Participation in physical activity has an important role in a healthy lifestyle. However, it is associated with an inherent risk of injury. A lateral ankle sprains (LAS) is the most prevalent lower extremity injury in sports and everyday life, posing a substantial healthcare burden and resulting in many long-term complications. Despite the attention and focus ankle sprains receive, it has been reported that up to 74% of individuals who experience an ankle sprain suffer from some type of residual symptoms, perceived instability (repeated episodes of “giving-way”), recurrent ankle sprains, and/or self-assessed disability, which may be termed as chronic ankle instability (CAI). The presence of CAI decreases activity levels, limits occupational involvements, and adversely impacts quality of life, as well as develops an early onset of degenerative pathology in the ankle, requiring costly medical diagnostic techniques and extensive treatments. Therefore, CAI is a significant public health concern in the physically active population and an economic burden of the global health care systems. With increasing government and societal emphasis on physical activity, the incidence of CAI would remain constant or increase as more individuals participate in physical activities. Researchers and clinicians must work together to minimize complications of CAI to maximize the potential health benefits of a physically active lifestyle.

Although ankle sprains receive abundant attention and focus in clinical practice and research, they persist as the most common injury that leads to recurrent injury in athletic activities. Understanding the cause of recurrent injury is crucial in implementing therapeutic interventions to ankle injury and reducing recurrent injury rate. Although excessive plantar flexion with inversion and external rotation in the ankle has been believed as the mechanism of an ankle sprain, it appears that the ankle sprain injury mechanism excessive rearfoot inversion and internal rotation coupled with ankle dorsiflexion. While various studies have shown that there are feed-forward and feedback alterations present in individuals with chronic ankle instability (CAI) as manifesting altered movement organization and muscle activation patterns during functional tasks, it is unclear whether these alterations are the result of the injury or initially contributed to it due to the lack of prospective studies. It is possible that compromised feedback responses, which may have been caused by the initial ankle sprain, contribute to the altered feed-forward control. Ankle instability appears to be linked to multiple aspects of insufficiencies. However, the potential synergistic relation between mechanical and sensorimotor impairments associated with CAI are unclear. It is important for future investigations to identify the source of alterations associated with CAI and identify exact factors that cause recurrent and secondary injury for developing more effective intervention and injury prediction model. Interventions that address multi-factorial aspects of impairments associated with CAI also are essential for improving both patient-oriented and clinician-oriented functional measures, decreasing disability, and preserving long-term healthy in individuals with CAI.

Lateral ankle sprain (LAS) is one of the most common injuries in competitive sports. This article organized the scientific evidence about the pathology, evaluation and treatment of LAS and chronic ankle instability (CAI). Athletes who injured LAS has various symptoms such as inflammation, restriction of joint range of motion, muscle strength deficit, decline balance control, fundamental movement abnormality which caused by various tissue damage. For LAS, it is important to properly evaluate these dysfunctions and advance treatment under the control of the athletic trainer, thereby preventing recurrent sprains and progression to CAI. In treatment for CAI, it is important to properly evaluate mechanical instability, functional instability, perceived instability, and functional performance and to organize individual disease states. Although treatments of CAI are verified by various methods such as balance exercise, joint mobilization, soft tissue mobilization, and resistance training, balance training is considered to be advantageous to prevent of recurrent sprains and improvement of activity of daily living. In future, it is necessary to develop appropriate treatment protocols according to severity and pathological condition.

Sports-related ankle sprains are extremely common among physically active population. An acute lateral ankle sprain typically causes pain, swelling, tenderness, and instability at the joint. The previous history of at least one ankle sprain has been identified as the strongest predictor of recurrent ankle sprains. It has been reported that the recurrent rate of ankle sprains exceeds 70%. Early injury management and proper follow-up care can help the healing process and reduce the risk of recurrent ankle sprains. In spite of these facts, many individuals who have suffered with ankle sprains do not seek medical treatment from a health care provider. Unfortunately, after the first ankle sprain, many individuals experience recurrent ankle sprains and suffer residual symptoms. Experiencing repetitive ankle sprains cause alteration in ankle joint mechanics and functions due to repeated disruptions in the structural integrity of the ankle, and it can lead to long-term consequences such as decreased health related quality of life and physical activity level throughout their lifetime. Furthermore, it has been reported that repetitive ankle sprains increase the risk of developing early onset post-traumatic osteoarthritis at the ankle. This evidence-based review explains overview of sports-related ankle sprain, residual symptoms associated with ankle sprains, and prevention of recurrent ankle sprains.

本研究は，足関節筋腱スティフネスの違いがストレッチング効果に与える影響を検証した．健常男子大学生12名の足関節底屈筋に対して2分間のストレッチングを行い，その前後の足関節最大背屈ROM，筋腱スティフネスを調べ，関係性を検討した．結果，ストレッチング前後で有意なROM増加と筋腱スティフネス低下を認めた（p<0.01）．また，ストレッチング前の筋腱スティフネスとROM増加率において有意な負の相関関係が示された（r＝−0.69，P＝0.011）ことから，筋腱スティフネスの違いはストレッチング効果に影響を及ぼし，筋腱スティフネスが高値ほど柔軟性改善効果は小さくなることが示唆された．

高校年代の野球選手において投球過多が問題となっている．本研究では投球をおこなう間隔日数（登板間隔）に着目し，異なる登板間隔で投球課題を実施することによって，投球パフォーマンスにどのような影響を及ぼすのかについて比較検討した．その結果，身体機能および投球フォームについてはいずれの条件においても有意差は示されなかったが，球速についてはいずれの条件でも球速低下は生じたものの，中2日での登板は連投および中1日での登板に比べて有意に球速の低下を抑えることができた．以上の結果より投球パフォーマンス維持の効果が発揮され始めるためには，登板後少なくとも2日以上の休息日を設けることが必要であることが示唆された．

本研究では，足関節のテーピングによる固定と局所疲労課題がバウンディングパフォーマンスと下肢関節の挙動に与える影響を検討した．12名の大学生アスリートを対象に2歩のバウンディングジャンプを行わせ，最初に踏み出す足を分析足として跳躍距離，接地時間，足・膝・股関節角度，骨盤の挙動，地面反力，筋電図を測定した．一元配置分散分析を用いて，コントロール条件，テーピング条件，足関節底屈筋疲労条件の3条件で比較した．その結果，テーピング条件と足関節底屈筋疲労条件でバウンディングの跳躍距離は低下し，下肢関節の代償動作が確認された．ジャンプパフォーマンスにとって足関節の可動性と筋機能を確保することは重要であることが示唆された．

方向転換動作時の動作方向と足底圧分布の関係を調査することを目的に研究を行った．サッカー選手18名を対象とし，サイドカッティング動作，クロスオーバーステップ動作，直線のランニングの3つの動作時の足底圧を計測した．サイドカッティング方向の動作において前足部内側の最大接触圧が有意に大きく（589kPa vs 318kPa，414kPa，p<0.05），クロスオーバー方向への動作では，外側中足部・前足部の最大接触圧が有意に大きい値（362kPa vs 255kPa, 275kPa，p<0.05）を示した．このことから，方向転換動作時は進行方向側の中足部・前足部のストレスが増大することが示唆された．今後は，方向転換の動作方向と傷害との関連も調査していく必要がある．