The primary aim of this study was to compare rating of perceived exertion (RPE) values measuring repetitions in reserve (RIR) at particular intensities of 1 repetition maximum (RM) in experienced (ES) and novice squatters (NS). Furthermore, this investigation compared average velocity between ES and NS at the same intensities. Twenty-nine individuals (24.0 ± 3.4 years) performed a 1RM squat followed by a single repetition with loads corresponding to 60, 75, and 90% of 1RM and an 8-repetition set at 70% 1RM. Average velocity was recorded at 60, 75, and 90% 1RM and on the first and last repetitions of the 8-repetition set. Subjects reported an RPE value that corresponded to an RIR value (RPE-10 = 0-RIR, RPE-9 = 1-RIR, and so forth). Subjects were assigned to one of the 2 groups: (a) ES (n = 15, training age: 5.2 ± 3.5 years) and (b) NS (n = 14, training age: 0.4 ± 0.6 years). The mean of the average velocities for ES was slower (p ≤ 0.05) than NS at 100% and 90% 1RM. However, there were no differences (p > 0.05) between groups at 60, 75%, or for the first and eighth repetitions at 70% 1RM. In addition, ES recorded greater RPE at 1RM than NS (p = 0.023). In ES, there was a strong inverse relationship between average velocity and RPE at all percentages (r = -0.88, p < 0.001), and a strong inverse correlation in NS between average velocity and RPE at all intensities (r = -0.77, p = 0.001). Our findings demonstrate an inverse relationship between average velocity and RPE/RIR. Experienced squatter group exhibited slower average velocity and higher RPE at 1RM than NS, signaling greater efficiency at high intensities. The RIR-based RPE scale is a practical method to regulate daily training load and provide feedback during a 1RM test.

The maintenance of skeletal muscle mass is essential for health and quality of life. It is well recognized that maximal-intensity contractions, such as those which occur during resistance exercise, promote an increase in muscle mass. Yet, the molecules that sense the mechanical information and convert it into the signalling events (e.g. phosphorylation) that drive the increase in muscle mass remain undefined. Here we describe a phosphoproteomics workflow to examine the effects of electrically evoked maximal-intensity contractions (MICs) on protein phosphorylation in mouse skeletal muscle. While a preliminary phosphoproteomics experiment successfully identified a number of MIC-regulated phosphorylation events, a large proportion of these identifications were present on highly abundant myofibrillar proteins. We subsequently incorporated a centrifugation-based fractionation step to deplete the highly abundant myofibrillar proteins and performed a second phosphoproteomics experiment. In total, we identified 5983 unique phosphorylation sites of which 663 were found to be regulated by MIC. GO term enrichment, phosphorylation motif analyses, and kinase-substrate predictions indicated that the MIC-regulated phosphorylation sites were chiefly modified by mTOR, as well as multiple isoforms of the MAPKs and CAMKs. Moreover, a high proportion of the regulated phosphorylation sites were found on proteins that are associated with the Z-disc, with over 74% of the Z-disc proteins experiencing robust changes in phosphorylation. Finally, our analyses revealed that the phosphorylation state of two Z-disc kinases (striated muscle-specific serine/threonine protein kinase and obscurin) was dramatically altered by MIC, and we propose ways these kinases could play a fundamental role in skeletal muscle mechanotransduction.

The overarching aim of this study was to compare volume-equated high-repetition daily undulating periodization (DUPHR) versus a low-repetition daily undulating periodization (DUPLR) program for muscle performance. Sixteen college-aged (23 ± 3 years) resistance-trained males were counterbalanced into 2 groups: (i) DUPHR (n = 8), with a weekly training order of 12 repetitions (Day 1), 10 repetitions (Day 2), and 8 repetitions (Day 3); and (ii) DUPLR (n = 8), with a weekly training order of 6 repetitions (Day 1), 4 repetitions (Day 2), and 2 repetitions (Day 3). Both groups trained 3 times/week for 8 weeks on nonconsecutive days, with pre- and post-training testing during weeks 1 and 8. Participants performed only squat and bench press exercises each session. Changes in one-repetition maximum (1RM) strength, muscle thickness (MT), and muscular endurance (ME) were assessed. Both groups significantly increased 1RM strength for both squat and bench press (p < 0.01), and no group differences existed (p > 0.05). Similarly, both groups experienced significant increases in chest, lateral quadriceps distal, and anterior quadriceps MT (p < 0.05), but no change was present in either group for lateral quadriceps mid MT (p < 0.05). No group differences were discovered for changes in MT (p > 0.05). ME did not significantly change in the squat or bench press for either group (p > 0.05); however, for squat ME, a moderate effect size was observed for DUPHR (0.57) versus a trivial effect size for DUPLR (0.17). Our findings suggest that in previously trained males, training volume is a significant contributor to strength and hypertrophy adaptations, which occur independently of specific repetition ranges.

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