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Can running in shoes impair stress on the Hamstring and Quadriceps’ Muscles in athletes? What are the implications of performance in a shoe?


An introduction

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Hamstring injuries are the most common injuries in sports that involve sprinting, and jumping. Running is a high-impact activity; it is well known that running shoes can help to protect the foot and, in general the lower extremity during this activity causing intensive loading on the lower body. An investigation will take place to try to find out why running related injuries occur and specifically to find the role of the shoe in supporting the hamstring and quadriceps musculature, as well as taking a closer look at the implications on muscular performance

The cause and effect of hamstring strains and injury in sport continues to be investigated, although evidence shows that the prevalence of this type of injury in activates involving sprinting for short bursts or prolonged effort remains high (Bennell et al, 1999, Thompson 2009, Pinnager et al 2000). It is commonly thought that ground reaction is responsible for the development of running related injuries (McNair & Marshall 2004). For example, evidence shows us that middle-distance runners experience impact forces (ground reaction force) upwards of 2 to 5 times bodyweight with each footfall (Clinhan et al 2007). The ground reaction forces experienced during each foot fall produce vibrations (shockwaves) which are transmitted by the bones of the foot to the rest of the body, and are continued through the CNS (Nigg & Wakeling 2001). The lower extremity vertical shock wave, resulting from ground reaction forces (the initial landing and loading response) is influenced by the position and orientation of joint axes, neuromuscular activity, and strength. (Goss et al 2005). The effect of running shoes on these factors is often underestimated. Shoes may allow excessive movement or may reduce unwanted movement. Since significant differences can be found in the peak pressure (approximately 20% body weight) and relative load patterns, shifting weight medially or laterally in different shoe constructions, the influence of footwear on the occurrence of overuse injuries should be obvious. (Goss et al 2005) The intensity of this ‘shockwave’ has been linked to the development of running-related injuries. An injury of course, is an absolute catastrophe for any serious competitor, so therefore must be avoided at all costs. It could be suggested that the unremitting shockwave experienced during running must be dampened by the athlete in order for the risks of overuse repetitive strain injuries to be minimised. .


Although many forms of running injuries have been reported no one study has come up with the ‘master’ conclusion of why these running injuries actually take place. Placing the athlete in shoes could minimise this stress at the main musculature around the knee joint, which may cause over training as the shoe will absorb the repeated vertical impact and therefore could potentially reduce injury risk. Footwear and orthoses can significantly alter the maximum EMG amplitude of leg muscles during walking. (Murely & Burke 2005). Fatigue of the hamstrings during running based activities and how this relates to excess stress bringing about injury has been documented (Pinnager et al 2000). It is clear that muscle activity in the leg can affect many aspects of locomotion, including skeletal position and velocity of the lower extremities, joint stiffness of the lower extremities, vibrations of soft tissue packages, joint loading, stability during ground contact, and propulsion for the movement task at hand (Nigg et al 2001). We must delve deeper into the above understanding to see exactly what happens to the body during a running based activity.
When we look at the functional anatomy of the hamstrings, we can see that the muscle group covers the posterior aspect of the thigh. The three muscles composing the hamstrings (semitendinosis, semimembranosus, and biceps femoris) are comprised of mainly fast Type II muscle fibers (Garrett at al, 1989). Each of the heads has separate innervations. 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 poster lateral aspect of the knee. The long head also helps to produce lateral rotation, extension and adduction at the hip joint. (http://physiotherapy.curtin.edu.au/resources/educationalresources/exphys/00/hamstring.cfm)
We are interested in the interaction between muscles and the joints aswell as the movement occurring during gait in order to make a thorough investigation on the stress imposed on the hamstrings and quadriceps during a barefoot and running footwear condition.

During the gait cycle a co-contraction occurs between the quadriceps femoris and the hamstrings to protect the ACL from excessive pull on the quadriceps, essentially the co-contraction can enable joint stiffness required to protect the knee joint. This contraction typically occurs during the first 25% of the gait cycle during loading response and early mid stance (Oatis (2002). As speed increases it is important to note that the length of time in stance phase decreases and therefore there is a period of time where both limbs are not in contact with the ground. Kyrolainen et al (2001) reported revealed the role of the powerful force production during ground contact and the importance of activation of the leg extensors during the pre-activity and braking phases and their coordination with longer lasting activation of the hamstring muscles. It may also be suggested that proper co-activation of muscle around the knee and ankle joints are needed to increase the joint stiffness to match the requirement for increase in running speed. The shoe may absorb the loading during running this may effect the recruitment of the hamstrings and quadriceps, the question is whether this could act as a hindrance to the development of the athlete.

