目的：本研究以自我決定理論與計畫行為理論為基礎，探究自行車極限挑戰活動參與者行為之影響因素及各變項間因果關係。方法：本研究以自行車騎乘里程數一天至少達200公里之自行車參與者為研究對象。研究工具為基本心理需求、計畫行為理論及其騎乘行為問卷。有效樣本共計463位，所得資料以路徑分析進行分析，檢視本研究模式適配度與影響效果，本研究使用IBM SPSS AMOS 22.0統計套裝軟體進行資料分析，並以.05作為統計顯著水準。結果：本研究之測量分析模式與實際資料整體適配度尚佳，自行車極限挑戰參與者之基本心理需求對態度、主觀規範與知覺行為控制存在顯著正向的影響；基本心理需求、態度、知覺行為控制對意圖有顯著正向的影響；知覺行為控制、意圖對行為有顯著正向的影響；最後，態度與知覺行為控制在基本心理需求與意圖間扮演中介角色。結論：自行車極限挑戰選手基本心理需求滿足可提昇意圖；正向積極態度、知覺行為控制，以及內、外在資源掌控程度愈高可增進行為涉入。建議考量提昇選手身、心理、技能之訓練策略，設置友善優質的訓練環境、設施以強化選手對於內、外在資源之掌控力。

Purpose: On the basis of the self-determination theory and theory of planned behavior, this study explored the factors influencing participant's behavior in extreme bicycle challenges as well as the relationships between these factors. Methods: Participants who engaged in extreme bicycle challenges and covered a minimum distance of 200 km per day were recruited. A questionnaire that focused on basic psychological needs, the theory of planned behavior, and cycling behavior was employed as the research instrument. In total, 463 valid samples were retrieved, and a path analysis of the collected data was conducted to assess the fit and effect of the research model. Data analysis was performed using the IBM SPSS Amos 22.0 statistical software, with the significance level set at .05. Results: The measurement analysis model exhibited a favorable overall fit with the actual data. The basic psychological needs of participants in extreme bicycle challenges had significant and positive effects on their attitude, subjective norms, and perceived behavioral control. Basic psychological needs, attitude, and perceived behavioral control had significant and positive effects on intention. In addition, perceived behavioral control and intention had significant and positive effects on behavior. Finally, attitude and perceived behavioral control mediated the relationship between basic psychological needs and intention. Conclusion: Meeting the basic psychological needs of extreme cycling athletes may enhance their intention to participate. A positive and proactive attitude, perceived behavioral control, and higher levels of internal and external resource control can promote behavioral involvement. Therefore, we recommend training strategies that enhance the physical, psychological, and skill-related dimensions of athletes; the establishment of a friendly and high-quality training environment; and the use of facilities that help athletes to strengthen their control over their internal and external resources.