The purpose of this study was to determine the optimal inner-shoe volume for children tennis players. Sixteen participants, aged from 8 to 12 years old assessed comfort of 6 shoes, which were a combination of 3 lasts (thin, medium and wide) and 2 upper constructions (flexible and stiff), while a sock equipped with textile sensors was measuring the pressure applied on their foot. The thin last was based on the proportion of an adult last. The widest shoes produced the lowest pressure on the 1st and 5th metatarsal heads, the medial midfoot and the medial and lateral heel (p < 0.05), whilst they were perceived the most comfortable for the 3rd and 5th metatarsal heads, the 5th metatarsal base and the medial and lateral heel (p < 0.05). These outcomes indicated that footwear manufacturers should design wider shoes for children than for adults.

Worldwide, tennis is practiced by millions of children, several thousands being intensive players. The participation in high-performance training programmes and competition places them at risk to e...

Athletic children are prone to overuse injuries, especially at the heel and knee. Since footwear is an extrinsic factor of lower limb injury risk, the aim of this study was to assess the influence of shoe aging on children running biomechanics. Fourteen children active in sports participated in a laboratory biomechanical evaluation. A new pair of shoes was provided to each participant at an inclusion visit. Four months later, the participants performed a running task and their kinematics and kinetics were assessed both with their used shoes and with a new pair of shoes identical to the first. Furthermore, mechanical cushioning properties of shoes were evaluated before and after in-vivo aging. After 4 months of use, the sole stiffness increased by 16% and the energy loss capacity decreased by 18% (p < 0.001). No ankle or knee kinematic adjustment was found at foot strike in used shoes but changes were observed later during stance. Running with used shoes produced a higher loading rate of the vertical ground reaction force (+ 23%, p = 0.016), suggesting higher compressive forces under the heel and placing children at risk to experience impact-related injuries. Nevertheless, the decreased peak ankle and knee power absorption in used shoes (-11%, p = 0.010 and -12%, p = 0.029, respectively) suggests a lower ankle and knee joints loading during the absorption phase that may be beneficial regarding stretch-related injuries.

"Correlation between foot pressure and comfort in recreational and advanced tennis players." Footwear Science, 9(sup1), pp. S15–S16

Compared to traditional tennis shoes, using 0-drop shoes was shown to induce an immediate switch from rear- to forefoot strike pattern to perform an open stance tennis forehand for 30% of children tennis players. The purpose of the study was to examine the long-term effects of a gradual reduction in the shoe drop on the biomechanics of children tennis players performing open stance forehands. Thirty children tennis players participated in 2 laboratory biomechanical test sessions (intermediate: +4 months and final: +8 months) after an inclusion visit where they were randomly assigned to control (CON) or experimental (EXP) group. CON received 12-mm-drop shoes twice, whereas EXP received 8 mm then 4-mm-drop shoes. Strike index indicated that all CON were rearfoot strikers in intermediate and final test sessions. All EXP were rearfoot strikers in intermediate test session, but half the group switched towards a forefoot strike pattern in final test session. This switch resulted in a decreased loading rate of the ground reaction force (-73%, p = .005) but increased peak ankle plantarflexors moment (+47%, p = .050) and peak ankle power absorption (+107%, p = .005) for these participants compared with CON. Biomechanical changes associated with the long-term use of partial minimalist shoes suggest a reduction in heel compressive forces but an increase in Achilles tendon tensile forces.

This study investigated the immediate effects of reducing the shoe drop (i.e. the difference between the heel and the forefoot height) on the kinematics and kinetics of the lower extremities of children tennis players performing a tennis-specific movement. Thirteen children tennis players performed a series of simulated open stance forehands wearing 3 pairs of shoes differing only in the drop: 0 (D0), 6 (D6) and the control condition of 12 mm (D12). Two embedded forceplates and a motion capture system were used to analyse the ground reaction forces and ankle and knee joint angles and moments of the leading lower limb. In D6 compared with D12, the peak impact force was reduced by 24% (p = .004) and the ankle was less dorsiflexed at foot strike (p = .037). In D0 compared with D12, the peak impact force was reduced by 17% (p = .049), the ankle was less dorsiflexed at foot strike (p = .045) and the knee was more flexed at foot strike (p = .007). In addition, 4 out of 13 participants (31%) presented a forefoot strike pattern for some of the trials in D0. No difference was observed across shoe conditions for the peak knee extensor moment (p = .658) or the peak ankle plantarflexor moment (p = .071). The results provide preliminary data supporting the hypothesis that for children tennis players, using a 6-mm lower shoe drop might reduce heel impact forces and thus limit potentially impact-related injuries.

