Correlation of ankle dorsiflexion range of motion with lower-limb kinetic chain function and hop test performance in healthy male recreational athletes

Open-chain ADROM

The Modified Root protocol was used to evaluate the passive ADROM for both lower limbs (Rowlett et al., 2019). A universal goniometer (Elite Medical Instruments, Fullerton, CA, USA) was the tool to evaluate open-chain/non-weight-bearing ADROM in knee-angle-based positions: with the knee in 0-degree extension (position 1) and with the knee in 90 degrees flexion (position 2) (Rowlett et al., 2019) as illustrated in Fig. 1. The goniometer axis was put on the lateral malleolus. One goniometer arm was aligned with the fibula, indicating toward the fibular head. The other arm was put parallel to the fifth metatarsal longitudinal axis. The body landmarks were marked to have an accurate measurement (Weaver, 2001; Fong et al., 2011; Krause et al., 2011; Rowlett et al., 2019). One tester (the principal investigator) completed the joint ROM measurement because the assessment of the joint ROM with a universal goniometer has been shown to have greater intra-tester than inter-tester reliability (Boone et al., 1978).

Gastrocnemius and soleus extensibility (weight-bearing ADROM with knee flexion/extension)

Muscle extensibility was measured by the universal goniometer (illustrated in Fig. 2) using the weight-bearing/closed-chain ADROM. The soleus extensibility was measured using the weight-bearing ADROM with knee flexion. The gastrocnemius extensibility was measured using the weight-bearing ADROM with knee extension (Encarnación-Martínez et al., 2020).

Similar anatomical landmarks and universal goniometer arms placement were used for open-chain ADROM and extensibility (for gastrocnemius and soleus) testing. The universal goniometer stationary arm was placed on a marked fibular distal long axis (a line linking the center of the lateral malleolus with the center of the fibula head) (Worrell, McCullough & Pfeiffer, 1994). While the moveable arm of the universal goniometer was placed parallel to the fifth metatarsal for the open-chain measurements, it was placed parallel to the floor for the weight-bearing measurements (Worrell, McCullough & Pfeiffer, 1994). The ADROM was recorded from each participant using the methods mentioned above during three trials, and the average ROM reading was calculated (Rowlett et al., 2019).

Lower-limb performance tests

CKC lower-extremity stability test (CKCLEST)

A stable base floor, mat, and stopwatch were the tools used to perform CKCLEST. The starting position of the CKCLEST was the plank position using the support of the forearms with the feet shoulder-width apart, the toes were in contact with the ground, and the body was in a straight line. While maintaining this initial body position, the athlete was asked to cross the outer side of the other foot with one foot and return. Then, the athlete made the same cross-and-return movement using the other foot. The athlete did this movement with both feet alternatively as fast as possible, as illustrated in Fig. 3. The number of repetitions in 15 s was recorded by counting the number of times the foot touched the other foot’s lateral side and the floor. Three repetitions of the 15-second CKCLEST were performed with an interval of one minute between each test. Each athlete was allowed to perform the test once as a trial to be familiar before the actual test. Three trials were done, and the best trial score was used in the data analyses (Arikan et al., 2021).

Single leg hop for distance test (SHDT)

The athlete stood on the test lower limb and then hopped as far as he could and landed on the same lower limb with no extra hops until two-to-three seconds, as illustrated in Fig. 4. Then the investigator measured the distance (in centimeters using a tape measure) from the big toe at the push-off to the heel at the landing (Gustavsson et al., 2006). Single leg hop for distance test was accomplished with arms behind the back because it is the most sensitive procedure to identify poor functional performance (Ageberg & Cronström, 2018). A coin-flip governed which lower limb the athlete hopped with first (Brumitt et al., 2013). The single-legged hop test was executed barefoot (Harrison et al., 2017). The test was performed three times alternatively between the right and left lower limb (Ageberg & Cronström, 2018). The best distance achieved was the score needed for data analysis.

Side hop test (SHT)

The athlete stood on the tested leg, with hands behind the athlete’s back, and jumped from side to side between two parallel tape strips (with a 40-centimetre distance between them), as illustrated in Fig. 5. The athlete was directed to jump as many times as he could throughout 30 s. The successful jumps repetition (without touching the tape) was documented (Gustavsson et al., 2006). The test was performed for three trials alternating the trials between lower limbs. The test was executed barefoot (Harrison et al., 2017). The best score (the one with the highest repetition) was the score needed for data analysis.

The CKCLEST and SHT correlation

The correlation between the CKCLEST and SHT was positive and significant for the dominant and non-dominant lower limbs. To the best of our knowledge, this is the first study to find this correlation. The quick side hop performance was found to reflect hip function in terms of hip flexion, extension, and abduction torque in competitive sports performers (Ono et al., 2021). Moreover, hip abduction torque was a core stability booster while executing the single-leg side-stepping (Inaba et al., 2013). Therefore, there is a possibility that the SHT-related lower-limb biomechanical constructs mimic those of the CKCLEST.

