Short-Term Effect of Plyometrics and Strength Training with and without Superimposed Electrical Stimulation on Muscle Strength and Anaerobic Performance

Purpose Compare the effects of combined strength & plyometric training with or without superimposed electromyostimulation (EMS) on muscle strength and anaerobic power. – Superimposed EMS= performing a voluntary contraction while EMS is applied simultaneously.

Why? Shown in previous studies: – Superimposed EMS alone leads to ↓ Vertical Jump → Sprint Time ↑ Muscle Strength -Isometric EMS + Plyometrics leads to ↑ Vertical Jump ↓ Sprint Time ↑ Muscle Strength

Why continued… However, since pain is the limiting factor for isometric EMS, intense pain and discomfort can inhibit this type of training. It is shown that when a voluntary contraction is performed while EMS is applied, pain and discomfort can be greatly reduced. Greater anaerobic gains possible?

Hypothesis Combining SEMS + Plyometric training should enhance anaerobic performance. SEMS + Plyos = ↑ Vertical Jump ↓ Sprint Time

Study Design A randomized, controlled trial with 2 treatment groups and 1 control group with repeated measures outcome assessments over a 6-week period 29 male, physical education students volunteered for the study. Grouping – Weight + Plyos + EMS (EP group) – Weight + Plyos (VP group) – No treatment (CG/control group)

Methods Independent variables: Time the measurements were taken (Before, 3 to 4 days after, and 2 weeks after training) Dependant variables: – Maximal Voluntary Contraction [Leg Extension] (MVC) – Squat Jump (SJ) – Counter-movement jump (CMJ) – Counter-movement jump w/ free arms (CMJ A ) – Sprint Time (ST)

Results Weights + Plyos with or without superimposed EMS – Increased muscle strength – Improved sprint performance – Did not modify vertical jump (except in CMJ A where a decrease was observed The increment in muscle strength increase was greater for the group with EMS added versus voluntary training alone.

Results

Generalize to untrained subjects. Results may vary for trained individuals. Its possible that you would see more dramatic gains when using untrained over trained subjects. The only positive relationship is with the muscle strength and sprint time. We see a negative relationship with the countermovement jump with arms. There an insignificant relationship with the squat jump because it’s the same as the control group as well as the countermovement jump with out arms. It was a sample of convenience that was taken from a physical education department. The subjects were randomly assigned to each one of the control groups. External Validity

Has temporal precedence. Has co variation of cause and effect. No single group threat because there were three different groups. There is no multiple group threat as well because there was random assignment. Compensatory rivalry, the VP could have found out that they weren’t getting EMS treatment so they tried harder. Showed greater improvement on both the counter movement jumps. Internal Validity

Study design R Pre x1 Post… Post R Pre x2 Post… Post R Pre Post… Post

Mono-operation bias – Leg extension – Plyometrics Social threats Confounding constructs/levels of constructs Mono-method bias Construct Validity