The aim of this investigation is to research if there are effects on postural sway and ankle stability when the quadricep muscles are fatigued. The hypothesis of this research is that there will be an effect on postural sway and ankle stability when the quadriceps are fatigued; the null hypothesis is that fatigue to the quadriceps has no effects on the participants’ postural sway and ankle stability. This research will seek to provide information of how different muscular voluntary contractions(MVC) can affect postural control. These results can aid to athletes, coaches and therapists on how fatigue may affect postural control which may help to increasing injury prevention in the lower body. Research into the effects on postural sway through fatigue has predominantly been on plantar flexors (Bisson, Chopra, Azzi, Morgan & Bilodeau, 2010). Studies involving other muscles have mainly been grouped for example ankle (Soleimanifar, Salavati, Akhbari & Moghadam, 2012), hip (Harkins, Mattacola, Uhl, Malone & McCrory, 2005). Therefore, the proposal of this research is to identify the effects the quadriceps have on postural sway and ankle stability. Furthermore, the research which has been carried out has been shown to use isokinetic contractions on the involved muscles within that project (Soleimanifar, Salavati, Akhbari & Moghadam, 2012).
Both daily living activities and sporting activities require constant postural control (Soleimanifar, Salavati, Akhbari & Moghadam, 2012). Although there is extensive research into lower extremity fatigue effecting postural sway and ankle stability, there are inconsistent results (Bisson, Chopra, Azzi, Morgan & Bilodeau, 2010); this could be caused through differential methods, procedures, equipment and participant backgrounds. Nonetheless, a predominant amount of research results show that postural sway does increase when lower extremity muscles are fatigued (Bisson, Chopra, Azzi, Morgan & Bilodeau, 2010; Paillard, 2012; Gimmon, Reimer, Oddson & Melzer, 2011). Postural sway is altered through muscular exercise (Paillard, 2012). This is due to the increase in contraction results in increased blood flow thus increased cardiac and respiratory muscle contractions (Bove et al., 2007). This is further amplified through sensory information and motor command being put under additional stress (Bizid et al., 2009). Vuillerme et al. (2006) researched how vision may affect these results. They found that although, calf muscles do reduce postural control, visual information can have a great effect on how much postural control is effected on a bipedal stance.
Force plates have predominantly been used to test centre of foot pressure (CoP) in determining postural sway. Rogind, Simonsen, Era & Bliddal (2003) carried out research to test the reliability and reproducible methods of using force plates in comparasion to a balance system; they found that the force platform was reliable, however at this point believed further research was required into the test-retest reliability. Quarman-Yates et al. (2013) conducted research to determine the test-retest reliability on postural control assessments using force plates. The results showed that there was a high long-term and short-term test-retest reliability. It was also sought that there were no learning effects on the procedures thus more accurate results in retesting.
Physiological activity can be easily traced through using an electromyography (EMG) (De Luca, 1997). They are mostly non-invasive in providing levels of muscular fatigue. The EMG contains signal which originates from the muscle but can also report unrelated noise components; this is effected more during dynamic movements in comparison to static contractions (De Luca, Gilmore, Kuznetsov & Roy, 2010). Other noises which can affect the results can include power line noises or cable noise. Cifrek, M., Medved, V., Tonkovic, S., & Ostojic, S. (2009) advise to use one pair of electrodes per muscle in a differential setup. When performing isometric contractions, the recommended frequency of the high-pass filter is recommended to be 20 Hz (De Luca, Gilmore, Kuznetsov & Roy, 2010). The detection surface of the electrodes should be perpendicular to the muscle fibres and the electrodes should be placed on the midline of the muscle belly, between the myotendinous junction and the nearest innervation zone (De Luca, 1997). A common issue on using EMG on leg muscles is getting cross information from nearby muscles, thus possibly providing am incorrect reading (De Luca, 1997). By following the recommendation, this can be minimised.
Methodology
Participants
The participants will be young adults, over the age of 18 and will be recreational athletes. Exclusion criteria include any injury which may affect postural control, any associated injury in the past 3 months, any medical condition which may affect postural control or any medical condition aggravated in exercise. The age, weight and height of each participant will be taken. They will be required to give informed consent (form in Appendix 1).
Equipment
A KinCom Isokinetic Dynamometer will be used to fatigue the muscle whilst an EMG tracks the muscle activity. Force plates will be used to measure postural sway through the CoP; they are fixed into the floor with a frequency of 1000hz.
Procedure
The EMG will be placed on the tibialis anterior, medial and lateral gastrocnemius, vastus medialis and bicep femoris and will be collecting data throughout the process. The participants will then take pre-fatigue reading. Participants stand on the force plates barefoot in a neutral stance. Participants hands must remain on hips throughout all stances. The participants first carry the activity out with their eyes open and then again with their eyes closed. Their head must remain facing forward and not look down at any point throughout the data collection; when eyes are open, a board will be placed 1m in front of the participant to reduce the chances of vision distance giving unreliable results. They will stand in a bipedal position for 20 seconds. They will then stand unipedal on the predominant leg for a maximum duration of 20 seconds or until they can no longer hold the position. They will then repeat on the opposite leg. The standing leg must remain straight and the lifted leg with the knee at a 90-degree angle. Bilateral and unilateral (right and left) stance data will be taken. The participants first carry the activity out with their eyes open and then again with their eyes closed. The participants will be split into two randomised groups (Group A and Group B). Participants will sit in the isokinetic dynamometer with the hip at 90-degree flexion and knee at 90-degree flexion and arms crossed over chest. All participants will be asked to carry out an isometric bilateral knee flexion to contract the quadriceps on the KinCom isokinetic dynamometer until the muscle has fatigued. The fatigue is measured when both legs have reached maximal exhaustion and are no longer able to carry out the contractions. Immediately after the muscles have reached fatigue, the participants will repeat the measurement procedures. The measurements will then be taken again at 2 minutes, 4 minutes, 6 minutes and 8 minutes to measure the muscle recovery. In the first session Group A will perform the contraction at 20% MVC and Group B will proceed at 60% MVC. The participants will then attend a second session one week later and Group A will carry out the contractions at 60% MVC and Group B at 20% MVC. An ANOVA will be run on the results to compare the CoP in the different stances, visual conditions, MVC.