"Lower shoe drop can reduce impact forces experienced by junior tennis players performing an open-stance forehand." Footwear Science, 7(sup1), pp. S112–S113

Objective. - The aim of this study was to determine the influence of ground reaction forces on the footwear stability.Material and methods. - Twelve healthy men have walked on a treadmill ergometer ADAL with five different shoe models and in a barefoot condition. Here, the shoe called "shoe 1" is known for its capacity to stabilize the foot. Ground reaction forces (F(x), F(y), F(z)) were recorded at constant speed (2, 4 and 6 km h(-1)), and during transition phases (0 to 2, 0 to 4, 0 to 6 km h(-1)). Two running conditions (8 km h(-1) at constant speed and 0 to 8 km h(-1) in transition) have completed this protocol. Then, each subject filled in a questionnaire to evaluate, for each shoe, different sensations: stability during walking and running, foot support, heightening of the rearfoot, width of shoe at the heel, general comfort, cushioning. At last, different geometrical parameters of each shoe were measured.Results and discussion. - The results show that, in all tested conditions (constant speed and transition phases, walking and running), medial force peaks are significantly more important in barefoot condition than all shod conditions, except for the shoe 1. As the barefoot condition is, according to the literature, the best condition of stability and as the shoe I is known for its capacity to stabilize the foot, these results could suggest that a better stability could be associated with more important medial force peaks. (C) 2008 Elsevier Masson SAS. Tous droits reserves.

The objective of this study is to determine if Ground Reaction Forces (GRF) could be linked to the stability of the shoe. For this, kinetics data (GRF) have been extracted during locomotion in different conditions (shod and barefoot conditions). Currently, stability is evaluated with 2D or 3D film analysis, or with the study of Center of Pressure path. This paper determines if another biomechanical parameter could be used to quantify the stability. 12 subjects (177.9cm ± 4.29, 23.3 years old ± 4.29, and 710.1N ± 78.45) walked on a treadmill ergometer ADAL wearing 5 different shoes models. A barefoot situation was added to the protocol, according to the literature as the best condition of stability ([2]; [3]) 2 data sets were recorded: GRF (Fx, Fy, Fz) were recorded at constant speed (CS) of 2, 4 and 6 km.h-1, and during transition phases (0 to 2, 0 to 4, 0 to 6 km.h-1). Transition phases (TP) were studied because gait transitions are characterized by a loss of stability [1]. Two running conditions (8 km.h-1 at CS and 0 to 8 km.h-1 at transition) have completed this protocol. At CS, forces were recorded on 10 steps. In TP, maximal force peaks were retained. Geometrical parameters of the shoe were measured: heel counter dimensions, different widths of the sole, sole slopes, heights of upper on external malleolus These 2 data groups were crossed with correlation matrix. Results show significant differences between barefoot condition and all the shod conditions, except for the shoe 1. In barefoot and with the shoe 1, medial forces peaks are more important. During TP, the same differences are relieved. In the running condition, the same results are observed: medial forces peaks are significantly more important in the barefoot condition and with the shoe 1 than the other shoes. Several works of Stacoff ([2]; [3]) have determined that the best condition of stability is in barefoot condition; so the results of this study could suggest that a better stability would be translate by medial forces peaks more important. This conclusion could be reinforced by the fact that the shoe 1, known for its capacity to stabilize the foot, is not significantly different of the barefoot condition. Correlations between GRF data and shoe measurements brought to the conclusion that there are different parameters of the shoe which could influence the stability: if greater medial forces peaks translate a better stability, a low sole slope, and a more important height of upper on external malleolus increase the stability. The stability seems to be characterized by a more important medial force. It could be interesting to complete this work with other shoes in the aim of completing these data. In addition, further investigations could be suggested to correlate these preliminary results with a method known to evaluate the stability. These works will comfort or not the importance of the GRF in the evaluation of the stability of a shoe. [1] Diedrich, F.J. and Warren, W.H. Jr. Why change gaits? Dynamics of the walk-run transition. Journal of Experimental Psychology: Human Perception and Performance. 21 (1): 183-202, 1995. [2] Stacoff, A., Kaelin, X. and Stuessi, E. The effect of shoes on the torsion and rearfoot motion in running. Medicine and Science in Sports and Exercise. 23 (4): 482490, 1991. [3] Stacoff, A., Steger, J., Stuessi, E. and Reinschmidt, C. Lateral stability in sideward cutting movements. Medicine and Science in Sports and Exercise. 28 (3): 350-358, 1996.

The aim of this study is to determine if ground reaction forces (GRF) could be a significant parameter to evaluate the stability of the shoe. According to Forner Cordero (2003), the stability of an object is its capacity to maintain a balance and to resume its position (or sway) after a disturbance. So the stability of the shoe can signify its capacity to limit involuntary imbalances of the foot and of the ankle. Here, kinetics data (Fx, Fy and Fz for each foot) have been extracted during locomotion in different conditions (shod and barefoot conditions). Currently, stability is evaluated with 2D or 3D film analysis, or with the study of center of pressure path. This paper determines if another biomechanical parameter could be used to quantify the stability.

Objective: This paper investigates the influence of footwear geometry on ground reaction forces (GRF) and perception of stability during locomotion.