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 (CMJA)
Sprint Time (ST)
Results
• Weights + Plyos with or without superimposed EMS
– Increased muscle strength
– Improved sprint performance
– Did not modify vertical jump (except in CMJA where a
decrease was observed
• The increment in muscle strength increase was
greater for the group with EMS added versus
voluntary training alone.
Results
External Validity
• 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.
Internal 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.
Study design
R Pre x1 Post… Post
R Pre x2 Post… Post
R Pre
Post… Post
Construct Validity
• Mono-operation bias
– Leg extension
– Plyometrics
• Social threats
• Confounding constructs/levels of constructs
• Mono-method bias