The study presented preliminary data about the prevalence of decreased ADROM. Regarding the open-chain ADROM with knee extension, the study found that 17 out of the 21 participants (81%) have less than normal in dominant and non-dominant lower limbs (the normal ADROM with knee extension is 20 degrees (Coetzee & Castro, 2004)). As for compatibility with this findings, it was found (in a previous study) that young male soccer players may manifest a marked and early decrease in open-chain ADROM with knee extension from the first few years of practicing sports activities (Francia et al., 2021). For the open-chain ADROM with knee flexion, 15 out of 21 participant (71%) have decreased range in the dominant lower limb (the normal ADROM with knee extension is 35 degrees (Baumbach et al., 2016)). In the non-dominant lower limb, 17 out of the 21 participants (81%) were with decreased range.

In the study sample, the weight-bearing closed-chain ADROM with knee flexion (representing the soleus extensibility) was decreased in 16 out of 21 participants (76%) in the dominant lower limb and in 16 out of 21 participants (76%) had decreased range in the non-dominant lower limb. The normal weight-bearing closed-chain ADROM with knee flexion is 43 degrees (Baumbach et al., 2016). For the weight-bearing closed-chain ADROM with knee extension (representing the gastrocnemius extensibility), there were 20 out of 21 participants (95%) with a decreased range in the dominant lower limb. Likewise, 20 out of 21 participants had decreased range in the non-dominant lower limb. The normal weight-bearing closed-chain ADROM with knee extension is 34 degrees (Baumbach et al., 2016). Therefore, the study participants had a high prevalence of triceps surae decreased extensibility (in gastrocnemius more than soleus).

The possible explanation of the decreased ADROM to less than normal in the study participants can be made clear with the following correlations. In the study participants, a positive and significant (rho = 0.504, 95% CI [0.079–0.774], P = 0.02) correlation was found between the soleus extensibility and open-chain ADROM with knee extension of the dominant lower limb. Similarly, in the non-dominant lower limb, the correlation was positive and highly significant with soleus (r = 0.705, 95% CI [0.393–0.871], P < 0.001) and gastrocnemius extensibility (r = 0.609, 95% CI [0.240–0.824], P = 0.003). Likewise, in the dominant and non-dominant lower limbs, the correlation between the soleus extensibility and open-chain ADROM with knee flexion was positive (r = 0.702, 95% CI [0.387–0.870], and 0.812, 95% CI [0.525–0.906], respectively) and highly significant (P<0.001). In the dominant and non-dominant lower limbs, the correlation between gastrocnemius extensibility and open-chain ADROM with knee flexion was positive (r = 0.567, 95% CI [0.179–0.802], and 0.805, 95% CI [0.572–0.918], respectively) and highly significant (P = 0.007 and P < 0.001, respectively). Moreover, it was found in a previous study (Guillén-Rogel, San Emeterio & Marín, 2017) that there was a significant positive link between the ADROM and ankle dorsiflexors strength in young and healthy male students. So, it can be derived that decreased ADROM is possibly linked to decreased plantar flexors’ (soleus and gastrocnemius) extensibility and dorsiflexors’ strength.

Knowing that the sports-related repetitive movements can shorten and thicken the fascia around the overused muscles (De Witt & Venter, 2009), affecting their extensibility. Therefore, the decreased soleus and gastrocnemius extensibility in the study sample can be referred to their extensive use in sports as confirmed in the following lines. In the running, just before the toe-off phase, the soleus and gastrocnemius absorb the peak mechanical power (Sasaki & Neptune, 2006). This peak power absorption increases when the ankle dorsiflexion is decreased (Pope, Herbert & Kirwan, 1998; Kaufman et al., 1999). Furthermore, in fast arm movements, the muscle activation sequence starts in the contralateral gastrocnemius (Zattara & Bouisset, 1988) and then through the core and thoracolumbar fascia reaches up to the arm (Cordo & Nashner, 1982; Hirashima et al., 2002). The ankle is a key joint to perform optimal vertical jumping (Kilic et al., 2017). In the jumping take-off phase, the mechanical energy flows through the ankle joint that is adapting its plantarflexion motion making 23% of the velocity (Hubley & Wells, 1983), which is dependent on the force amount generated by the gastrocnemius muscle (Bobbert & van Zandwijk, 1999). In landing from a jump, the gastrocnemius-soleus complex provides 44% of the energy absorption total muscle work (Devita & Skelly, 1992) and slows the ground reaction forces propagation speed to the knee (Boden et al., 2010).

On the other hand, in the study sample, it was found that 19 out of 21 participants (90%) had passive ankle plantarflexion ROM that is above the normal range in the dominant lower limb with mean of 66.3 degrees. Moreover, we found that all participants have beyond normal ankle plantarflexion ROM in their non-dominant lower limb, with a mean of 68.3 degrees. The normal plantarflexion passive ROM is 50.0 degrees (Alazzawi et al., 2017).

