Background/Aim: Exercise designed to condition the lumbar extensor musculature is often included in resistance training (RT) programs. It is suggested that deconditioning of this musculature may be linked to low back pain. Thus effective means of conditioning these muscles are of interest to pursue. Evidence suggests that isolated lumbar extension (ILEX) RT might be most efficacious, however, the best means of manipulating resistance training variables in this regard is unknown. Set volume is

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... easily manipulated RT variable and one thought to also interact with training status. As such this study sought to examine the effect of set volume during ILEX RT in trained males. Methods: Trained males previously engaged in exercises designed to condition the lumbar extensors underwent a 6 week intervention and were randomised to either a single set (1ST, n = 9), multiple set (3ST, n = 8) or control group (CON, n = 9). Pre and post testing of ILEX strength was conducted. Results: Both 1ST and 3ST significantly increased ILEX strength (p < 0.05) with large effect sizes (d = 0.89 and 0.95 respectively) whereas the CON group produced significant losses (-8.9%) with a moderate effect size (d = -0.53). There was no statistically significant difference in ILEX strength gains when 1ST and 3ST were directly compared (p = 0.336). Conclusions: The results of this study suggest that significant ILEX strength changes occur in trained males as a result of 6 weeks of ILEX RT and that these changes are unaffected by set volume. PeerJ reviewing PDF | (31 Haykowsky, 1999). The use of resistance training (RT) to reduce injury risk has been suggested (Stone, 32 1990) and a systematic review has recently reported it to reduce sporting injury risk by one third 33 (Lauersen et al., 2013). As evidence seems to suggest that deconditioning of the lumbar extensor 34 musculature (lumbar erector spinae, multifidus, and quadratus lumborum) may be a factor associated 35 with LBP and increased injury risk (Steele et al., 2014 a ) research has attempted to evaluate the best 36 approaches for conditioning this musculature through RT. 37 Mayer et al. (2008) have suggested differing exercise approaches to condition the lumbar 38 extensors which have recently been reviewed with evidence suggesting that, due to the restraint system 39 preventing rotation of the pelvis, isolated lumbar extension (ILEX) exercise devices may be optimal 40 (Steele et al., 2013). However, when considering an RT programme, variables such as load, effort, 41 repetitions, repetition duration, volume, frequency, etc. should also be considered (American College of 42 Sports Medicine, 2009; Fisher et al., 2011). The manipulation of such variables when employing ILEX 43 has been reviewed when considering patients suffering with chronic LBP for outcomes such as pain and 44 disability (Steele et al., 2014 b ), but does not exist for asymptomatic people who may be interested in 45 injury prevention. 46 However, a number of studies have considered asymptomatic individuals, and the effect of RT 47 variable manipulation upon ILEX strength as an outcome examining the volume, frequency, specificity 48 and range of motion during training, considering both previously untrained participants (Graves et al.