Dynamic loading and kinematics analysis of vertical jump based on different forefoot morphology
© The Author(s) 2016
Received: 30 May 2016
Accepted: 14 November 2016
Published: 22 November 2016
This study examined differences in ankle motion and plantar pressure between habitually barefoot male (HBM) and habitually shod male (HSM) during vertical jump.
Eighteen habitually barefoot males and twenty habitually shod males volunteered to join the test. Distance between hallux and second toe was measured with Easy-Foot-Scan. Plantar pressure and ankle kinematics were measured with EMED force platform and Vicon motion analysis system respectively. T test was taken to analyse the significant differences using Stata 12.0 software.
The distance between hallux and other toes in HBM was greater than it in HSM. HBM showed larger plantar loading under hallux and medial forefoot, while HSM showed lager plantar loading under medial and central forefoot. HBM had smaller ankle plantarflexion, eversion and external rotation than HSM.
Findings of this study provide basic information for further studies on different hallux/toe function in motion control between habitually shod and barefoot populations.
Human is bipedal species using two feet to stand and move. Franklin et al. (2015) considered that human feet took the effort of balance and movement control. Morphological differences in foot could cause many foot malfunctions, disorders and deformity (Ledoux et al. 2003). Furthermore, foot morphology had a close relationship with areas: forefoot and toes have been reported to be the prominent target areas (Lambrinudi 1932; Rolian et al. 2009; Hoffmann 1905; D’AoÛt et al. 2009). Wolf et al. (2008) found that acquired behaviour such as footwear wearing may lead to foot structure deformation, such as flatfoot and hallux valgus. Toe separation of habitually barefoot populations showed to be more obvious compared with habitually shod populations (Wolf et al. 2008). In addition, previous studies indicated that habitually barefoot individuals were less likely to be injured than habitually shod ones during running (Robbins and Hanna 1987; Robbins et al. 1988). Lieberman et al. (2010) ascribed this difference to different foot strike patterns. Clinical research presented that metatarsal pathologies were more critical in habitually shod populations than in habitually barefoot populations (Zipfel and Berger 2007).
Jumping as a fundamental motion in sports frequently leads to lower limb injuries, primarily due to the rapid shock to lower limbs at landing (Vint and Hinrichs 1996; Doherty et al. 2014). Ankle sprain has been considered as one of the most common injuries in various sports with frequent jump motion such as volleyball, basketball and soccer. According to the survey, there are approximately 5600 incidences of ankle sprain per day in the UK, a mere between 3 and 5% of all Emergency Department visits (Pijnenburg et al. 2000). Larger plantar loading at forefoot and toes areas in take-off and landing may increase the risk of metatarsal injuries. However, whether there are differences in ankle motion and plantar loading between habitually barefoot populations and habitually shod populations in jumping remained to be unclear.
Therefore, the purpose of the study was to investigate difference in ankle kinematics and plantar pressure under forefoot and toes regions between habitually shod male (HSM) and barefoot male (HBM) during vertical jump based on different forefoot morphology. It was hypothesised that HBM and HSM would present different ankle motions (ankle variation angles and maximal or minimal angles) and plantar pressure characteristics related to different hallux and second toe separation.
Descriptive statistics for age, height, mass, and foot length
Habitually barefoot males (N = 18)
Habitually shod males (N = 20)
24 ± 1.2
24 ± 2.1
165.3 ± 1.2
172.1 ± 1.6
65.4 ± 6.9
66.2 ± 6.5
23.88 ± 0.93
22.31 ± 1.97
Right leg length (cm)a
86.5 ± 2.8
89.3 ± 3.9
Right feet length (cm)
25.5 ± 1.4
25.5 ± 0.9
Before test, each participant was required to warm up for 5 min. Then participants performed countermovement jump from a suitable pre-squatting motion under barefoot condition. Participants were required to keep their hands on hips in every vertical jump to reduce the energy through the torso activities. Each participant performed five trials, with resting 30 s to avoid fatigue.