The hamstrings are responsible for the deceleration on the hip and knee during running and the quadriceps are the main controller as the knee flexes and extends during the first 25% of the early mid stance phase. During the forward swing the semimembranosus activates producing eccentric work to decelerate flexion of the thigh (Thompson 2009). Semimembranosus and semitendinosis increase in activity to reverse the thigh direction and decelerate the tibial extension, while the biceps femoris has been reported to be 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 hip flexion. According to Oatis (2002) the Hamstrings begin their activity with an eccentric contraction in the late swing phase but their subsequent length is difficult to discern since loading response at the hip is extending whilst the knee is flexing. The ‘stretch shortening cycle’ allows the hamstring and the quadriceps to stretch enabling an initiation of force and power production, as well as storing energy and exhibits the length change in the hamstrings during the loading phases of gait. Oatis (2002) proposes that the lengthening contractions that begin when muscle activity in gait decelerate each joint and then subsequent concentric contractions begin the joints forward movement.


Just before heel strike, the hamstrings work concentrically briefly to prepare for weight In order to summarise we can say that the hamstrings and the quadriceps are responsible for controlling supporting as well as propelling the knee joint so it is important that they do not suffer undue stress do to conditions such as bare foot running or running in incorrect footwear.

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).

Prilutsky et al (1998), suggest that there is a strong correlation between the difference in electromyography activity (EMG) of rectus femoris (RF; hip flexor and knee flexors) and the difference in the resultant moments at the knee and hip. This relationship means that activity of RF increases and activity of HA decreases with increasing flexion moment at the hip and extension moment at the knee. Bennell et al (1999) report that Injuries typically occur during foot strike and late stance phase as the hamstring works eccentrically to control the lengthening phase over the hip and knee joints. This high eccentric force must absorb the active contractile tissue and the passive series elastic components of the muscle, in short it can help to absorb the energy. Oatis (2002) propose that vertical GRF contribute significantly to joint reaction forces contribute to pain in patients with joint pathology such as arthritis. Furthermore, an investigation will take place on how we can minimize stress imposed from running and protect the bones in the leg via the musculature from the cushioning found within running shoes. It could be reasonably suggested that the hamstrings and quadriceps are subjected to repetitive impact force, an input which can add stress onto the musculature around the knee. This stress surely is to be minimised in order to protect the runner’s knee from harm. It is hypothesised therefore that running in shoes will soften the ‘blows’ which are encountered by these muscles during the push and pulling and propelling actions and therefore protect the muscles from overloading. In the same instance, it is also hypothesised that running in a barefoot could maximise the impact and add undue stress on to the floor and could be a potential for injury.

It cannot be overlooked that the scientific advantages of the shoe has been the objective of marketing strategies for some of the world’s most prestigious brands of running footwear. However, despite these massive progressions in technology and industry design such as increased cushioning and orthotics, evidence shows that that the incidence of running injuries continues to remain as highly reported risk, Hart & Smith (2008).

Much more recent evidence reveals a flip side to the argument, showing that running shoes can incur further stress on the musculature than a bare foot condition. This maybe due to the fact that the shoe does not let the foot move naturally as described by Wilk et al (2009) who have very recently reported within their study of the Nike Free designed footwear that this is the case. Divert et al (2005) concluded that when performed on a sufficient number of steps, barefoot running actually leads to a reduction of impact peak in order to reduce the high mechanical stress occurring during repetitive steps. This neural-mechanical adaptation could also enhance the storage and restitution of elastic energy at ankle extensors level. Therefore must an athlete must consider other factors per se. The athlete may need to consider maximizing muscle contraction during their training in order to generate maximum power and force during activities such as sprinting.






Methods
Subjects
Approval for the investigation was obtained from The University of Sydney Human Ethics Committee (Reference Number: 99/01/31). ?? Gave their informed consent to participate in the experiment. A visual inspection of the first running trial was used to ensure that the subject jogged naturally with heels striking the ground first. Calcaneal inclination was measured as in Hunt et al (2000).
Experimental design
Two footwear conditions were evaluated, barefoot, regular shoes and motion control shoes (featuring dual density midsoles and an extended DuoMax® medial post, Asics Tiger GT 2040TM). SpEVA TM was used only for the lower density midsole region in the GT 2040. The barefoot condition was included to show that the wand motion accurately reflected rear foot motion and as a baseline for the main effect of footwear. Each subject executed five trials of each condition to ascertain the reliability of the protocol and provide a representation (mean of the time normalized data) of the performance in each condition.
Equipment
Motion Capture Devices
Fourteen cameras (Eagle High Speed, High Resolution, Motion Analysis Corporation, Santa Rosa, California) were used to record the positions of retro reflective markers on the right leg. The cameras were set at a frame rate of 200 Hz. The cameras were arranged in a circle close to the force platform to maximize the resolution of marker positions in three dimensions.
A force plate (9287b, KistlerTM, Switzerland) with a sampling rate of 1000 Hz was located in the running surface to obtain the ground reaction force and thus determine heel strike and toe-off during the stance phase. Data collection was controlled by the motion analysis measurement system (Cortex 1.0, Motion Analysis Corporation, Santa Rosa, California). Before data collection, the capture volume above the force plate was calibrated and laboratory coordinate system defined, first with a rectangular seed calibration frame comprising four spherical markers arranged in L shape. Then, a wand with 3 markers was swept through the capture volume for calibration of the space and compensation for lens distortion.



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