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Predisposition to hamstring injury cannot be determined!

Proposition for Debate - by Lynne Thompson

Contents

• Statement of the Topic
• Introduction
• Background Knowledge
• Predisposing Factors
• Clinical Implications
• Summary
• Short Answer Review Questions
• References

Statement of the Topic

Predisposition to Hamstring Injury Cannot be Determined

Introduction

Hamstring injuries are the most common injuries in sports that involve sprinting, and jumping.

In Australian Rules football, hamstring injuries are the most frequent injuries, and account for the most playing time missed during a season.

Many predisposing factors have been put forward with regard to hamstring injuries, and the purpose of this paper is to investigate the literature to discover whether there is a common finding that can determine a population a risk.

Background Knowledge

Anatomy

The hamstring muscle group covers the posterior aspect of the thigh. It consists of three muscles, semitendinosis, semimembranosus, and biceps femoris. These muscles are comprised of mainly fast Type II muscle fibres (Garrett at al, 1989). The posterior portion of adductor magnus is often considered a part of this group due to its line of pull and shared origin with the hamstrings, however as it attaches to the adductor tubercle of the femur, it has no action on the knee joint.

In this group of muscles, biceps femoris is the most lateral of the group, and consists of two heads. The long head originates from the ischial tuberosity, shared with the other muscles, and sacrotuberous ligament, while the short head originates from the linea aspera on the posterior aspect of the femur. The two heads combine into a common tendon and insert into the head of the fibula and the lateral tibial condyle.

Each of the heads has a separate innervation. The tibial branch of the sciatic nerve (L5, S1-3) supplies the long head, and the peroneal branch (L5, S1, and S2) supplies the short head. The two heads should both produce flexion and lateral rotation of the knee, as well as tightening the posterolateral aspect of the knee. The long head also helps to produce lateral rotation, extension and adduction at the hip joint.

Semimembranosus and semitendinosis form the medial hamstrings. Semitendinosis shares its origin with the long head of biceps femoris at the ischial tuberosity, and forms a long tendon before inserting into anteromedial aspect of the tibia as part of the pes anserine group. Semimembranosus also arises from the ischial tuberosity and forms a thick tendon that inserts into the posteromedial aspect of the tibia. The tibial branch of the sciatic nerve innervates both of these muscles. These muscles produce flexion and medial rotation of the knee, and extension, medial rotation and adduction of the hip.

Biomechanics

Injuries to the hamstring muscles is most often seen in activities that require sprinting, either for short bursts of time or prolonged effort. It is necessary therefore to understand the role of the hamstring muscles in gait, especially in running.

In walking there are two phases of the gait cycle, stance and swing, and one limb is in contact with the ground at all times. However as speed increases, the length of the of the stance phase decreases, and there is a period of nonsupport time in which neither limb is in contact. With increases in running or sprinting speeds, the nonsupport phase increases, and the time in which the muscles have to work to produce this speed is shortened, making them have to contract faster and absorb force in a shorter period of time. (Worrell and Perrin, 1992).

During the initial swing phase, hamstring activity is quiet until the forward swing occurs where semimembranosus activates producing eccentric work to decelerate flexion of the thigh. Semimembranosus and semitendinosis increase in activity to reverse the thigh direction and decelerate the tibial extension, while the biceps femoris is quiet. The hamstring muscles become active in the last third of the swing phase, to control knee extension and in doing this they work eccentrically to decelerate the tibia and control hipflexion. Just before heel strike, the hamstrings work concentrically briefly to prepare for weight loading (Elliot and Blanksby 1979; Worrell and Perrin, 1992). At heel strike, semimembranosus and biceps femoris contract simultaneously to provide stability of the knee, with knee flexion also commencing. During the midsupport phase, semitendinosis fires to join with the other muscles to help with knee stability and hip extension. Prior to toe off when the heel has lifted, Elliot and Blankksby (1979), found that there was a spike in biceps femoris activity while the activity of the other muscles remained high. This high level of activity continued through as the knee flexed (Elliot and Blanksby, 1979).

Predisposing Factors

Many factors have been proposed as predisposing factors in hamstring injuries but there has been little, or conflicting, research into these. The following are a sample of those that have been put forward.

Hamstring Strength

Weakness of the hamstring muscles has long been debated as an aetiological factor in the injuries of the hamstring muscles.

For the argument of hamstring strength as a predisposing factor are Burkett 1970, Chistenson and Wiseman 1972, Heiser et al (1984); and Orchard et al (1997). Against are Lieholm 1978, Patton et al (1989); Worrell et al (1991); and Bennell et al (1998).