Data for analysis were extracted during the taking-off and landing phase. Take-off phase is defined as the period from knee joint starting to flexion to the foot taking off the ground. The instant of take-off is defined as the moment that the vertical ground reaction force closing to 0 N. Landing phase is defined as the period from the foot touching the ground to total knee extension. The instant of landing is defined as the moment that the vertical reaction force higher than 0 N.
All statistical analyses were performed using Stata 12.0 software. The t-test was taken to analysis the significance of jump height, ankle variation range, peak pressure, contact area and pressure–time integral. Significance level P < 0.05 is defined as statistical difference.
There were no significant differences found in jump height between HBM and HSM (HBM: 0.39 ± 0.11 m; HSM: 0.40 ± 0.13 m, P > 0.05).
Comparison of ankle variation range during two phases between HSM and HBM (mean ± SD)
60.85 ± 1.43*
68.25 ± 2.80*
42.45 ± 2.14*
60.40 ± 7.02*
3.16 ± 1.49*
6.96 ± 1.49*
3.29 ± 0.34*
6.19 ± 1.49*
20.24 ± 2.47
22.36 ± 6.74
20.00 ± 1.33
18.66 ± 4.67
At the moment of take-off, HBM showed significantly larger plantarflexion than that of HSM (P < 0.001). HBM showed to be inversion while HSM showed to be eversion at this moment (P < 0.001). HBM showed significantly smaller external rotation than HSM (P < 0.001). At the moment of landing, HBM showed significantly smaller eversion and external rotation than HSM (eversion: P < 0.001, external rotation: P < 0.001).
Comparison of plantar pressure between HBM and HSM (mean ± SD)
Pressure–time integral (Kpa*s)
54.88 ± 15.26*
34.50 ± 11.76*
40.57 ± 7.74*
32.71 ± 11.09*
20.54 ± 5.10
22.70 ± 8.03
19.40 ± 4.41
21.01 ± 3.89
39.36 ± 8.77*
47.75 ± 14.71*
33.50 ± 3.20*
37.07 ± 4.76*
18.59 ± 6.14*
27.66 ± 10.81*
21.47 ± 7.46*
27.43 ± 9.50*
13.02 ± 1.56
13.83 ± 4.53
15.11 ± 1.24*
17.25 ± 4.44*
Peak pressure (Kpa)
649.50 ± 260.09*
267.86 ± 69.11*
391.88 ± 188.61*
287.14 ± 71.07*
248.30 ± 86.50
242.14 ± 37.70
219.38 ± 68.13
207.14 ± 66.16
393.50 ± 135.44*
552.14 ± 241.49*
295.63 ± 123.74
295.00 ± 84.23
138.50 ± 71.36*
242.14 ± 124.66*
138.13 ± 53.76*
221.43 ± 88.43*
85.00 ± 44.32
102.86 ± 52.83
101.88 ± 35.19*
128.58 ± 54.75*
Contact area (cm2)
8.88 ± 1.67
8.40 ± 0.80
7.53 ± 2.04
7.02 ± 2.05
8.57 ± 1.80
8.69 ± 1.43
6.94 ± 1.67*
5.57 ± 0.46*
13.98 ± 1.72*
12.45 ± 1.75*
13.29 ± 1.70
12.83 ± 1.50
15.58 ± 2.79
14.13 ± 5.95
17.25 ± 2.37*
20.87 ± 2.14*
8.79 ± 3.49
7.43 ± 3.89
11.43 ± 3.33
11.13 ± 1.15
During landing phase, for pressure–time integral, significant differences were found between HBM and HSM in H, MF, CF and LF. HBM showed higher pressure–time integral than HSM in H (P = 0.0132), while HSM showed higher pressure–time integral than HBM in MF, CF and LF (MF: P = 0.0083; CF: P = 0.0335; LF: P = 0.0447). For peak pressure, significant differences were found in H, CF and LF. HBM showed higher peak pressure than HSM in H (P = 0.0075). HSM showed higher peak pressure than HBM in CF and LF (CF: P < 0.001; LF: P = 0.0256). For contact area, significant differences were found in OT and CF. HBM showed larger contact area than HSM in OT (P = 0.0011). HSM showed larger contact area than HBM in CF (CF: P < 0.001).
