重複試驗之疲勞因子對犬隻測力板垂直反作用力數據之影響

Abstract

測力板（force plate）為一項靈敏且準確的客觀儀器，可即時量測出動物運動時，肢體地面反作用力之變化，故為許多臨床手術以及藥物效果實驗所採用。然而，許多因素都可能會影響地面反作用力的表現，進而造成測力板數值之變異。包括：品種、體重、步態、病理變化、行進速率、不同受試日（interday variance）、不同次試驗（intertrial variance）、起跑距離…等。研究者進行相關實驗時，須審慎評估並減少上述因子之影響。 測力板雖為獸醫界所採用，但受限於動物無法準確遵循人類指令，故為收集到足夠分析的數據量，重複性試驗為此類研究所無法避免的狀況。然而，多次的試驗可能使動物疲憊，繼而影響地面反作用力的表現，為瞭解試驗次數之疲勞因子（fatigue factor）與地面反作用力間的相關性，故進行本研究。 共九隻健康犬隻以及九隻自然發生後肢輕度跛行的犬隻參與本研究。所有動物皆於一天內，由同一引領者下進行一百次的連續試驗。引領者帶領受試犬隻以急行（trotting）步態通過測力板系統，受試犬之行進速率則依體型略作調整，僅取速率差異在±０．２ ｍ�ｓ內的試驗數據納入有效數據。在收集前/後肢之最高垂直負重（peak vertical force）與垂直衝量（vertical impulse）數據後，以Levene’s同質性檢定與混合式重複試驗回歸模型（mixed regression model for repeated measurement data）進行統計分析。 結論發現不論是健康犬或異常犬的各測力板參數皆未顯示顯著變異，顯示在１００次重複測試中，疲勞因子對研究犬的地面反作用力影響甚微。 由本結果得知，在１００次測試之內，健康與輕微後肢跛行犬隻的垂直向地面反作用力並不會出現顯著差異，於研究時，只要動物沒有不願意或無法進行急行行進的情況，且測試總次量控制在１００次之內時，可以忽略疲勞因素在多次重複測試所造成之誤差。

Force plate is a sensitive, accurate, and objective equipment which simultaneously display the changes of ground reaction forces during animal’s locomotion. It is widely applied in the evaluation of surgical outcomes and pharmaceutical effects. However, literatures have indicated many factors including breed, body weight, gait, pathologic changes, subject velocity, interday variance, intertrial variance, and starting distance could all contribute to the variables of force plate measurement. Researchers must carefully evaluation those factors in order to avoid unwanted bias. Although force plate has becoming more popular in veterinary studies, due to the difficulty in patient control, numerous repetitions are often required to acquire valid data. According to a previous research, most dogs requires 45.3±4.7 and 57.8±6.0 trials to achieve 5 valid trials in walking and trotting gait. However, fatigue caused by repetitive trials may lead to variations in the measured ground reaction forces. The purpose of this study is to investigate the relationships between multiple trial repetitions and magnitude of the ground reaction forces. A total of 9 healthy dogs (healthy group) and 9 dogs with natural occurring hindlimbs lameness (abnormal group) were included in the study. One hundred repeated trials were performed on each animal by the same handler in each session, the participants were maintained at a stable trotting gait while crossing the force plate system. Dogs were allowed to trot at their preferred speed, however only data obtained within±0.2 m/s were used for analysis. Peak vertical force (PVF) and vertical impulse (VI) of forelimbs and hindlimbs were collected. The collected data in each 100 trials were further divided into 4 distinct blocks, each containing 25 trials. Levene’s test for homogeneity and mixed regression model for repeated measurements were used to test the differences between blocks on each categories with the statistical significance level set at 5% (α = 0.05). According to the study, both the peak vertical force and vertical impulse remain consistent within a session of 100 repetitive trials in healthy and dogs with mild lameness. It is suggested that the fatigue factor under this condition affects minimally to the vertical ground reaction forces and could be ignored.