I can't imagine what, exactly, you'd be looking for.
I'm not sure how familiar you are with critically appraising studies, I'll try to walk through what is glaring in the study.
I’m going to preface this with: this isn’t going to hurt you, so if you enjoy using it and you think it helps you, there’s no reason NOT to do it. If that’s good enough for you then that’s fine.
Alright, let’s take a look at the study you linked. First thing is Nicholas DiNubile and Kenneth Blum are both paid consultants (as identified on the pilot study) but there’s no conflict of interests reported in this paper.
Gary Reinl was the one who taught all the participants to use the device. He’s not an author on the paper, but a paid consultant as well (as identified on the pilot study).
Method section:
First study: 43 participants (8 male, 35 female) avg age 61.3, of which 22 used marc pro and 21 did not. Unknown what their injury history is, if they are sedentary, if they’re active, if they resistance train currently or have in the past, if they are allowed to do anything else outside this study, so it’s unknown if the groups are equal, and it’s unknown how the randomization occurred (if it occurred). Why would this be an issue? For example, if there are less resistance trained people in the intervention group, they should have larger gains than those who may train already. Then it would have nothing to do with the device and all about how the groups were chosen.
Trained twice weekly in 60 minute sessions for 10 weeks on a nautilus machine. They did 1 set of 8-12 reps per exercise and resistance increased once they hit 12 reps.
Those in the marc pro group were given marc pros and were to self-administer 1 hour to the calf muscles of both legs 4 days a week for 10 weeks.
Assessments were done first week and last week. Calf strength was measured “by the 3 RM weight load, which was the heaviest resistance that could be performed 3 times with correct technique” and calf muscle fatigue on a 1-9 scale.
Main takeaways from the first study:
At the end of 10 weeks, the marc pro group had a between group difference (from the no marc pro group) of 26.6 lbs for the 3RM calf press. That is pretty decent, but yes, there’s a lot of bias that may be in the article. That stems from who is present during the training, what coaching cues are used if any, who is gathering the data (if they know which participants are in the control group or not, they may be biased non-verbally and/or verbally during the 3RM testing), the fact that there’s one group that received something vs. a group that received nothing, instructions given for the marc pro (“this device is used by many pro athletes, it can help in fatigue and maybe even increase muscle strength"). Not saying that is what was said, but if anything like that was said, that may influence results because now participants are thinking “This is going to help me”
For subjective muscle fatigue there is a between group difference of 0. Both groups had muscle fatigue of 1.8 with a standard deviation of .3 at the end of 10 weeks.
It would’ve been nice to have actual objective markers for recovery, like serum creatine-kinase, IL-6 and CRP, since subjective methods don’t tell us anything about actual objective markers.
These are all reasons why we try to limit this stuff during a study, so we can parcel out “Hey, is this actually helpful to the population I’m working with, or is it nothing better than cupping, ktape, IASTM, dry needling, etc…” all of which we know are useless.
And since the study design is with 60 year-olds, you can’t generalize it to the athletic population, since that population is not tested.
If we were to rate this study using the PEDro scale it’d be a 3/10 which is poor.
Eligibility criteria specified: No (although this isn’t counted on the 0-10 score)
Subjects randomly allocated: No
Allocation concealed: No
Groups similar at baseline regarding prognostic indicators: Unknown
There was blinding of all subjects: No
There was blinding of all therapists who administered the therapy: No/Unknown
There was blinding of all assessors who measured at least one key outcome: No/Unknown
Measures of at least one key outcome were obtained from more than 85% of the subjects allocated to groups: Yes
All subjects for whom the outcome measures were available received the treatment or control conditioned as allocated or ITT: Yes
The results of the between-group statistical comparisons are reported for at least one key outcome: No (within group differences, but not between group).
The study provides both point measures and measures of variability for at least one key outcome: Yes
Going back to their method section, remember that those in the marc pro group were given marc pros and were to self-administer 1 hour to the calf muscles of both legs 4 days a week for 10 weeks. Well, here’s a method section on estim from a study done a few years ago:
The subject was seated with hip and knee flexed to 90° and 60°, respectively. A generator (Compex1, Medicompex, Switzerland) provided bi- directional symmetric rectangular impulses directly to the skin through surface electrodes placed on the left thigh. Three independent channels were employed. They were composed of two poles, one of which was connected to a “stimulating” electrode (5x5 cm) and the other to a “dispersive” electrode (9x5 cm). The 3 stimulating electrodes were placed over the motor points of the vastus medialis, vastus lateralis and rectus femoris of the quadriceps. The dispersive electrodes were placed transversally on the proximal portion of the thigh. Pulse width was 0.25 ms and pulse frequency was 5 Hz. Pulse characteristics (shape, width, amplitude and frequency) were checked previously by means of an oscilloscope. The investigators adjusted the current intensity independently on each channel in order to get an homogenous non-tetanic contraction tolerated by the subject. During the ESR (25 minutes), the current intensity was regularly increased to maintain a visible and palpable muscle contraction in order to reproduce the traditional use conditions of such NMES program. At the end of stimulation, the mean (± SD) current intensity was 47 (± 13), 49 (± 15) and 45 (± 14) mA respectively for the vastus medialis, vastus lateralis and rectus femoris. - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3761726/
You will find nothing like that in any of their studies, making it harder to replicate.
What do we know about other modalities that are similar?
No difference between massage, upper body ergometry, estim, or doing nothing for soreness, MVIC, or peak torque - https://pubmed.ncbi.nlm.nih.gov/7827630/
No difference between active recovery cycling, estim, or doing nothing for quadriceps MVIC and soreness - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3761726/
Evidence is not convincing to support estim for recovery after exercise - https://pubmed.ncbi.nlm.nih.gov/24552796/
“There isn't enough good-quality scientific evidence to say for sure whether TENS is a reliable method of pain relief.” https://www.nhs.uk/conditions/...ve-stimulation-tens/
That is what I meant when I asked if there was anything better currently out there, because this doesn’t tell me anything about athletes and it’s not something I would purchase. Conversely, I wouldn’t slap it out of anyone’s hands, either, unless they were doing it over things that were ACTUALLY helpful, if that makes sense?
Like if someone decided to forgo a proper training program with load management and autoregulation, sleep, nutrition, and instead focused on just using the device, that would not be helpful at all. But if they checked all the boxes and wanted to add that in because they like it, I wouldn’t say no to that, either.
