knee bent that was measured with an inclinometer was 1.3 ${}^{\circ}$ –1.4 ${}^{\circ}$ [42]. Changes greater than SEM indicate true differences from SEM. Thus, these changes are not due to measurement error but are caused by the effect of GCM stretching combined with talar self-stabilisation and subtalar supination. A previous study has reported that the change in the open-chain ankle DF ROM with the knee straight measured using an inclinometer on the uninjured and lateral ankle sprain sides was 0.58 ${}^{\circ}$ –0.86 ${}^{\circ}$ greater than SEM [10]. These findings also support the present study hypothesis. However, to the best of our knowledge, this is the first study to report superior results for the GCM stretching combined with talar self-stabilisation during subtalar supination compared with GCM stretching alone in subjects with limited ankle DF. Thus, these results cannot be compared with the results of other studies. GCM stretching with talar self-stabilising talus and subtalar supination could maintain a normal ankle joint alignment during GCM stretching by keeping the foot rigid. Stabilisation of the talus by taping both at the talocrural and subtalar joints may restrict excessive foot pronation in subjects with limited ankle DF, leading to increased ankle DF. Taping around the talocrural and subtalar joints possibly influences proprioceptive function and awareness of the foot position during the GCM stretch. A previous study has demonstrated that taping the ankles of subjects who did not have ankle injuries improved proprioception after exercise [43]. Therefore, our results indicated that GCM stretching with talar self-stabilisation and GCM stretching with talar self-stabilisation and subtalar supination may be more effective in improving limited ankle DF than GCM stretching alone.

We found that the open-chain ankle DF ROM with the knee bent was significantly greater in GCM stretching with talar self-stabilisation and subtalar supination, increasing by 1.8 ${}^{\circ}$ (13.04%), than in GCM stretching alone. This finding also supported the original research hypothesis. Restricting excessive subtalar pronation might facilitate DF at the talocrural joint because DF can occur at the subtalar and midtarsal joints as well as at the talocrural joint, when the subtalar joint is pronated during weight-bearing activities [44]. However, no significant difference in open-chain ankle DF ROM with the knee bent was found between GCM stretching alone and GCM stretching with talar self-stabilisation, although the latter was associated with an increase of 0.57 ${}^{\circ}$ (4.13%). A previous study has reported that subjects with limited ankle DF who underwent sustained talocrural joint self-mobilisation during GCM stretching showed significantly greater open-chain ankle DF ROM with the knee bent than those who performed GCM stretching alone [12]. The disagreement between the results of present and previous studies may be due to the difference in exercise methods used. Previous studies stabilised the talus manually during GCM stretching, but the present study used Kinesio taping for self-mobilisation [12, 45]. Self-mobilisation with a strap, tape or towel is commonly used in clinical settings to increase ROM without pain [15, 30, 46, 47]. Thus, we designed a talar self-stabilisation technique to increase ankle DF during GCM stretching. However, our method simply stabilises the talus (tibia anterior glide in the closed kinematic chain) but does not move it directly. Thus, our results and those of previous studies suggested that GCM stretching with talar self-stabilisation by taping the joint is insufficient to increase open-chain ankle DF ROM with the knee bent. In addition, a previous study has reported that the change in open-chain ankle DF ROM with the knee bent that was measured with an inclinometer on the uninjured side was 0.34 ${}^{\circ}$ , which was greater than SEM, but that measured on the lateral ankle sprain side was 2.00 ${}^{\circ}$ , which was less than SEM [10]. Therefore, this study recommends the use of GCM stretching combined with talar self-stabilisation and subtalar supination to increase the open-chain ankle DF ROM with the knee bent in subjects with limited ankle DF, but with caution.

