Neural and Metabolic Effects of Acute Fatigue Training

Neural and Metabolic Effects of Acute Fatigue Training

Dr. GJohn Mullen Blog, Competition, Training Leave a Comment

Combing aerobic and resistance training is common in swimming. This combination is termed concurrent training. Sometimes this type of training is used in dry-land, but it often occurs as swimmers swim prior to weight training.

Concurrent training is believed to improve strength, but the combination of endurance and strength training causes diminished increases in strength compared to strength training alone.

This inability to maximize strength during concurrent training is termed interference. Interference is theorized to occur secondary to the specificity of training/differential adaptation (endocrine and neuromuscular responses cell signaling in the form of AMP-activated protein kinase (AMPK) and Mammalian Target of Rapamycin (mTOR) and the acute fatigue theory.

The intent of this study was to compare how an acute fatiguing bout of cycle ergometry affects the metabolic and neuromuscular systems and subsequent upper (bench press) or lower body (back squat) resistance exercise performance.

What was done

Fifteen males were recruited for participation and at the initial visit performed 1-repetition maximum (RM) for back squat and bench. The next visit consisted of a graded exercise test on the cycle, ergometer to determine maximal heart rate. Subsequent visits consisted of the following testing criteria:

  •  a 45-minute bout of cycle ergometry at 75% maximum heart rate
  •  bench press at 80% 1-RM for six sets to voluntary failure
  • A 45-minute bout of cycle ergometry at 75% maximum heart rate
  • back squat at 80% 1-RM for six sets to voluntary failure

To track the metabolic and neuromuscular system, the researchers took blood lactate, electromyography (EMG), maximal voluntary contraction (MVC).

Results

Amount of repetitions in the bench press was not different with or without the 45-minute bout  of cycle ergometry. However, the back squat and 45-minute bout of cycle ergometry resulted in fewer repetitions. Lactate was significantly higher in the cycle ergometry trials. Triceps EMG and MVC was higher in the bench press the only trial.

Discussion

This study found moderate intensity lower extremity exercise prior to resistance training reduces impacts physical performance in the lower extremities. This is believed to occur due to fatigue and decreased glycogen content. The decrease in triceps EMG, but no change in the volume of repetitions suggests acute neuromuscular fatigue.

Practical Implication

In swimming, pool training is the most correlated for success. Therefore, decreases in strength gains outside the pool should not cause drastic changes in training. Moreover, out of water strength translating to pool success is questionable.

However, if the goal is to maximize out of water strength, then performing swimming (aerobic exercise) before weights may decrease strength gains.

Related Reading

Reference:

  1. Schilling BK, Reed JP, Murlasits Z. ACUTE NEUROMUSCULAR AND METABOLIC RESPONSES TO
    CONCURRENT ENDURANCE AND RESISTANCE EXERCISE. J Strength Cond Res. 2012 May 24.

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