So sánh phương pháp

	Tốc độ phát triển lực	Chỉ số Sức mạnh Phản xạ
Lĩnh vực	Khoa học thể thao	Khoa học thể thao
Họ	Hypothesis test	Hypothesis test
Năm ra đời	2002	1987
Người khởi xướng	Peter Aagaard	Marteen Bobbert
Loại	isometric force measurement	elastic response test
Công trình gốc	Aagaard, P., Simonsen, E. B., Andersen, J. L., Magnusson, P., & Dyhre-Poulsen, P. (2002). Increased rate of force development and neural drive of human skeletal muscle following resistance training. Journal of Applied Physiology, 93(3), 1318-1326.	Bobbert, M. F., Huijing, P. A., & van Ingen Schenau, G. J. (1987). Drop jumping. II. The influence of dropping height on the biomechanics of takeoff after landing. Medicine & Science in Sports & Exercise, 19(4), 339-346.
Tên gọi khác	RFD, explosive strength, force development rate, strength impulse	RSI, stretch-shortening cycle, elastic response
Liên quan	5	3
Tóm tắt	Rate of force development (RFD) is the speed at which force is produced during the initial phase of muscle contraction, typically expressed as the slope of the force-time curve in the first 50, 100, or 200 milliseconds of isometric contraction. Introduced comprehensively by Aagaard and colleagues (2002), RFD is a measure of explosive strength capacity and neural drive efficiency. Unlike maximal voluntary strength (which captures peak force), RFD captures how quickly an athlete can generate that force—a critical quality in sports requiring rapid, explosive movements (sprinting starts, jumping, tackling). RFD improves dramatically with strength training, reflecting increased motor unit recruitment rate and firing frequency.	The reactive strength index (RSI) is a measure of lower-body reactive strength and elastic energy utilization, calculated as jump height divided by the contact time between landing from a drop and takeoff. Introduced by Bobbert and colleagues (1987), RSI quantifies the efficiency of the stretch-shortening cycle (SSC)—the ability to rapidly switch from eccentric (lengthening) to concentric (shortening) muscle contractions. High RSI indicates rapid, forceful engagement of muscles' elastic properties (tendons, contractile proteins) and is relevant in sports requiring rapid rebound (sprinting, jumping, rebounding). RSI is trainable and sensitive to plyometric training.