The hamstring is not merely one muscle. It is a group of 3 muscles that run down the back of the leg. The muscles include the semimembranosus, the semitendinosus, and the biceps femoris. These muscles bend the leg at the knee and also move the extend the leg at the hip joint. They are especially important for power in sprinting. The forces that result from speedwork or sprinting often cause injury to this muscle group. The increased use in sprinting causes a higher incidence of hamstring "pulls" in sports in which sprinting is required. This includes track and field, baseball (running and sprinting with inadequate warmup or after a cool down period even after a good warmup), basketball, soccer, football, and even from speedwork or sprinting up hills in long distance runners supplementing and diversifying their training.

What Is A Hamstring Pull

A hamstring pull is a type of "muscle strain". This is the muscle equivalent of a ligament sprain. Muscle fibers are torn either partially or completely. A crude three point grading system is used ranging from microtears and partial tear to a complete tear of the muscle. Sometimes an avulsion of the muscle may occur at the origin. CT scans and MRI may be used to define the more serious injuries.

Anatomy:

Semimembranosus

Origin: Upper and lateral portion of ischial tuberosity.

Insertion: Medial tibial condyle - groove. Into oblique posterior capsular
ligament. Fascia covering the popliteus muscle.

Innervation: Sciatic Nerve

Semitendinosus

Origin: From common tendon with long head of biceps at the ischial tuberosity.

Insertion: Medial surface of tibia, just below the insertion of the sartorius and gracilis muscles.

Innervation: Function:

Biceps Femoris

Origin:
Long head: From a common tendon with the semitendinosus muscle and from the upper and medial portion of the ischial tuberosity.

Short head: From the linea aspera and lateral portion of the lateral supracondylar line.

Insertion: Head of the fibula.

Innervation: Sciatic Nerve

Group functions: These are all two joint muscles - hip and knee. Extension at the hip, flexion at the knee. Minor functions are rotary in nature. The semimembranosus and semitendinosus will externally rotate the tibia when the hip is extended and will internally rotate the tibia when the hip is flexed. In the sprinting gait, the eccentric contraction in the latter phases of open chain gait is a likely factor in the injury of this muscle group. Recent publications support this theory (Bing et. al. 2008). The hamstring muscles generated the largest forces during the early stance phase and the late swing phase. During the late swing phase the forces were two to three times greater than during the late stance phase and the early swing phase.

Bing et. al. (2008) concluded the following:

The muscle–tendon length, which in effect is a condition of "strain" and likely related to injury, was found to be, at the peak elongation velocity, significantly greater also during the late stance phase compared with the late swing phase. The semimembranosus muscle–tendon length at peak elongation velocity during the same phase, the late stance phase, was found to be significantly greater than the biceps femoris and semitendinosus. There was no significant difference in the muscle–tendon length at the peak elongation velocity during the late swing phase. However, the peak muscle–tendon length of the biceps femoris and semitendinosus were significantly greater during the late swing phase than during the late stance phase. While the peak muscle–tendon length of the semimembranosus was significantly longer than those of the biceps femoris and semitendinosus during the late stance phase. No significant difference existed in the peak muscle–tendon length among muscles during the late swing phase (p=0.156)

Although both the late stance and early swing phases have increased forces and strain potential, the two phases of gait during which injury may occur might predispose to different injury locations. Bing et. al. (2008) noted that in previous studies such as Best et al. (1995) demonstrated that strain injury occurred at the muscle–tendon junction when the strain rate was low while occurring at the the distal muscle belly in cases of high strain rate. was high. Bing et. al. (2008) demonstrated that that the hamstring muscle elongation velocity was significantly higher during the late stance phase than during the late swing phase. Their conclusion was that in combination with Best et al. (1995) was that a strain injury may be more likely to occur "at the hamstring muscle–tendon junction during the late stance phase than during the late swing phase while it may be more likely to occur at the muscle belly during the late swing phase than during the late stance phase."

What Causes A Hamsting Pull?