In the early studies if Burkett 1970, and Christenson and Wiseman 1972 were able to predict hamstring injuries in their study populations through hamstring strength and hamstring/quadrieps ratio. However these studies used small numbers (6 and 5 respectively) and therefore the percentages that they were able to predict are to be misrepresented.

Lieholm (1978) studied 27 athletes prospectively using hamstring strength, and hamstring/quadriceps ratio. In this study, following the season where 6 of the subjects had injured hamstrings, Lieholm was not able to find any significant difference in the isometric hamstring strength or in the hamstring/quadriceps ratio between the injured and uninjured athletes.

Heiser et al (1984) instituted a prerequisite isokinetic concentric hamstring/quadriceps ratio minimum of .60 at 60°/sec for collegiate footballers. This study found a significant difference in hamstring injuries following this, however they did state that their findings may have been confounded by the effects of a stretching and strengthening program that was implemented at the same time.

In contrast, Worrell et al (1991) found in their retrospective study of 16 hamstring injured university athletes matched to a control group that there was no significant difference in the injured subjects compared to the uninjured when comparing isokinetic concentric or eccentric strength at a peak torques of 60 and 180°.

Paton et al (1989) also found there was no significant difference between injured and noninjured soccer players in hamstring strength indices of isokinetic concentric hamstring/quadriceps ratio.

More recently, two studies have been performed on Australian Rules football players.

Orchard et al (1997) studied 37 players at an AFL club, where all the players were assessed preseason for measurements of hamstring and quadriceps concentric peak torque at 60, 180, and 300°/sec. Through out the season, the players were studied, and 6 suffered hamstring muscle injuries. This study found that according to their results, hamstring injuries were significantly associated with a low hamstring to quadriceps muscle peak torque ratio at 60°/sec on the injured side, with a lowered side to side hamstring peak torque ratio at 60°/sec.

Conversely, Bennell et al (1998) studied 102 Australian Rules footballers, investigating the relation of hamstring and quadriceps muscle strength and imbalance to hamstring injury. In this study, maximum voluntary concentric and eccentric torque of both muscle groups was measured on both legs. Over the season 12 players suffered hamstring injuries, and the study found that there was no significant difference in the muscle strength when comparing the injured to the noninjured legs of the players. In their conclusion, the authors felt that as there was no significant difference in their results, the use of preseason strength testing was limited.

Other authors have looked at the muscle imbalance between the hamstring muscles and the quadriceps.

Stanton and Purdam (1989) reviewed the role of eccentric hamstring muscle contraction with regard to hamstring injuries in sprinting. They concluded that in late swing phase if there is a weakness in eccentric muscle capabilities of the hamstring muscles, it might result in the series elastic component not being able to withstand the forces that are needed to decelerate the moving limb.

In the study carried out by Jonhagen et al (1994), 11 sprinters with hamstring injuries were compared with 9 non-injured sprinters. Eccentric and concentric muscle torques of the hamstrings and quadriceps were measured at 30, 180°/sec, concentric contractions at 270°/sec, and eccentric contractions at 230°/sec.

Fatigue

Hamstring injuries are more likely to be seen in the first or last quarter of a game such as Rugby Union or Australian Rules football. The latter can be attributable to fatigue occurring.

Altered coordination, technique or concentration as a result of fatigue has been proposed as a factor in hamstring injuries. The dual innervation of biceps femoris as an aetiological cause has been suggested (Agre, 1985), when fatigue causes the muscle to alter in its firing pattern and produce asynchrony with both heads activating at different times.

In one of the most recent studies, Pinniger et al (2000) investigated the affect of fatigue on muscle function. This study used dynamic effort to produce fatigue and measured the subjects in the non-fatigued condition and then the fatigued. The results of the study found that the fatigued condition induced an alteration of the biomechanics in the lower limb. Most of the changes were seen in the swing phase of gait. An increase in swing phase caused a decreased stride rate. Changes in muscle activation patterns caused changes in kinematics. The thigh angular velocity, and hip and knee flexion were decreased, with an increase in knee extension due to the hamstrings not being able to limit the end point of knee extension. A decrease in the angular displacement of the trunk thigh and leg were also noted, and these were thought to be part of a protective mechanism for the muscle. At toe off, increased extension of the thigh was seen which put the leg behind the total body centre of gravity. The activation of the hamstrings to decelerate the leg during swing was delayed, thus causing it to have to absorb a greater amount of energy in a shortened period of time. During stride, increased hamstring activity occurred with an early cessation of rectus femoris. The authors suggested that the changes seen in their study were used as protective mechanisms to protect the hamstrings during critical phases of the stride. However it may be suggested that failure of these protective mechanisms may lead to hamstring failure.

