Signaling responses to high and moderate load strength exercise in trained muscle

Abstract

We examined signaling responses in the skeletal muscle of strength athletes after strength exercises under high and moderate load. Eight trained male powerlifters were recruited. The volunteers performed four sets of leg presses to volitional fatigue using a moderate load (65% 1‐repetition maximum [1 RM ]) for one leg, and a high load (85% 1 RM ) for the contralateral leg. The work volume performed by the leg moving a moderate load was higher than that of the contralateral leg moving a high load. Biopsy of the m . vastus lateralis was performed before, and at 1, 5, and 10 h after, cessation of exercise. Phosphorylation of p70S6k Thr389 , 4E‐ BP 1 Thr37/46 , and ACC S er79 increased after moderate load exercises, whereas phosphorylation of ERK 1/2 Thr202/Tyr204 increased, and that of eEF 2 Thr56 decreased, after high load exercises. Exercise under a moderate load and a high work volume activated mTORC 1‐dependent signaling in trained skeletal muscle, whereas exercise under a high load but lower work volume activated the MEK‐ ERK 1/2 signaling cascade and eEF 2.

Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum

“…Some studies show an impaired acute MPS response when training with lower loads [ 37 , 38 ] while others report similar increases in mixed and myofibrillar protein synthesis rates [ 39 ]. Other research demonstrates divergent responses in intracellular anabolic signaling and myogenic gene expression when training in moderate- (from 74% to 85% 1RM) and lower (from 54% to 65% 1RM) loading zones, with selective activation of different kinase pathways observed between conditions [ 40 , 41 ].…”

“…Consistent with this line of evidence, research where participants expended a high level of effort suggests that the MPS response to low-load training is at least as robust as when training with heavier loads [ 39 ]. That said, preliminary evidence for potential differences in intracellular anabolic signaling between loading zones cannot be discounted [ 40 , 41 ], and may have practical implications for RT program design. However, while acute studies on intracellular signaling and MPS are beneficial for understanding mechanisms and generating hypotheses for applied implications, results may not necessarily replicate over successive exercise trials.…”

Emphasizing Task-Specific Hypertrophy to Enhance Sequential Strength and Power Performance

“…In a recent observation of international level Russian powerlifters, hypertrophic responses were different for training groups using low loads, i.e., 65% 1RM, versus high loads, i.e., at 85% 1RM, indicating that training intensity can dictate hypertrophic outcomes specific to sporting tasks or competition demands [ 167 ]. Conversely, Norwegian national powerlifters produced preferential growth of type I muscle fibers (12%) compared to type II muscle fibers (4%) during a blood flow restriction training regimen where the training load remained low (i.e., ~30% 1RM), resulting in less effective hypertrophy [ 9 ].…”

“…These observations provide evidence that muscle plasticity gives rise to adaptions that reflect the training stimulus being applied. Understanding the force generation capabilities of each MHC isoform and the impact of these specific adaptations relative to the stimuli, the evidence indicates that there can be a selective hypertrophic response at the cellular level that is greatly influenced by training intensity [ 9 , 167 ]. Thus, for sports with competition tasks that require specific intra- and inter- muscular actions such as high-force, high-power, ballistic movements (i.e., powerlifting, weightlifting, throwing, strongman), increasing specific regional mCSA and the preferred molecular motors such as type II fiber content is warranted.…”

Pterins as diagnostic markers of exercise-induced stress: a systematic review

“…The type, duration and location of the stimuli directly reflects the changes and level of response in biological pathways. 1 Understanding the level of stress imposed by an exercise stimulus can inform on the level of exercise intensity, time to recovery from exercise, monitoring of over-training in untrained and trained individuals and assessing the efficacy of recovery interventions.…”