Hamstring pulls occur often in many sports that involve sprinting. One of the primary reasons for a hamstring pull to occur is relative inflexibility in this area. This injury might not be caused by weak hamstrings, but rather in hamstrings that were originally of adequate strength but the athlete had not worked on their flexibility. Frequently there is a muscle strength imbalance. Burkett reported in 1970 that hamstrings were more prone to injury when they were less than 60% as strong as the Quadriceps. There are many other knee injuries that occur though when the quadriceps are weaker than they should be. This is of particular importance in reference to the vastus medialis, which must be of adequate strength to insure proper tracking of the patella. While extremely weak hamstrings may contribute to problems, it is possible that the weakness may occur following a previously unknown minor injury. Whenever the hamstring muscle group becomes injured, the strength of this group has been found to be will be weaker than normal in eccentric contraction. A valid debate is whether the injury occurs in the presence of weakness in which many poorly trained fibers are recruited to create a stronger contraction and in which case these fibers are injured or in a strong contraction in which the fibers are not appropriately prepared by a proper warmup and conditioning program (flexibility and strength training). While Best, in his excellent review article, cited a study of a small sample group that claimed to predict hamstring injury based on strength, he also came to the conclusion that this might not be a readily predictable injury.

Fatigue may also be a factor in this injury. A program involving stretching at oppportune moments throughout the time in which a sport is undertaken has been used in lowering the injury rate in soccer players and Australian rules football. (Verrall et. al. 2005).

 

Training Cycles Aerobic Base/Endurance Hills/Strength/Transition Stamina Aerobic Capacity and Anaerobic Tolerance Peak Racing Graduate the stresses within one cycle and while transitioning to the next. Give yourself recovery time between hard workouts. Don't forget to get enough sleep.

Transitioning And Building In Your Training   There are many coaches with theories to offer on training cycles. Most will recommend a modification and modernization of Arthur Lydiard's recommendations from years ago. The progression is to build up distance for a strong aerobic base, transition to harder and faster workouts and then perform high quality speed workouts before reaching peak racing season. This allows for a gradual introduction of speedwork after your aerobic base has been built and after you have worked in a gradually building amount of fartlek, hills, and lactate threshold runs into your program during the transition phase. By using phases in your training you will let your muscles gradually adapt to the stresses you are going to placing them under. Your hamstrings will become accustomed to the longer stride you will use in your speedwork and faster running. Gradual adaptation will lessen the chances of an injury. A phased approach to your training will help give your body a chance to adapt to the new and more difficult stresses you are throwing its way. All athletes performing speed work must work hard on their flexibility, have a proper warm up before training, a proper staging of training cycles, and adequate strength conditioning along with proper muscle balance. I've listed flexibility first because that is most often neglected. The warm up is vital because without a thorough warm up you are prone to "pulling" your hamstrings. For those competing at distances longer than 1 mile there is no need to "jump" into your sprints when doing speed work. Ease into faster running with a gradual speedup. You don't need to practice your "starts" and "pull" your muscles in the process.

 

Differential Diagnosis: Sciatica, herniated disk, and other clinical entities may mascarade as an injured hamstring. If your injury does not respond to rest within 10 days, you should visit a sports medicine physician. Physical examination will usually reveal the nature and location of the injury.

Stride Length & Hamstring Injuries

A longer stride length helps running economy for faster running. Many long distance runners train too slow for long periods of time and develop an abnormally short stride. When it comes time for speedwork in your marathon or half marathon training plan, you will have to gradually increase your stride length. Be on the safe side and increase your leg turn over rate, rather than
just increasing your stride length. Unless you warm up carefully and try to gradually transition to speed work, you are at risk for a hamstring injury. If you have already developed a "pulled hamstring", you will have to decrease your stride length until the muscle is completely healed.

Treatment:

For an acute injury ice and anti-inflammatory medication is helpful. Later rest and gentle compression may also be used. In rehabilitation rest is important followed by very gentle stretching and then gentle strengthening before any more vigorous therapy is undertaken. Hard speedwork must be eliminated until the muscle has recovered. Care must be taken to avoid
reinjury of the muscle. In running you will need to shorten your stride. In the future you will need to warm up exceedingly carefully before doing any speedwork. It may take 1/2 hour or longer to do a proper warmup:

• Run 2 miles at a glacial pace
• Stretch gently
• High knees
• Strides
• Stretch again
• Ease into your speedwork. Don't practice quick and explosive starts.
• When you've completed your speedwork. Warm down by running slowly for 1 to 2 miles and then stretch gently.

