• Comparison of Muscle Activation in The Active Straight Leg Raise and Double Straight Leg Lowering Tests

      Callahan, Megan (2011-09-16)
      Muscle Activation during the Active Straight Leg Raise and Double Straight Leg Lowering Tests Callahan, ME. Gage, M. Ferng, SF. Nesser, T. Context: Low back pain is a common medical condition that exists in athletic and general populations. It is difficult to for clinicians to diagnose low back pain because no gold standard clinical test has been established to diagnose low back pain. Limited previous research has assessed muscle activation during commonly used clinical tests that evaluate low back pain. Objective: To assess transverse abdominis/internal oblique (TrA/IO), external oblique (EO), and rectus abdominis (RA) muscles during two common low back pain clinical tests. The clinical tests were the double straight leg lowering (DSLL) test and the active straight leg raise (ASLR) test. The ASLR was performed bilaterally. Design: Within subjects cohort study. Setting: Neuromechanics Research Laboratory. Participants: Thirty healthy, college aged, physically active (ht-173.48 + 9.15 cm, mass-73.85 + 17.1 kg, age-20.8 + 2. yrs) participants were recruited from a university campus. Intervention: Muscle activation was assessed during the DSLL and right (RASLR) and left (LASLR). Main Outcome Measures: Peak and mean abdominal muscle activation was measured using electromyography (EMG). Independent samples t-tests were used to assess muscle activation differences between tasks. Results: No differences were observed in the TrA/IO between the DSLL and ASLR. Greater iv mean muscle activation was observed in the EO [right-(p = .006) and left-(p = .020)] and RA [right-(p = .004) and left (p = .044)] during the DSLL than the RASLR. The EO [right-(p = .044) and left (p = .003)] and right RA (p = .002) had greater mean muscle activation during the DSLL than the LASLR. Greater peak EO [right-(p = .016) and left (p = .028)] and right RA (p= .003) muscle activation was observed during the RASLR than the DSLL. The left TrA/IO had greater peak muscle activation during the LASLR than the RASLR. Greater peak muscle activation was observed in the left EO (p = .005) and right RA (p = .001) during the LASLR and DSLL. The right TrA/IO (p = 0.45) had greater mean muscle activation during the RASLR than the LASLR. The left TrA/IO (p = .012) had greater mean muscle activation during the LASLR than the RASLR. Conclusion: The DSLL and ASLR do not assess the TrA/IO, EO, and RA in the same way. The ASLR recruits the TrA/IO more than the DSLL. The DSLL activates the EO and RA more than the ASLR. There are different activation patterns depending on the leg being raised during the ASLR.
    • The Effects of A Gluteus Medius Training Protocol on Muscle Activation and Postural Control

      Dorpinghaus, Nathan (2012-10-22)
      Context: Researchers have suggested a weak or dysfunctional gluteus medius (GM) has been linked to a number of lower extremity injuries. Identifying an appropriate intervention to prevent or correct GM deficits and determine associated outcomes has become a subject of increased interest. Objective: To determine if GM training changes lower extremity muscle activation during a dynamic task. Design: Controlled laboratory study. Setting: Biomechanics research laboratory. Participants: Eighteen healthy, physically active participants (7 men, 11 women; age=21.2±2.01yrs; height=168.39±8.92cm; mass=77.76±16.39kg) volunteered for the study. Each participant served as their own control. Intervention(s): Muscle activation of 5 trunk muscles were measured bilaterally before and after the protocol during a single-leg drop landing (45cm). All of the participants completed a six week GM training protocol. Main Outcome Measure(s): Peak and mean muscle activation was measured 400ms pre-and post-landing (pre-mean, pre-peak, post-mean, post-peak). Muscle activation data was normalized using maximal voluntary contractions. Results: No significant differences were observed during the control period. Decreased muscle activation was observed in the non-dominant GM [pre-mean (F1,17=14.301, P=.001), pre-peak (F1,17=9.490, P=.007), post-mean (F1,17=5.373, P=.033), and post-peak (F1,17=4.678, P=.045)]. Increased biceps femoris (BF) mean muscle activation was observed on the dominant leg pre-landing (F1,17=4.752, P=.044). Conclusions: Six weeks of GM training was enough time to observe improved neuromuscular efficiency of the GM. Increased BF muscle activation prior to landing suggests participants had an increased feedforward response in preparation for landing following training. Therefore, the combination of improved neuromuscular efficiency and a greater feedforward response suggest pelvic stabilization may be improved during a single-leg drop landing as a result of six weeks of GM training. This study suggests clinicians should incorporate bilateral GM exercises to improve lower extremity neuromuscular efficiency and feedforward responses which may improve pelvic stabilization. Key words: Electromyography, lower extremity injury, rehabilitation, neuromuscular efficiency, single-leg drop landing.