Acute neuromuscular fatigue, endocrine responses and recovery during maximal strength, hypertrophic and contrast training sessions in men

Abstract

Hypertrophic and maximal strength loadings are used among recreational athletes and athletes to improve maximal strength. Athletes often combine contrast movement with maximal strength or hypertrophic strength loadings to enhance transfer effect to power performance. However, there are a small number of studies that concentrates on the neuromuscular and endocrine responses between traditional strength loadings and contrast loadings in recreational athletes. The aim of the study was to observe acute neuromuscular fatigue, hormonal responses and recovery during five different strength loadings in men. A total of 11 recreationally strength trained men (26±4 years) participated in this study. Basal measurements of strength and familiarization were conducted before loadings. Subjects performed five different loadings in randomized order. Hypertrophic + countermovement jumps (HYP+CMJ) loading consisted of 3x10RM in leg press (LP) + 2x3x1xCMJ + 2x10RM in LP, hypertrophic loading (HYP) consisted of 5x10RM in LP, maximal + countermovement jump (MAX+CMJ) loading consisted of 5x1RM in LP + 2x3x1 CMJ + 5x1RM in LP, maximal loading (MAX) consisted of 10x1RM in LP and power + HYP consisted of 2x10xCMJ + 2x10xDJ + 2x2x5-Bound + 3x10RM in LP. Neuromuscular measurements included maximal isometric force in LP, average force of 100ms and 500ms, rate of force development (RFD), CMJ and EMG during CMJ and isometric LP. Serum testosterone, SHBG, cortisol, growth hormone and creatine kinase concentrations were measured. The measurements were conducted pre, post and during recovery, at post 24h and post 48h. Maximal force decreased significantly after every loading from pre to post (HYP+CMJ -15.8 ± 7.9% (p<0.05), HYP -18.8 ± 5.9% (p<0.001), MAX+CMJ -19.8 ± 5.3% (p<0.001), MAX -22.1 ± 9.4% (p<0.001) and power + HYP -13.4 ± 4.6% (p<0.01). RFD decreased significantly from pre to post (HYP+CMJ -30.0 ± 20.3% (p<0.05), HYP -25.1 ± 23.7% (p<0.05), MAX+CMJ -32.0 ± 14.5% (p<0.05), MAX -31.4 ±13.9% (p<0.01) and power + HYP -33.3 ± 24.7% (p<0.05). CMJ decreased after the HYP+CMJ, MAX+CMJ and MAX loadings, -11.1 ± 7.2% (p<0.001), -10.8 ± 6.1% (p<0.01) and -13.4 ± 5.9% (p<0.001), respectively and after the HYP loading the decrease was -7.0 ± 5.7% (p=0.079). The decrease in CMJ performance after combined power + HYP was -4.5 ± 12.1%. Neuromuscular performance recovered in 24h back to basal level. Intermit jumps after HYP loading session had an upward tendency and after the maximal loading sessions a downward tendency. Maximal force after MAX loading was significantly lower than after power + HYP (p<0.05). No other significant differences were observed in neuromuscular fatigue between loadings. Serum testosterone decreased from pre to post. Serum cortisol had also a tendency of reduction from the pre to post value. In conclusion, the present study showed that all five loadings induced acute neuromuscular fatigue, but 24 hours was enough to recover. These findings can be applied for planning subsequent strength loadings in training programs. Athletes can implement the results from the intermittent jumps in their warm-ups before power performances.