Increased plantar force and impulse in American football players with high arch compared to normal arch

Abstract

Background

Risk of overuse injury among athletes is high due in part to repeated loading of the lower extremities. Compared to individuals with normal arch (NA) structure, those with high (HA) or low arch (LA) may be at increased risk of specific overuse injuries, including stress fractures. A high medial longitudinal arch may result in decreased shock absorbing properties due to increased rigidity in foot mechanics. While the effect of arch structure on dynamic function has been examined in straight line walking and running, the relationship between the two during multi-directional movements remains unstudied.

Objective

The purpose of this study was to determine if differences in plantar loading in football players occur during both walking and pivoting movements.

Method

Plantar loading was examined in 9 regions of the foot for 26 participants (16 NA, 10 HA).

Results

High arch athletes demonstrated increased maximum force in the lateral rear foot and medial forefoot, and force time integral in the medial forefoot while walking. HA athletes also demonstrated increased maximum force in the medial rear foot and medial and central forefoot during rapid pivoting.

Conclusions

The current findings demonstrate that loading patterns differ between football players with high and normal arch structure, which could possibly influence injury risk in this population.

Introduction

Risk of lower extremity injury among young athletes is related to a variety of internal and external factors. It has been suggested that repeated impacts with the ground, coincident with the resultant ground reaction forces, can initiate numerous lower extremity injuries, including stress fractures [1], cartilage damage [2] and the development of osteoarthritis [3], [4], amongst others. Anatomical differences in foot, including abnormal arch structure, increase the risk of lower extremity overuse injuries two-fold [5]. Athletes with both high and low arches may be at increased risk of lower extremity injury compared to athletes with normal arches [5], [6], [7]. A high medial longitudinal arch may increase rigid foot mechanics that result in decreased shock-absorbing properties when compared to athletes with normal arch structure [5], [8], [9]. Specifically, decreased motion (increased stiffness) between multiple segments within the foot has been shown among individuals with high arch structure [10]. An increased relative arch height is also linked to increased risk of multiple lower extremity injuries, including plantar fasciitis and lateral ankle sprains [9]. Furthermore, the biomechanical coupling of foot eversion-inversion with tibial internal-external rotation may also increase the risk of knee injury in athletes with a high arch [11].

Foot structure can be objectively assessed with a variety of clinical and research tools [12], [13], [14], [15]. For example, the arch height index measurement system (AHIMS) is a non-invasive, easy to use device that is a reliable and valid method of measuring the foot structure [9], [14], [16], [17]. Objective measurement could provide an effective tool for clinicians to identify an athlete's relative predisposition to injury [11].

Comparison of foot structure to dynamic function has been evaluated primarily during straight-line walking and running [7], [10], [11], [12], [18], [19], [20], [21], [22], [23], with findings of changes in loading [12], [20], [22] and kinematic aspects of movement [11] among those with varying arch structures. The current literature indicates that further insight into injury mechanisms among athletes with abnormal arch height could result by evaluation of dynamic loading activities in shod conditions [10]. Specifically, differences in plantar loading between straight line tasks and multi-directional movements have been previously demonstrated in shod conditions. For example, when compared to running, individuals performing a side cut have demonstrated increased values on the medial aspect of the foot in peak pressure [23], [24], pressure time integral [23] and percent of total load of the foot [24].

Shoe design for football may consist of different cleat patterns, cushioning characteristics and a vast variety of materials. The requirements for the sport and position often require different design considerations. For American football, cutting maneuvers are frequent and have been previously examined [25], [26]. Ford et al. [26] compared a football cleat on multiple surfaces (synthetic and natural) and found significantly greater forefoot loading on the natural grass surface. Interestingly, the lateral aspect of the foot had greater peak pressure on a synthetic surface compared to natural surface when cutting with cleated footwear [26]. Oredurff et al. [25] identified similar pressure distribution patterns when wearing a similar cleat used in Ford et al. [26]. Several additional movements were examined and compared across different cleat patterns. The relationship between cushioning and support during cutting may be considered a challenging design feature in American football cleats. Additional questions are likely raised due to individual variation of foot structure, specifically arch height. Therefore, the purpose of the current study was to determine if loading patterns were different among high school football players with different arch structures. We hypothesized that individuals with a high arch would have increased plantar loading relative to individuals with a normal arch during barefoot walking and dynamic cutting activities while wearing sport-specific footwear.