The Effects of Acute Bilateral and Unilateral Set Protocols on Muscle Power and Rate of Force Development

Post activation potentiation (PAP) is used to improve the force generating capacity of skeletal muscles. However, no studies have examined if there is a difference in PAP response when comparing a unilateral versus a bilateral conditioning exercise. This is important because differences exist in muscle activation when comparing unilateral and bilateral exercises. Therefore, the purpose of this investigation was to determine if a unilateral exercise would cause a different PAP response compared to a bilateral exercise. Ten recreationally trained males participated (mean ± SD; age = 21.9 ± 2.1 yrs; body mass = 83.3 ± 10.5 kg; height = 1.8 ± 0.1 m; BMI = 25.8 ± 3.2; percent body fat = 14.8 ± 3.5%). Following a familiarization period and baseline strength testing all subjects completed 3 trials: unilateral, bilateral and control. Each trial consisted of a conditioning activity (4 reps at the 5RM load) followed by a maximal voluntary isometric leg extension contraction (60° knee extension) 7 minutes after finishing the conditioning activity. Neither conditioning activity (unilateral or bilateral squat) resulted in an increased peak torque value expressed in absolute or relative values as compared to control. Interestingly, following both conditioning activities, there was an increased time to reach half peak torque compared with the control trials (P <0.05). Our results demonstrated that neither conditioning activity prior to a maximal voluntary isometric contraction caused a PAP response. However, both conditioning activities appeared to cause residual fatigue. Kurt J Sollanek2, Scott W Talpey2 and Bülent Sökmen1* 1Department of Kinesiology, Sonoma State University, USA 2Departmentof Health Sciences and Psychology, Health Federation University, Australia Bülent Sökmen, et al., Sports Medicine and Rehabilitation Journal Remedy Publications LLC. 2017 | Volume 2 | Issue 1 | Article 1012 2 The apparent difference in strength between unilateral and bilateral exercise has been coined “the bilateral deficit” (BLD) and it has been well documented in the literature over the years [13,14]. Many proposed mechanisms underlie the BLD with a multitude of factors (e.g., muscle groups examined, contraction types used, subject training status, etc.) contributing to its presence and magnitude [12]. Nevertheless, unilateral exercises appear to have the potential to recruit a greater number of motor units and thus a greater percentage of muscle mass, when compared to bilateral exercises. Hypothetically, this enhanced recruitment could lead to a greater PAP response when used as a conditioning activity. Importantly, unilateral exercises can obtain maximal activation using a lighter absolute load, which may have clinical implications for PAP producing protocols [9]. For example, a clinician could rehabilitate an athlete and take advantage of the PAP response by using unilateral exercises with those athletes that may not be able to tolerate the heavy loads typically used in bilateral PAP producing protocols. Therefore, the purpose of this investigation was to determine if an intensity matched unilateral dynamic conditioning exercise would cause a different PAP response compared to a bilateral dynamic conditioning exercise on subsequent muscle contraction performance. This experiment is important for numerous reasons. First, if a difference in the PAP response appears between the different conditioning exercises (i.e., unilateral vs. bilateral), then practitioners would be wise to incorporate more of the movements that produce the greater response. Secondly, if there is no difference, this is very practical information, since many times adequately loading a bilateral movement is not appropriate in a clinical setting (i.e., 5RM back squat); therefore, a client or patient could more reasonably overload their muscles unilaterally in a clinical setting. Consequently, clinicians who aim to increase strength and power in individuals they are rehabilitating could use appropriately loaded unilateral exercises more than under-loaded bilateral exercises (e.g., body weight unilateral squats vs. body weight bilateral squats). Therefore, it stands to reason, that unilateral conditioning exercises may serve a greater role in enhancing the subsequent PAP response in a rehabilitation context. However, to our knowledge, this has not been carefully examined.