Flexibility

The relationship between hamstring injury and hamstring flexibility is another area of great debate. In retrospective studies, authors have been unable to determine whether hamstring tightness was the cause, or the reaction to injury (Jonhagen et al, 1994). Worrell et al (1991) stated that hamstring flexibility is the single most important feature in the hamstring injured player, however this was again a retrospective study, and it can not be used to determine aetiological factors.

In contrast, Hennessy and Watson (1993) found that in measuring the hamstring in injured players, there was no difference in the comparison with non injured players. Worrell et al (1994), and Hartig and Henderson (1999) have investigated the effect of hamstring flexibility on performance. Worrell et al (1994) found that increasing hamstring flexibility increased the performance of the hamstring in concentric and eccentric peak torque in selective isokinetic conditions. They do conclude that this does not prove that there is benefit in the closed chain situation, and more study needs to be done on this aspect.

Hartig and Henderson (1999) investigated the use of hamstring stretches to decrease the number of lower leg injuries in military trainees. They found that with an increase in flexibility there was a decrease in the number of injuries in the research group when compared to the control.

Flexibility of hamstrings has not been studied fully and as reported the majority of the research has been carried out in retrospective studies and therefore cannot determine conclusively whether or not hamstring length is a causative factor in the injury to the hamstring muscles.

Neural Mobility

Neural mobility is another factor thought to predispose to hamstring injury, however this, along with other aetiological causes has not been fully investigated.

Turl and George (1998) showed in their study of rugby union players that adverse neural tension, which they measures in a Slump Test, could contribute to or result from a Grade I hamstring strain. It should also be noted that a positive Slump Test could mimic a Grade I strain.

As a contributing factor to hamstring strains, increased neural tension in the sciatic nerve will cause a long-term impairment in the axoplasmic flow, and in turn leads to a mild inflammatory response in the muscle tissue. This affect predisposes the muscle to injury due to the disruption of its physiological and mechanical properties (Shacklock, 1995).

Decreased neural tension following hamstring injury is also seen. An injury to a muscle, especially recurrent strains, places repetitive strain on the neural tissue causing chronic inflammation, haemorrhage around the tissue, which eventually leads to adhesion formation that decreases neural mobility.

Posture and Recurrence

It has long been assumed that the risk of hamstring injury is greatly increased if an individual has suffered a previous hamstring injury. Many of the authors cited have stated this a dominant predisposing factor in hamstring injury, however there has been little research to either refute or support this claim.

Possible reason in the common recurrence of hamstring injuries, are an early return to sport with tight hamstrings, and also a loss of fast twitch muscle activity in the affected muscle, especially during eccentric loading.

Posture is another commonly talked about factor in the injuries of the hamstring, and another area that has been poorly investigated.

Hennessy and Watson (1993) while looking at hamstring flexibility also measured any postural faults in his subjects that had experienced hamstring injuries. He found that there were in fact postural differences in the injured subjects, but as this was a retrospective study, he was unable to identify whether or not they were a causative factor, or a result of the injury.

Clinical Implications

Following a review of recent and past papers, it is seen that all the above factors may have some bearing on hamstring injuries. However, it is also seen that there has not been a single factor that has been identified as the major influence of hamstring injuries. It is necessary, therefore, to consider all factors when treating hamstring injuries, and they all must be addressed in the rehabilitation of the athlete.

Worrell and Perrin (1992) proposed the following model involving the different causative factors proposed as identifiers to possible hamstring injury.

The confusion and debate concerning the importance of strength and flexibility regarding hamstring injuries, and with little known about the other factors, they suggested that the many factors are interrelated, and using their model, it is possible to consider the relationship between factors.

Summary

There has been little research into the predisposing factors of hamstring injuries, and the majority of the work that has been done, has mainly investigated strength and flexibility issues, with conflicting results being produced.

Another issue with regard to the research that has been undertaken is that the studies have been predominantly retrospective, and therefore have only surmised on the causative nature of the factors investigated.

It is important to consider in the treatment of athletes that all the factors discussed may play a role in the injury of a hamstring muscle. Therefore, they must all be addressed to promote the best possible environment for the healing muscle, and achieve the best possible rehabilitation for the athlete so as to prevent a recurrence of the injury, which is a common site for reinjury.

Further research is needed into the predisposing factors of hamstring injuries and prospective research on at risk populations appears to be the appropriate direction to take.

