Introduction: 

The phosphorylation of stress responsive kinases AKT and ERK is augmented in response to resistive exercise thus potentially reflecting the magnitude of resistance exercise induced stress and also subsequent adaptation.

Purpose: 

Resistance exercise differing in intensity and training volume may excite distinct patterns in AKT and ERK phosphorylation in muscle lysates and also in type I and II myofibers. Thus It was aimed to investigate the phosphorylation levels between different modes of resistance exercise over an expanded time course. The resistance exercise stimuli were built to be comparable to practical applications in the fed state.

Methods: 

Muscle biopsies were taken from 21 males (24±3 years) PRE, 15, 30, 60, 240 min and 24 hours after acute bouts of single leg knee extensions. AKT THR³⁰⁸ and ERK 1/2 Thr²⁰²/Tyr²⁰⁴ phosph. was determined by western blotting and immunohistochemistry. Resistance exercise modes: Standard (SR n=7) 3 sets 10 repetitions 75% max. dynamic force (MDF); High intensive (HIT n=7) 1 set 20 rep. 100 % MDF; Eccentric (EC n=7) 3 sets 8 rep. eccentric contraction, 100 % MDF.

Results: 

A 2 fold increase in AKT phosph was observed in SD 15 min after exercise (p<0,01). AKT phosph. peaked not significant in HIT (p=0.24) and EX (p=0.15) 60 min after training. There were no differences in AKT phosph. between groups. ERK 1 phosph. differed significant between HIT and SD (p<0.05) over the time course but not between (HIT- EC) or (SD - EC). ERK 2 phosph. was not different between exercise modes and any time point. AKT phosph. in myofibers did not differ between exercise modes and fiber type. In any exercise mode AKT phosph. peaked 15 and 30 min after exercise (p<0.05). ERK phosph. in myofibers was biphasic modulated but not statistically different between training modes. For the entire collective ERK phosph. differed (p<0.01) between type I and II fibers.

Conclusion: 

High interindividual variabilities in phosph. levels were observed, potentially reflecting individual responses towards exercise. Although HIT and EC tended to be more effective in increasing phosph. levels.of AKT and ERK, different exercise modes elicit no statistically different responses. The results show one set of intensive resistance exercise HIT to excite at least equal signaling magnitudes as multiple sets SD or EC.