For the dominant lower limb, this finding can be justified when the study found a positive and highly significant correlation between the time spent practicing the main sport per day and passive ankle plantarflexion ROM in the dominant lower limb (r = 0.677, 95% CI [0.346–0.858], P < 0.001). This correlation was weak and non-significant (r = 0.280, 95% CI [−0.172–0.635], P = 0.218) in the non-dominant lower limb. The study participants’ main sports involve many stretch-shortening activities (e.g., running, sprinting, side hopping, and vertical jumping). Previous studies (INal, Erbuğ & Kotzamanidis, 2012; Sugiyama et al., 2014) confirmed the relationship between the dominant lower limb higher ankle plantarflexion ROM and the stretch-shortening activities’ performance in young and healthy male athletes. A previous study (INal, Erbuğ & Kotzamanidis, 2012) found that the 100-meter sprint running time was positively and significantly correlated with the ankle plantarflexion ROM in the dominant lower limb in young, healthy male sprinters. Likewise, it was found in collegiate young, healthy male basketball players during the running-single-leg-jumps that the ankle plantarflexion joint angles were significantly higher in the dominant than the non-dominant lower limb during the take-off phase (Sugiyama et al., 2014). It was found that the take-off phase higher ankle plantarflexion angles were linked with the effective ability to transfer the velocity of the run-up phase to higher jump height (Sugiyama et al., 2014). In side-hopping, at the end of the contact phase and preparation of the flight phase, the gastrocnemius-soleus muscle complex contract strongly to lift the body weight upwards (Yoshida, Taniguchi & Katayose, 2011). This strong contraction produces a fast ankle plantarflexion that has to be controlled by the tibialis anterior to properly adjust the ankle position (Yoshida, Taniguchi & Katayose, 2011).

Additionally, activities like kicking the ball that is repetitively practiced in football code sports demand more plantarflexion ROM and no dorsiflexion (Líška et al., 2021). Furthermore, it was found that young, healthy recreational athletes with decreased weight-bearing ankle dorsiflexion ROM with knee flexion (the mean was 36.3 degrees) tended to acquire greater ankle plantar flexion and knee extension at initial landing contact in young, healthy recreational athletes (Howe et al., 2019). Therefore, it can be derived that the increased ankle plantarflexion ROM in the study participants was possibly related to the time spent per day practicing stretch-shortening activities and decreased plantar flexors’ (gastrocnemius and soleus) extensibility.

From the above mentioned discussed information about ADROM and ankle plantarflexion findings in the study sample, it can be derived that the possible explanation of the participants’ increased range of ankle plantarflexion and decreased ADROM is linked to the sports-practice imposed musculoskeletal maladaptation and insufficient recovery after the training. The study is the first to have preliminary information about the prevalence of increased ankle plantarflexion ROM, decreased ankle dorsiflexion ROM, and decreased soleus and gastrocnemius muscle extensibility among healthy young recreational male athletes in Saudi Arabia. No such previous study was done in Saudi Arabia.

The ankle ROM correlation between dominant and non-dominant lower limbs

In terms of ankle plantar flexion ROM, the study found that the dominant and non-dominant lower limbs are weakly and non-significantly correlated (r = 0.398, 95% CI [−0.041–0.708], P = 0.074). However, the ADROM was positively, strongly, and significantly correlated between the dominant and non-dominant lower limbs. In details, for open-chain ADROM with knee flexion (r = 0.703, 95% CI [0.389–0.870], P < 0.001) and with knee extension (rho = 0.606, 95% CI [0.223–0.827], P = 0.004). For weight-bearing closed-chain ADROM with knee flexion (r = 0.782, 95% CI [0.529–0.908], P < 0.001) and knee extension (r = 0.852, 95% CI [0.664–0.938], P < 0.001). As for compatibility with such findings of the current study, a previous study found a positive and significant correlation between non-weight-bearing and weight-bearing ADROM with knee flexion on the dominant and non-dominant lower limbs (Rabin et al., 2014).

From a joint motion perspective, the ankle dorsiflexors and plantar flexors are crucial (Lauber, Gollhofer & Taube, 2018). However, during functional activities, the soleus (plantar flexor) is a high-force producer, while the tibialis anterior (dorsiflexor) generates lower forces (Lieber & Fridén, 2000). The training-related brain cortical adaptation is more optimal for the most proficient/dominant limb (Farthing, 2009). Moreover, previous studies’ findings (INal, Erbuğ & Kotzamanidis, 2012; Sugiyama et al., 2014) proved the relationship between the dominant lower-limb higher ankle plantarflexion ROM and stretch-shortening activities’ performance in young, healthy male athletes. So, since the dominant lower-limb plantar flexors are more proficient in producing force to help execute the activity, the ankle plantarflexion ROM may become uncorrelated between the dominant and the non-dominant lower limb.