# Development of an Eco-Friendly Head Impact Protection Device
## 1 Introduction

Table 2: Frequency, distribution, and rates of select injuries for games and practices combined for 15 sports, 1988–1989 to 2003–2004 [14]. From Table 3, it becomes clear that most impacts occur at the forehead (44.7%), followed by the lateral (22.3%), back (5.7%), and top (5.5%) impacts. An additional 551 concussions (21.8%) had an unknown impact location. The highest rate of concussions resulting from player-to-player collisions was in competition [23]. In this sense, the use of a headband improves dramatically the possibilities of protecting an injury site in case of sports that traditionally do not have head protection devices (e.g., soccer, field hockey). In fact, headbands are an excellent alternative to classic helmets that could be used in sports where head protection is not required/mandatory and where a helmet would certainly decrease the players' performance. Commercial headbands cover around 50%-55% of the head being made of synthetic cellular materials with the objective to reduce impact force. Under compressive strains, cellular materials are able to undergo very large strains keeping an almost constant and relatively low-stress level (the so-called plateau) until the material gets completely packed (densification stage). Such features allow them to absorb large amounts of energy [24]. Following the United Nation's 2030 agenda of the sustainable development goals, there is significant pressure on the producers to provide sustainable and eco-friendly alternatives to the current market solutions. Cork is mainly a visco-elastic cellular material, being capable to absorb considerable amounts of deformation energy. The initial undeformed shape is practically entirely recovered after unloading, a desirable feature regarding multi-impact scenarios [24; 25]. In addition, for cork agglomerates, it is perfectly possible to tune its mechanical properties, by changing density or binder type [26; 27]. These features make cork an ideal substitute for synthetic cellular materials [25; 28]. \begin{table}
\begin{tabular}{l l l l l l} \hline \hline \multicolumn{1}{c}{**School Year**} & \multicolumn{3}{c}{**Impact Location**} & \multicolumn{1}{c}{**Total**} \\ \hline  & **Back** & **Front** & **Side** & **Top** & **Unknown b ** & \\ \hline
**2008/2009** & & & & & & \\ n(\%) & 21 (5.9) & 146 (41.0) & 68 (19.1) & 21 (5.9) & 100 (28.1) & 365(100) \\ Rate & 0.4 & 2.5 & 1.2 & 0.4 & 1.7 & 6.1 \\ (95\% CI) & (0.2–0.5) & (2.1–2.9) & (0.9–1.4) & (0.2–0.5) & (1.4–2.0) & (5.4–6.7) \\ \hline
**2009/2010** & & & & & & \\ n (\%) & 22 (4.9) & 189 (42.5) & 106 (23.8) & 29 (6.5) & 99 (22.3) & 445 (100) \\ Rate & 0.5 & 4.0 & 2.2 & 0.6 & 2.1 & 7.5 \\ (95\% CI) & (0.3–0.7) & (3.4–4.5) & (1.8–2.7) & (0.4–0.8) & (1.7–2.5) & (6.7–8.3) \\ \hline
**2010/2011** & & & & & & \\ n (\%) & 35 (7.5) & 219 (47.0) & 97 (20.8) & 19 (4.1) & 96 (20.6) & 466 (100) \\ Rate & 0.7 & 4.6 & 2.0 & 0.4 & 2.0 & 7.5 \\ (95\% CI) & (0.5–1.0) & (4.0–5.2) & (1.6–2.5) & (0.2–0.6) & (1.6–2.4) & (6.7–8.3) \\ \hline
**2011/2012** & & & & & & \\ n (\%) & 26 (5.1) & 235 (46.3) & 114 (22.4) & 33 (6.5) & 100 (19.7) & 508 (100) \\ Rate & 0.6 & 5.0 & 2.4 & 0.7 & 2.1 & 8.4 \\ (95\% CI) & (0.3–0.8) & (4.4–5.6) & (2.0–2.9) & (0.5–0.9) & (1.7–2.5) & (7.6–9.2) \\ \hline
**2012/2013** & & & & & & \\ n (\%) & 39 (5.2) & 341 (45.4) & 179 (23.8) & 36 (4.8) & 156 (20.8) & 751 (100) \\ Rate & 0.8 & 6.7 & 3.5 & 0.7 & 3.1 & 9.2 \\ (95\% CI) & (0.5–1.0) & (6.0–7.4) & (3.0–4.0) & (0.5–0.9) & (2.6–3.5) & (8.3–10.1) \\ \hline
**Total** & & & & & \\ n (\%) & 143 (5.7) & 1130 (44.7) & 564 (22.3) & 138 (5.5) & 551 (21.8) & 2526 (100) \\ Rate & 0.6 & 4.5 & 2.2 & 0.5 & 2.2 & 10.0 \\ (95\% CI) & (0.5–0.7) & (4.2–4.8) & (2.1–2.4) & (0.5–0.6) & (2.0–2.4) & (9.6–10.4) \\ \hline \hline \end{tabular}  
*: Rates per 10,000 Athletic Exposures (AEs). b: Athlete stated not knowing impact location, or athlete did not reported impact location.  
\end{table} 
Table 3: Annual concussion data a (and 95% CIs), for American football players, regarding different school years and impact location [23].