Quick Overview
Scientists at the Federal University of São Paulo ran a randomized trial on 36 teen volleyball athletes.
hey added EMS, used as NMES on the quadriceps, to the same six-week training plan.
A blinded tester measured leg muscle strength in N/kg, jump-and-reach height, two-minute jump count, and jump feel.
The NMES group rose from 6.9 to 9.5 N/kg on the dominant leg and from 7.1 to 10.9 N/kg on the other. Versus control, those gaps reached 1.8 and 3.1 N/kg at week eight. Jump height rose 5.3 cm inside the EMS group.
Springer published the ethics-approved, registered study.
Read the full post for every figure.
We always provide direct links to the original research at the end of every article so you can review the evidence yourself.
Volleyball Players Built More Leg Strength When Training Included EMS, São Paulo Trial Finds
Young volleyball players live and die by the jump.
Stronger legs can mean a cleaner block.
They can also mean a sharper spike.
In 2015, researchers in São Paulo asked a simple training question.
Could adding EMS, used here as NMES, help that jump work land harder?
They did not guess.
They ran a registered trial.
Why this write-up sits on real science
The work came from the Federal University of São Paulo.
That is a major public research university in Brazil.
The team sat in orthopaedics, traumatology, and physical therapy.
Lead author Ronaldo Alves da Cunha worked with Carlos Eduardo Pinfildi, Alberto de Castro Pochini, and Moisés Cohen.
The ethics board approved the protocol.
The trial was listed on ClinicalTrials.gov as NCT02443701.
Springer published the paper in Lasers in Medical Science in 2020.
That journal is a peer-reviewed science title.
The study is a randomized controlled trial, not a fan story.
This post reports what that paper measured.
It is not medical advice.
It does not sell a device.
It does not claim EMS treats injury, illness, or disease.
What the scientists set out to learn
The purpose was clear.
Could photobiomodulation or NMES add extra value to normal volleyball training?
The team wanted numbers on muscle strength.
They also tracked jumping skill.
They checked those marks after six weeks.
They checked again two weeks after training stopped.
Who took part
Thirty-six male athletes made the cut.
Each was 17 or 18 years old.
Each had at least 12 months of volleyball experience.
None had a recent lower-limb injury.
A doctor had cleared them for hard work.
They trained at a high-performance centre in São Paulo.
Researchers split them into three groups of 12.
One group did training only.
One added laser-style photobiomodulation before work.
One added NMES during quadriceps strength work.
Every player finished all 18 sessions.
Nobody dropped out at week six or week eight.
How the EMS group trained
All groups warmed up on a bike.
Then they did isometric leg-extension work.
They also did countermovement jump sets.
The NMES group used the same gym plan.
EMS pads sat on the quadriceps.
One electrode sat on rectus femoris.
The other sat on vastus medialis.
The current used a 1 kHz base.
It was modulated at 70 Hz.
On-time was 10 seconds.
Off-time was 30 seconds.
Intensity rose to the highest level each player could tolerate.
That is sports training work, not a clinic claim.
What they measured
A blinded tester checked both legs.
Muscle strength came from a handheld dynamometer.
Scores were reported in newtons per kilogram.
Jumping height came from a jump-and-reach test.
Players also did two minutes of repeated jumps.
They rated how their jump felt on an 11-point scale.
Tests happened before training.
They happened after six weeks.
They happened again at eight weeks.
The strength numbers that stood out
Every group got stronger.
The NMES group moved furthest.
On the dominant leg, NMES athletes rose from 6.9 to 9.1 N/kg after six weeks.
At eight weeks they sat at 9.5 N/kg.
That within-group climb was 2.5 N/kg after training.
It was 2.6 N/kg at the late check.
Against the control group, dominant-leg strength favoured NMES.
The gap was 1.4 N/kg after six weeks.
The 95% confidence interval ran from 0.5 to 2.4.
At eight weeks the gap was 1.8 N/kg.
That interval ran from 0.6 to 3.0.
The non-dominant leg told a brighter story still.
NMES scores rose from 7.1 to 9.8 N/kg after six weeks.
They reached 10.9 N/kg at week eight.
That late within-group gain was 3.7 N/kg from baseline.
Players even added another 1.0 N/kg after formal training stopped.
Versus control, non-dominant strength favoured NMES by 1.9 N/kg at six weeks.
The interval ran from 1.1 to 2.8.
At eight weeks the gap was 3.1 N/kg.
That interval ran from 2.0 to 4.3.
In short, the same gym plan plus EMS was linked with more measured strength.
What happened to the jump
Jump height inside the NMES group rose by 5.3 cm after six weeks.