Short Answer Review Questions

1. Which of the hamstring muscles has dual innervation, and is thought to produce misfiring of the muscle in the fatigued condition? What is the nerve supply to this muscle?
2. What are the predominant muscle fibre types in the hamstring muscles?
3. At what stage during the swing phase of gait do the hamstring muscles start to fire?
4. In the final 1/3 of swing phase, what lower limb motions do the hamstrings control, and how are they acting?
5. At what point of the gait cycle do the hamstring muscles become quiet?
6. Does the literature support strength as a predisposing cause of hamstring injuries?
7. In the fatigued state, how does the gait cycle alter during sprinting?
8. How may neural tension cause a muscle injury in the hamstrings?
9. What is the effect of muscle injury on neural tissue, and how may it increase neural tension?
10. Due to what factors, may a recurrence of a hamstring injury occur?

References

Agre J (1985)

Hamstring injuries. Sports Medicine 2:21-33.

Bennell K, Wajswelner H, Lew P, Schall-Riaucour A, Leslie S, Plant D, and Cirone J (1998)

Isokinetic strength testing does not predict hamstring injury in Australian Rules footballers. British Journal of Sports Medicine 32: 309-314.

Burkett L (1970)

Causative factors of hamstring strains. Medicine and Science in Sports and Exercise 2:39-42.

Christenson C, and Wiseman D (1972)

The common variable in hamstring strains. Athletic Training 7:36-40.

Coole Wg, and Gieck JH (1987)

An analysis of hamstring strains and their rehabilitation. The Journal of Orthopaedic and Sports Physical Therapy 9:77-85.

Devlin L (2000)

Recurrent posterior thigh symptoms detrimental to performance in rugby union. Predisposing factors. Sports Medicine 29:273-287.

Elliot BC, and Blanksby BA (1979)

The synchronization of muscle activity and body segment movements during a running cycle. Medicine and Science in Sports and Exercise 11:322-327.

Hartig DE and Henderson JM (1999)

Increasing hamstring flexibility decreases lower extremity overuse injuries in military basic trainees. The American Journal of Sports Medicine 27:173-176.

Heiser TM, Weber J, Sullivan G, Clare P, and Jacobs RR (1984)

Prophylaxis and management of hamstring muscle injuries in intercollegiate football players. . The American Journal of Sports Medicine 12:368-370.

Hennessy L, and Watson AWS (1993)

Flexibility and posture assessment in relation to hamstring injury. British Journal of Sports Medicine 27:243-246.

Jonhagen S, Nemeth G, and Eriksson E (1994)

Hamstring injuries in sprinters. The role of concentric and eccentric hamstring muscle strength and flexibility. The American Journal of Sports Medicine 22:262-266.

Konnberg C, and LewP (1989)

The effect of stretching neural structures on grade one hamstring injuries. The Journal of Orthopaedic and Sports Physical Therapy 10:481-487.

Lieholm W (1978)

Factors related to hamstring strains. The Journal of Sprots Medicine 18:71-76.

Orchard J, Marsden J, Lord S, and Garlick D (1997)

Preseason hamstring muscle weakness associated with hamstring muscle injury in Australian footballers. The American Journal of Sports Medicine 25:81-85.

Pinniger GJ, Steele JR, and Groeller H (2000)

Does fatigue induced by repeated dynamic efforts affect hamstring muscle function? Medicine and Science in Sports and Exercise 32:647-653.

Shacklock M (1995)

Neurodynamics. Physiotherapy 81:9-16.

Stanton P, and Purdham C (1989)

Hamstring injuries in sprinting - the role of eccentric exercise. The Journal of Orthopaedic and Sports Physical Therapy 12:343-349.

Turl SE, and George KP (1998)

Adverse neural tension: A factor in repetitive hamsrting strain? The Journal of Orthopaedic and Sports Physical Therapy 27:16-21.

Worrell TE, Perrin DH, Gansneder BM, and Gieck JH (1991)

Comparison of isokinetic strength and flexibility measures between hamstring injured and noninjured athletes. The Journal of Orthopaedic and Sports Physical Therapy 13:118-125.

Worrell TE, and Perrin DH (1992)

Hamstring muscle injury: The influence of strength, flexibilty warm-up, and fatigue. The Journal of Orthopaedic and Sports Physical Therapy 16:12-18.

Worrell TE (1994)

Factors associated with hamstring injuries. An approach to treatment and preventative measures. . Sports Medicine 17:338-345.

Worrell TE, Smith TL, and Winegardner J (1994)

Effect of hamstring stretching on hamstring muscle performance. The Journal of Orthopaedic and Sports Physical Therapy 20:154-159.

Exercise Physiology Educational Resources 2000