Kontos, N. J. | Search bioRxiv

bioRxiv2023

Hip thrust and back squat training elicit similar gluteus muscle hypertrophy and transfer similarly to the deadlift

PurposeWe examined how set-volume equated resistance training using either the back squat (SQ) or hip thrust (HT) affected hypertrophy and various strength outcomes. MethodsUntrained college-aged participants were randomized into HT or SQ groups. Surface electromyograms (sEMG) from the right gluteus maximus and medius muscles were obtained during the first training session. Participants completed nine weeks of supervised training (15-17 sessions), before and after which we assessed muscle cross-sectional area (mCSA) via magnetic resonance imaging and strength via three-repetition maximum (3RM) testing and an isometric wall push test. ResultsGlutei mCSA growth was similar across both groups. Estimates [(-) favors HT; (+) favors SQ] modestly favored the HT compared to SQ for lower [effect {+/-} SE, -1.6 {+/-} 2.1 cm2], mid [-0.5 {+/-} 1.7 cm2], and upper [-0.5 {+/-} 2.6 cm2], but with appreciable variance. Gluteus medius+minimus [-1.8 {+/-} 1.5 cm2] and hamstrings [0.1 {+/-} 0.6 cm2] mCSA demonstrated little to no growth with small differences between groups. Thigh mCSA changes were greater in SQ for the quadriceps [3.6 {+/-} 1.5 cm2] and adductors [2.5 {+/-} 0.7 cm2]. Squat 3RM increases favored SQ [14 {+/-} 2.5 kg] and hip thrust 3RM favored HT [-26 {+/-} 5 kg]. 3RM deadlift [0 {+/-} 2 kg] and wall push strength [-7 {+/-} 13 N] similarly improved. All measured gluteal sites showed greater mean sEMG amplitudes during the first bout hip thrust versus squat set, but this did not consistently predict gluteal hypertrophy outcomes. ConclusionNine weeks of squat versus hip thrust training elicited similar gluteal hypertrophy, greater thigh hypertrophy in SQ, strength increases that favored exercise allocation, and similar strength transfers to the deadlift and wall push.

physiology↗

bioRxiv2022

Skeletal muscle DNA methylation and mRNA responses to a bout of higher versus lower load resistance exercise in previously trained men

We sought to determine the skeletal muscle genome-wide DNA methylation and mRNA responses to one bout of lower-load (LL) versus higher-load (HL) resistance exercise. Trained college-aged males (n=11, 23{+/-}4 years old, 4{+/-}3 years self-reported training) performed LL or HL bouts to failure separated by one week. The HL bout (i.e., 80 Fail) consisted of four sets of back squats and four sets of leg extensions to failure using 80% of participants estimated one-repetition maximum (i.e., est. 1-RM). The LL bout (i.e., 30 Fail) implemented the same paradigm with 30% of est. 1-RM. Vastus lateralis muscle biopsies were collected before, 3 hours, and 6 hours after each bout. Muscle DNA and RNA were batch-isolated and analyzed using the 850k Illumina MethylationEPIC array and Clariom S mRNA microarray, respectively. Performed repetitions were significantly greater during the 30 Fail versus 80 Fail (p<0.001), although total training volume (sets x reps x load) was not significantly different between bouts (p=0.571). Regardless of bout, more CpG site methylation changes were observed at 3-versus 6-hours post exercise (239,951 versus 12,419, respectively; p<0.01), and nuclear global ten-eleven translocation (TET) activity, but not global DNA methyltransferase activity, increased 3- and 6-hours following exercise regardless of bout. The percentage of genes significantly altered at the mRNA level that demonstrated opposite DNA methylation patterns was greater 3- versus 6-hours following exercise (~75% versus ~15%, respectively). Moreover, high percentages of genes that were up- or downregulated 6 hours following exercise also demonstrated significantly inversed DNA methylation patterns across one or more CpG sites 3 hours following exercise (65% and 82%, respectively). While 30 Fail decreased DNA methylation across various promoter regions versus 80 Fail, transcriptome-wide mRNA and bioinformatics indicated that gene expression signatures were largely similar between bouts. Bioinformatics overlay of DNA methylation and mRNA expression data indicated that genes related to "Focal adhesion", "MAPK signaling", and "PI3K-Akt signaling" were significantly affected at the 3- and 6-hour time points, and again this was regardless of bout. In conclusion, extensive molecular profiling suggests that post-exercise alterations in the skeletal muscle DNA methylome and mRNA transcriptome elicited by LL and HL training bouts to failure are largely similar, and this could be related to equal volumes performed between bouts.

molecular biology↗