Neural and muscular changes to detraining after electrostimulation training
We investigated the effects of 4 weeks of detraining subsequent to an 8-week electrostimulation (ES) training program on changes in muscle strength, neural and muscular properties of the knee extensor muscles. Nine male subjects followed the training program consisting of 32 sessions of isometric ES training over an 8-week period. All subjects were tested before and after 8 weeks of ES training, and were then retested after 4 weeks of detraining. Quadriceps muscle anatomical cross-sectional area (ACSA) was assessed by ultrasonography imaging. The electromyographic (EMG) activity and muscle activation (i.e., by means of the twitch interpolation technique) obtained during maximal voluntary contractions (MVC) were used to examine neural adaptations. After training, the knee extensor voluntary torque increased significantly by 26%. Torque gains were accompanied by an increase in vastii EMG activity normalized to respective M-wave (+43%), muscle activation (+6%) and quadriceps ACSA (+6%). After detraining, knee extensor MVC, vastii EMG activity, muscle activation and quadriceps ACSA decreased significantly by 9%, 20%, 5% and 3%, respectively. Also, the knee extensor MVC values remained significantly elevated (14%) above baseline levels at the end of the detraining period and this was associated with a larger quadriceps ACSA (+3%) but not with a higher neural activation. We concluded that the voluntary torque losses observed after detraining could be attributed to both neural and muscular alterations. Muscle size preservation could explain the higher knee extensor MVC values observed after the cessation of training compared to those obtained before training, therefore indicating that muscle size changes are slower than neural drive reduction.
Effect of combined electrostimulation and plyometric training on vertical jump height.
APPLIED SCIENCES
Medicine & Science in Sports & Exercise. 34(10):1638-1644, October 2002.
MAFFIULETTI, NICOLA A.; DUGNANI, SERGIO; FOLZ, MATTEO; DI PIERNO, ERMANO; MAURO, FRANCO
Abstract:
MAFFIULETTI, N. A., S. DUGNANI, M. FOLZ, E. DI PIERNO, and F. MAURO. Effect of combined electrostimulation and plyometric training on vertical jump height. Med. Sci. Sports Exerc. Vol. 34, No. 10, pp. 1638-1644, 2002.
Purpose: This study investigated the influence of a 4-wk combined electromyostimulation (EMS) and plyometric training program on the vertical jump performance of 10 volleyball players.
Methods: Training sessions were carried out three times weekly. Each session consisted of three main parts: EMS of the knee extensor muscles (48 contractions), EMS of the plantar flexor muscles (30 contractions), and 50 plyometric jumps. Subjects were tested before (week 0), during (week 2), and after the training program (week 4), as well as once more after 2 wk of normal volleyball training (week 6). Different vertical jumps were carried out, as well as maximal voluntary contraction (MVC) of the knee extensor and plantar flexor muscles.
Results: At week 2, MVC significantly increased (+20% knee extensors, +13% plantar flexors) as compared to baseline (P < 0.05). After the 4-wk training program, different vertical jumps considered were also significantly higher compared to pretraining (P < 0.001), and relative gains were comprised between 8-10% (spike-counter movement jump) and 21% (squat jump). The significant increases in maximal strength and explosive strength produced by the present training program were subsequently maintained after an additional 2 wk of volleyball training.
Conclusion: EMS combined with plyometric training has proven useful for the improvement of vertical jump ability in volleyball players. This combined training modality produced rapid increases (~2 wk) of the knee extensors and plantar flexors maximal strength. These adaptations were then followed by an improvement in general and specific jumping ability, likely to affect performance on the court. In conclusion, when EMS resistance training is proposed for vertical jump development, specific work out (e.g., plyometric) must complement EMS sessions to obtain beneficial effects.