The interval ran from 1.4 to 9.3 cm.
From baseline to week eight the rise was 4.3 cm.
Raw means went from 54.6 cm to 60.4 cm, then 59.3 cm.
Those within-group changes were statistically clear.
Head-to-head gaps versus control were not.
Jump count in two minutes also rose inside the NMES group.
The six-week change was 6.9 jumps.
The eight-week change was 7.7 jumps.
Players also scored their jump feel higher.
NMES beat control by 1.1 points after six weeks on that scale.
So the cleanest signal was muscle strength.
Jumping improved inside the EMS group.
It did not always beat the other groups by a wide statistical margin.
The bright reading, kept honest
This trial does not say EMS replaces squats, plyometrics, or coaching.
It says something narrower, and useful.
When young volleyball athletes added NMES to the same training block, their legs tested stronger.
Those strength gains were still there two weeks after the extra work stopped.
On the non-dominant side, the EMS group also outpaced the laser group.
That is the “added work, extra mark on the sheet” finding.
More training stimulus sat beside more measured strength.
That is the bright side the data can carry.
It is not a promise that endless sessions always win.
What this means for players and coaches
If you coach junior volleyball, treat this as sports science, not a miracle ad.
The paper supports a careful idea.
EMS, used as NMES on the quadriceps, can sit beside gym work.
In this sample it was linked with larger isometric strength scores.
Some jumping scores also moved in the right direction inside that group.
Keep the limits in view.
The sample was 36 teen males in one Brazilian centre.
Testers were blinded.
Players and trainers were not.
Jump height did not clearly beat control between groups.
Read it as evidence from a proper trial.
Do not read it as a treatment claim.
The takeaway
Trustworthy scientists in São Paulo ran a real randomized trial.
A major university backed it.
A Springer journal published it.
Their purpose was to test extra tools on volleyball training.
The EMS arm produced the strongest muscle strength signal.
That is the evidence this study actually put on the page.
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Research Summary
| Detail | Information |
|---|---|
| Study title | Photobiomodulation therapy and NMES improve muscle strength and jumping performance in young volleyball athletes: a randomized controlled trial study in Brazil |
| Purpose | Test whether adding NMES (a form of EMS) or photobiomodulation to volleyball training improved muscle strength and jumping |
| Original study | Springer journal page · PubMed · DOI 10.1007/s10103-019-02858-6 |
| Trial register | ClinicalTrials.gov NCT02443701 |
| Authors | Ronaldo Alves da Cunha, Carlos Eduardo Pinfildi, Alberto de Castro Pochini, Moisés Cohen |
| Institution | Federal University of São Paulo (UNIFESP), Brazil; high-performance training centre in São Paulo |
| Publisher and journal | Springer, Lasers in Medical Science (2020) 35:621–631; online 11 August 2019 |
| Design | Prospective randomized controlled trial; opaque sealed envelopes; intention-to-treat; blinded assessor and statistician |
| Participants | 36 male volleyball athletes, 17–18 years old, ≥12 months experience; 12 per group; no dropouts |
| Groups | Control (training only); photobiomodulation plus training; NMES/EMS plus training |
| Training plan | 18 sessions over 6 weeks, 3 times weekly; isometric quadriceps work plus countermovement jumps; follow-up at 8 weeks |
| EMS / NMES method | Quadriceps pads on rectus femoris and vastus medialis; 1 kHz carrier, 70 Hz modulation, 10 s on / 30 s off, maximum tolerable intensity |
| What was measured | Handheld-dynamometer strength (N/kg), jump-and-reach height (cm), 2-minute jump count, global perceived jump score |
| Dominant-leg strength | NMES group: 6.9 → 9.1 → 9.5 N/kg; vs control +1.4 N/kg at 6 weeks (95% CI 0.5 to 2.4) and +1.8 at 8 weeks (0.6 to 3.0) |
| Non-dominant-leg strength | NMES group: 7.1 → 9.8 → 10.9 N/kg; vs control +1.9 N/kg at 6 weeks (1.1 to 2.8) and +3.1 at 8 weeks (2.0 to 4.3) |
| Jumping scores | NMES jump height rose 5.3 cm within group after 6 weeks (54.6 to 60.4 cm); between-group jump gaps vs control were not statistically significant |
| Persistence | Strength gains in the NMES group were still present 2 weeks after the extra training stopped |
| Authors’ conclusion | For these volleyball athletes, NMES and photobiomodulation both aided muscle-strength gain; NMES showed the larger strength signal versus control |
| Limits to keep in view | Small all-male teen sample; players and trainers not blinded; jump height did not clearly beat control between groups; sports-training research, not a medical-treatment claim |
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