No significant differences in ND were observed among the three methods. This finding does not support the original research hypothesis. The hypothesis was based on the theory that reduced ankle DF may be compensated for by subtalar and midtarsal pronation during weight-bearing activities [7, 16, 17, 18, 19]. Accordingly, GCM stretching may lead to a pronated foot in subjects with limited ankle DF. Although the present study did not reveal a decrease in ND, different results may have been observed if ND had been measured while GCM stretching was being performed. We measured ND immediately after the stretches. Thus, over the long term, GCM stretching alone might contribute to a change in foot position. In addition, the study subjects were in the neutral foot group (mean ND before intervention, 0.52) according to the definition of previous researcher [35] (neutral foot: ND, 5–9 mm). The results would change if the subjects had pronated feet. Finally, we used the Kinesio tape to prevent subtalar pronation during GCM stretching. The most popular taping methods are the McConnell and Kinesio taping techniques [48]. In general, McConnell taping has been used to correct joint alignment because a rigid tape exerted no tension on the skin of the patient where it is applied. However, this study used the Kinesio tape because its favourable adhesive properties facilitate easy use and prevent allergic reactions and stretch tolerance can be sufficiently altered via sensory mechanisms; hence, the clinical use of Kinesio taping is widespread [49]. The results with Kinesio taping could imitate those obtained with McConnell taping. However, a previous study has reported that Kinesio taping reduces patellofemoral pain syndrome-associated pain but does not change patellar alignment. Previous researchers believed that Kinesio taping can be applied at 50%–85% tension on the skin to restrict partial or full joint motion, but this taping tension was insufficient to correct patellar alignment [50]. Thus, this study applied 120%–130% maximal tension (full-stretch tape) on the ankle joint. In addition, previous results have indicated that McConnell taping corrects patellar alignment and tracking [51] but does not improve the motor function and proprioception of patients with patellofemoral pain syndrome [52, 53]. In addition, conjunct external rotation of the talus occurs near the end range of DF [10].

The goal of this study was to prevent excessive pronation and anterior glide of the talus on the calcaneus by using the Kinesio tape. Complete blocking of these motions by rigid taping such as with the McConnell tape would also appear to limit the conjunct talar external rotation that occurs with normal pronation during DF. Thus, this study used Kinesio taping to maintain joint alignment. However, this result could not prove that the Kinesio tape did work or not. Thus, future studies should examine the long-term effect of various GCM stretching techniques for controlling subtalar movement using both Kinesio and rigid taping in subjects with limited ankle DF and pronated feet.

This study has several limitations. First, owing to its cross-sectional design, this study could not determine the long-term effects of GCM stretching with talar self-stabilisation and GCM stretching with talar self-stabilisation and subtalar supination on ankle kinematics. Second, we measured only open-chain ankle DF ROM with the knee straight, open-chain ankle DF ROM with the knee bent, closed-chain ankle DF ROM with the knee straight, and ND. We did not measure other gait parameters such as heel-off time, although a previous study has reported that heel-off time was significantly earlier in subjects with limited ankle DF than in those without it [54]. Future studies should be conducted to investigate the long-term effects of GCM stretching with talar self-stabilisation and GCM stretching with talar self-stabilisation and subtalar supination on heel-off time during the gait cycle. Third, we were not blinded to the measurements; thus, investigator bias might have affected our results. The bias might have been more likely during the measurement of open-chain ankle DF ROM with the knee straight than during closed-chain measurement because we did not use a force controller to minimise errors, resulting from the application of unequal force. Future studies should use a force controller such as a handheld dynamometer.

5. Conclusions

This study investigated the immediate effect of GCM stretching alone, GCM stretching with talar self-stabilisation and GCM stretching with self-stabilisation and subtalar supination on open-chain ankle DF ROM with the knee straight, open-chain ankle DF ROM with the knee bent, closed-chain ankle DF ROM with knee straight and ND on subjects with limited ankle DF. The results showed that GCM stretching with talar self-stabilisation and subtalar supination produced a significantly greater open- and closed-chain ankle DF ROM than GCM stretching alone. Stabilisation of the talus by taping both at the talocrural and subtalar joints may restrict excessive foot pronation in subjects with limited ankle DF, leading to increased ankle DF. Thus, GCM stretching combined with talar self-stabilisation and subtalar supination is superior to GCM stretching alone in subjects with limited ankle DF, when performed immediately.

Footnotes

Conflict of interest

None to report.

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Combined effect of gastrocnemius stretching with self-stabilising talus during subtalar supination on ankle kinematics in subjects with limited ankle dorsiflexion

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSIONS:

Keywords

1. Introduction

Table 1 Subjects’ demographic information (mean ± SD)

2.1 Subjects

2.2 Procedure

2.3 Measurement of dependent variables

2.3.1 Open-chain ankle DF ROM with the knee straight

2.3.2 Open-chain ankle DF ROM with the knee bent

2.3.3 Closed-chain ankle DF ROM with the knee straight

2.3.4 ND test

2.4.1 GCM stretching alone

2.4.3 GCM stretching with talar self-stabilisation and subtalar supination

3. Results

4. Discussion

5. Conclusions

Footnotes

Conflict of interest

References

Table 1
Subjects’ demographic information (mean $\pm$ SD)