You may consider using ice after a workout and moist heat before. This is used by many individuals. Overuse of heat will cause swelling and over use of ice, besides injuring the skin, may limit the circulation to the area which is needed to flush out waste products and bring in nutrients. It does act as a short term anti-inflammatory and also lessens pain.

Prevention:

Studies of other muscle groups and a study by Worell showed that flexibility and strength training result in improved performance of the hamstring muscle group. So besides helping prevent an injury, stretching and strength training may enhance your performance. While we may not have research that precisely shows us who is prone to this injury, clinical experience gives us the guidelines we've discussed.

• Strength Conditioning Program
• Flexibility Program and the use of stretching at opportune moments during sport
• Phased Approach To Training
• Gentle Warmup First By Running, Stretching, High Knees, Strides, Stretch Again

 

Warming Up: Effects Raises core body temperature Increases elasticity Prepares your nervous system for work Improves muscle contractility Prepares cardiovascular system for a workout Improves coordination Increases awareness, arousal and improves reaction time Increases work capacity

The Warm Up A warm up is considered vital for all performing speedwork. The more speedwork is a part of your routine, or if short distance events are your main event, you know how long it takes and how important it is to warm up properly. Warming up is a process. It is a series of things that are done to prepare your body for the stresses of training or competing. Your warm up should include 15 to 20 minutes of slow running. Run 2 miles at a glacial pace Stretch gently High knees Strides Stretch again Ease into your speedwork. Don't practice quick and explosive starts. When you've completed your speedwork. Warm down by running slowly for 1 to 2 miles and then stretch gently. You should never do intervals or sprint without a thorough warm up. If you are a long distance runner why not give your fast twitch fibers a chance to get ready to be put through the paces.

References:

Best, TM, Garrett, WE, Physician and Sports Medicine VOL 24 - NO. 8 August 1996

Best, T.M., McElhaney, J.H., Garrett Jr, W.E.. and Myers, B.S. . Axial strain measurements in skeletal muscle at various strain rates, Journal of Biomechanical Engineering 117 (1995), pp. 262–265.

Bing Yu, Robin M. Queen, Alicia N. Abbey, Yu Liu, Claude T. Moorman, William E. Garrett, Hamstring muscle kinematics and activation during overground sprinting, Journal of Biomechanics, Volume 41, Issue 15, 14 November 2008, Pages 3121-3126, ISSN 0021-9290, DOI: 10.1016/j.jbiomech.2008.09.005.
(http://www.sciencedirect.com/science/article/B6T82-4TMYK1D-3/2/5afe63d167062eb0aec1b760ca57aee6)

Burkett LN: Causative factors of hamstring strains. Med Sci Sports Exercise 1970;2(1):39-42

Jonhagen S, Nemeth G, Eriksson E: Hamstring injuries in sprinters: the role of concentric
and eccentric hamstring muscle strength and flexibility. Am J Sports Med 1994;22(2):262-266

Thelen, D; Chumanov, E; Hoerth, D.; Best, T.; Swanson, S.; LI,L; Young, .M; Heiderscheit, B." Hamstring Muscle Kinematics during Treadmill Sprinting". Medicine & Science in Sports & Exercise. 37(1):108-114, January 2005.

Verrall, G; Slavotinek, J; Barnes, P: The effect of sports specific training on reducing the incidence of hamstring injuries in professional Australian Rules football players. BJSM 2005, 39(6): 363-368

Wood, G.A. Biomechanical limitations to sprint running, Medicine and Sport Science 25 (1987), pp. 58–71.

Worrell TW, Smith TL, Winegardner J: Effect of hamstring stretching on hamstring muscle
performance. J Orthop Sports Phys Ther 1994;20(3):154-159