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robbenisme
03-02-10, 11:42 PM
To give an example of muscle strength, a world-class weight lifter might have a quadriceps muscle with a cross-sectional area as great as 150 square centimeters. This would translate into a maximal contractile strength of 525 kilograms (or 1155 pounds), with all this force applied to the patellar tendon. Therefore, one can readily understand how it is possible for this tendon at times to be ruptured or actually to be avulsed from its insertion into the tibia below the knee. Also, when such forces occur in tendons that span a joint, similar forces are applied to the surfaces of the joint or sometimes to ligaments spanning the joints, thus accounting for such happenings as displaced cartilages, compression fractures about the joint, and torn ligaments.
Sports physiology-the muscle in exercise-Strength, Power, and Endurance of Muscles

Còn đọan này nữa:
One of the cardinal principles of muscle development during athletic training is the following: Muscles that function under no load, even if they are exercised for hours on end, increase little in strength. At the other extreme, muscles that contract at more than 50 per cent maximal force of contraction will develop strength rapidly even if the contractions are performed only a few times each day. Using this principle, experiments on muscle building have shown that six nearly maximal muscle contractions performed in three sets 3 days a week give approximately optimal increase in muscle strength, without producing chronic muscle fatigue.
The upper curve in Figure 84-5 shows the approximate percentage increase in strength that can be achieved in a previously untrained young person by this resistive training program, demonstrating that the muscle strength increases about 30 per cent during the first 6 to 8 weeks but almost plateaus after that time. Along with this increase in strength is an approximately equal percentage increase in muscle mass, which is called muscle hypertrophy.
In old age, many people become so sedentary that their muscles atrophy tremendously. In these instances, muscle training often increases muscle strength more than 100 per cent.
Sports physiology- The Muscles in exercise - Effect of athletic training on muscles and muscle performance
Cám ơn các anh chị rất nhiều.

taoyk32
04-02-10, 10:16 AM
Đoạn 1: giải thích bằng trả lời 2 câu hỏi:
1. Sức cơ phụ thuộc yếu tố nào?
2. Khi co 1 cơ, lực sinh ra sẽ tác động lên đâu?
Đoạn 2: cách tập luyện cơ cho hiệu quả, chứ không biết giải thích làm sao...
Xem hình:
http://www.eorthopod.com/images/ContentImages/knee/knee_quadriceps_tendonitis/knee_tendonitis_quadriceps_anatomy02.jpg
Khi quadricep co:
http://saveyourself.ca/resources/images/quads-diagram.gif