緒論：阻力訓練是青少年運動員競技潛能發展的策略，若有良好的訓練計畫並予以監控，可避免傷害的發生並促進身心發展。本研究的目的是評估自由式及機械式阻力訓練對青少年運動員肌肉質量及運動表現之增強效果。方法： 26名男性青少年運動員隨機分配為自由式阻力訓練組 (背蹲舉訓練 ) 及機械式阻力訓練組 (下肢推蹬訓練 )，進行十週每週 3次的週期化訓練課程，並於訓練前及每一訓練週期結束後實施肌肉質量及運動表現 (最大肌力、爆發力、速度及敏捷 ) 檢測。所得數據以單因子重複量數及獨立樣本 t考驗，比較二組各項指標之組內與組間差異。結果：二組於週期化訓練期間之肌肉質量及運動表現均呈現增長且各依變項最高增長期也相同；肌肉質量最高增長期發生在肌耐力訓練期、最大肌力最高增長期發生在最大肌力訓練期、爆發力最高增長期及速度最高增長期均發生在速度與爆發力訓練期，敏捷最高增長期發生在最大肌力訓練期。二組經過十週訓練後，肌肉質量與運動表現均獲得顯著增強效果。自由式阻力訓練組爆發力 (反向跳) 增強百分比顯著高於機械式阻力訓練組 (4.68% 與 2.15%)。結論：青少年運動員以週期化進行自由式阻力訓練及機械式阻力訓練後，肌肉質量及運動表現均呈現增長並獲得顯著增強效果。此外，本研究發現，相較於機械式阻力訓練，自由式阻力訓練是發展爆發力較為優勢的訓練法。

Introduction: A properly designed and supervised resistance training is not only enhance the muscular strength and power of youth, but also improve motor skill performance and may contribute to enhance sports performance of youth. However, what kind of resistance training method can have better training efficiency for young athletes is an important research topic. The aim of this study was to compare 10 weeks of free-weight training and machine-based training on young athletes’ muscle mass and exercise performance. Methods: 26 male young athletes were randomly divided into free-weight training group (back squat training) and machine-based training group (leg press training). Two experimental groups completed a 10 week resistance training program that included 3 training sessions per week. Before and after the each training period, the percentage of muscle mass, the 1-repetition-maximum in the back squat and the leg press, the countermovement jump, the 15 meters sprint and T type shuttle running were evaluated. Data were analyzed by using repeated measured ANOVA and LSD post-hoc tests to compare difference within groups. T-test was used to compare the difference of training effects between groups. Results: The muscle mass and exercise performance of the two groups were increased during training period and the highest growth period of muscle mass and exercise performance were also the same. Both training group had significant training effects on muscle mass and exercise performance after resistance training. Free-weight training group’ explosive training effect (CMJ) was significant higher than machine-based training group (4.68% and 2.15%, respectively). Conclusion: Young athletes can use resistance training to enhance muscle mass and sport performance, not limited to free-weight resistance training or machine-based resistance training. Difference between two training groups was detected for the countermovement jump. In comparison with machine-based resistance training, free-weight resistance training might be a better strength training exercise for the development of explosive performance.