Question on muscles used in the 40?

[WCUfballer]

Which muscle is more important in achieving low times in 40 yd dash or 100 meter dash ect....should I focus more on calves, hams, or thighs???And what are some good exercises in the weight room that would help me develop these muscles in order to in the long run achieve a goal of 4.5 in the forty????

Hams and Calves.

Taken from that previously cited Ken Mannie article:

Building a Strong Engine
An all-inclusive strength-training program is a requisite to speed improvement. Progressive strength-training results in more muscle force production, which translates into more powerful running strides. Running is a total body activity; thus it requires a total body strength-training program. The routines we've described in past articles will fit the bill.

The low back, abdominals, hips, and legs deserve special mention. These musculo-tendinous compartments perform the brunt of the work, or, at the very least, stabilize the body in maintaining the proper running mechanics. In effect, they are the machinery of a strong sprint engine. All coaches should have at least a general background in the muscular structures comprising these areas and their target exercises:

Low Back: The erector spinae group (spinalis, longissimus, and iliocostalis), the transversospinalis group (multifidi, rotatores, and semispinalis), and the quadratus lumborum, are important muscles in this area. Collectively, these structures are responsible for extending, laterally flexing, and rotating the vertebral column, as well as extending the hip. Exercises such as low back extensions, side bends, trunk rotations, and hip extensions, should be performed on a regular basis.

Abdominals: The four abdominal muscles (rectus abdominus, external oblique, internal oblique, and transverse abdominus) perform the functions of flexing the thorax, as well as rotating and laterally flexing the vertebral column. These muscles are critical in trunk stabilization when running. We perform a series of abdominal exercises through varying ranges of motion with body weight, machines, and/or or medicine balls at least twice per week.

Hips: The anterior flexors of the hip (psoas major and iliacus) are crucial in leg lift and drive. The gluteals (maximus, medius, and minimus) and the "deep six" muscles of the hip (piriformis, quadratus femoris, obturator internus, obturator externus, gemellus superior, and gemellus inferior) serve to flex, extend, abduct, adduct, and medially or laterally rotate the hip. For these complexes, we perform single-joint and multi-joint movements including hip flexion, hip extension, abduction/adduction, leg presses, dead lifts, lunges, and squats.

Thighs: The anterior thigh is composed of the quadriceps group (rectus femoris,vastus medialis, vastus lateralis, and vastus intermedius), which extend the knee (rectus femoris also flexes the hip). The posterior thigh houses the hamstring group (semitendinosus, semimembranosus, and biceps femoris), which flex the knee, extend the hip, and tilt the pelvis posteriorly. They also laterally and medially rotate the hip. Along with the multi-joint movements mentioned for the hip, we also isolate these compartments with leg extensions (quadriceps) and leg curls (hamstrings). The adductor group (adductor magnus, adductor longus, adductor brevis, pectineus, and gracilis) is located on the medial thigh, and is responsible for adducting and medially rotating the thigh. The tensor fascia latae and the iliotibial tract are located on the lateral thigh and they medially rotate and abduct the hip. To cover these areas, we perform adduction (inner thigh) and abduction (outer thigh/hip) movements with machines, stretch cords, or manual resistance. Another important muscle is the sartorious -- the longest muscle in the body * and it stretches from the anterior hip to the medial aspect of the knee. It flexes, laterally rotates, and abducts the hip. It can be strengthened with the aforementioned exercises for hip flexion and abduction.