Previously published researches have proved forefoot morphological difference between HBM from India and HSM from China that HBM have more obvious hallux and the second toe separation compared with HSM (Shu et al. 2015; Mei et al. 2015). This study verified differences in ankle kinematics and plantar loading between the two populations in vertical jump. HBM presented significantly larger plantar loading than HSM under hallux, which may be associated with the fact that hallux of HBM was significantly separate from other toes (Ashizawa et al. 1997). Differences in ankle motions also showed significance between HBM and HSM. However, no significant difference in jump height between two groups was observed.
During take-off phase, significant differences in pressure–time integral and peak pressure between HBM and HSM were under plantar regions of H, MF and CF. During landing phase, differences existed under hallux and forefoot. In this case, it further concluded that plantar loading of HBM was large under H and MF, while the pressure of HSM was large under MF and CF. Previous findings in relation to barefoot running suggested that HBM have distinctive features in push-off phase, which may be caused by the more separated toes of this population that could expand and firm the supporting base in gripping (Hoffmann 1905; Wolf et al. 2008; Ku et al. 2012). Since HBM used hallux while HSM used forefoot primarily during take-off, the significantly larger plantarflexion of HBM than HSM could be explained partly. Similarly, the larger ankle variation range of ev-inversion and int-external rotation of HSM conformed to kinetic results that peak pressure of HSM tended to shift laterally compared with HBM. Moreover, Salinero et al. stated that although increased ankle dorsiflexion could affect muscle activation, it would not improve jump performance (Salinero et al. 2014). This is consistent with the result in this study that HBM and HSM showed comparable jump height with different ankle position in the sagittal plane.
During landing phase, HBM showed larger plantarflexion but smaller eversion and external rotation than HSM. These were in line with the kinetic results that HBM showed larger peak pressure under hallux while smaller pressure under central and lateral forefoot. This suggested different functions of the hallux in motion control between HBM and HSM. Mei et al. (2015) also reported larger loading under the hallux among HBM during running, which may reduce impact force to forefoot area.
Ankle sprain is a common lower limb injury in sports, especially during landing phase in jump. Foot rotation has been reported as a principal factor for ankle sprain in clinical literature (Hopkinson et al. 1990). Previous studies have demonstrated that ankle injuries are associated with combined ankle motions of dorsiflexion, eversion and external rotation (Williams et al. 2007; Taylor and Bassett 1993; Wolfe et al. 2001). In this study, HBM showed smaller eversion and external rotation than HSM, indicating that HBM are at lower risk of ankle sprain compare with HSM (Rolian et al. 2009; Robbins and Hanna 1987). On the other hand, Novacheck (1998) and Tam et al. (2014) stated that excessive loading under metatarsal heads would lead to forefoot injuries such as metatarsal fracture. The larger peak pressure under metatarsal heads areas (MF, CF and LF) of HSM observed in this study indicated a higher risk of forefoot injuries among this population.
HBM and HSM showed different ankle motions and plantar loading in vertical jump, which is potentially due to forefoot morphological difference in the distance between hallux and the second toe. HBM showed larger ankle plantarflexion with smaller eversion and external rotation compared with HSM. Additionally, HBM showed larger plantar loading under hallux and medial forefoot, while HSM showed larger plantar loading under medial and central forefoot. Findings of this study provide basic information for further studies on different hallux/toe function in motion control between habitually shod and barefoot populations.
YS, YZ and LF collected all data, YS, JB, JL and YG drafted the manuscript. YS, GF and YZ performed the statistical analyses, YS, YZ and YG participated in the design and coordination and helped drafting the manuscript. All authors read and approved the final manuscript.
This study sponsored by Zhejiang Social Science Program ‘Zhi Jiang youth project’ (16ZJQN021YB), National Natural Science Foundation of China (81301600), K. C. Wong Magna Fund in Ningbo University, National Social Science Foundation of China (16BTY085), Loctek Ergonomic Technology Corp, and Anta Sports Products Limited.
The authors declare that they have no competing interests.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
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