Nicholas Rolnick, The Human Performance Mechanic

07/29/2025

🔬 Does Having A Enhance Outcomes Associated with ?

A new 2025 RCT by Gavanda et al. compared the outcomes of supervised (in-person), app-guided, and self-directed (PDF) resistance training over 10 weeks in trained men and women (n = 79). Each group performed the same full-body training program 3x/week, differing only in the level of guidance and feedback.

📈 Key Findings:

Supervised training (SUP) led to the greatest gains in squat strength (+26.6 kg), fat-free mass (+1.4 kg), and well-being (+15.7 pts on WHO-5).

All groups improved bench press 1RM, but only the supervised group showed significantly superior squat improvements—highlighting the value of real-time technical feedback in complex, multi-joint lifts.

Adherence rates were highest in SUP (88%), compared to APP (81%) and PDF (52%).

Supervision satisfaction (S-SRQ) was also significantly higher in SUP vs APP.

Fat mass increased slightly in the APP group, possibly due to lack of nutritional control and/or compensatory eating.

💡 Implications:
Direct supervision from a enhances , neuromuscular adaptations, psychological well-being, and accountability—especially in technically demanding exercises. While app-based training showed promise for accessibility and moderate gains, it lacked the effectiveness of live coaching - which can be attributed to possibly many reasons, but most likely you want to be a beast in person and not embarass yourself. That’s motivation enough.

📱 Realistically, hybrid models combining digital platforms with periodic human feedback may offer scalable alternatives where consistent in-person coaching is not feasible. Thoughts?

📚 Source: Gavanda et al., J Strength Cond Res, 2025.

06/30/2025

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04/23/2025

Thanks to for the trust in educating the future of our profession in . The trust is invaluable. It means being able to quite literally change clinical practice. It means getting more clinicians familiar with and the importance of muscle . It means making a difference beyond 1-1 patient interactions.

Can’t put a 💰 on influence. I don’t take that for granted and hope to continue to live through example.

04/21/2025

Aerobic exercise has been shown to induce muscle hypertrophy when combined with blood flow restriction (BFR).

That alone is surprising.

Even more perplexing?

Studies like Kim et al. (2015) show no significant differences in muscle activation (EMG) between aerobic BFR and non-BFR conditions whereas Kilgas et al. (2022) showed some pressure-dependent reduction (80% LOP > 60% LOP) in post-exercise maximal voluntary isometric contraction but no loss in high-intensity or low intensity exercise without BFR.

So what gives?

Shown above is a conceptual model of motor unit recruitment that may help explain this paradox.

Surface EMG reflects the total activity of motor units near the electrode—but it doesn’t tell us:

Which fibers are firing

How fatigued they are

Or whether higher-threshold motor units are being pulled in over time

When BFR is added, metabolic stress and local hypoxia rise. This accelerates fatigue in already-recruited fibers, which slows contraction speed and increases mechanical tension—two key hypertrophy signals.

Even if EMG readings appear unchanged, the internal environment is dramatically different.

🧾 A few studies showing hypertrophy with aerobic BFR:

Abe et al. (2006, 2010) – Walking/cycling protocols → +5–8% muscle CSA

Chen et al. (2022) – Running with BFR → +3.7% thigh mass

Clarkson et al. (2017) – Older adults gained size and strength with BFR walking

Low-intensity aerobic BFR likely recruits higher-threshold motor units earlier than standard cardio and to a much less degree than is likely with resistance exercise.

Understanding the force-velocity relationship, motor unit recruitment differences between low- and high-load exercise, as well as other adjunctive markers that may be associated with a heightened physiological environment that may accelerate fatigue accumulation may help inform the hypertrophic potential of aerobic exercise with BFR.

PS: These are part of a long-form article that will be released on my patreon.

04/20/2025

Happy Easter and a reminder we have $20 off plus free shipping on our revolution 2.0 through tonight using code EASTER…sportgrips.com. Now with this thought experiment.

Minimizing fatigue and optimizing motor unit recruitment is essential for maximizing muscle .

This chart shows a hypothetical model of muscle hypertrophy comparing low-load (~90% motor unit recruitment) and high-load (~100%) resistance training over a 2-year span.

Up to 26 weeks, gains appear nearly identical — the low-load group achieves ~95% of the growth seen in the high-load group. Statistically, there’s no significant difference at this point (p = 0.34, Cohen’s d = 0.21). For anyone training recreationally or in a rehab setting, this might seem like good news.

But as training continues, the compounding advantage of full motor unit recruitment with heavy loading starts to show. By week 52, the difference becomes significant (p = 0.005, d = 0.74), and by week 104, it’s even more pronounced (p < 0.001, d = 0.95). This reflects the accumulating benefits of maximizing tension and mechanical load over time.

Assumptions in this model include: – Equal training frequency and effort (sets to failure or near-failure in both groups)
– Trained male participants with no baseline group differences
– Growth potential in low-load group capped at ~90% due to partial motor unit recruitment
– Nonlinear hypertrophy trajectory over time
– Muscle growth measured via CSA or thickness at multiple intervals

Bottom line: while low-load training can work well in the short term, especially when taken close to failure, it’s unlikely to match high-load training over the long haul—especially when the goal is maximizing hypertrophy.

If you’re in this for years, not weeks, that last 10% matters and is something we probably don’t get real clarity on in 99% of the durations of the studies.

helped me out with the illustration.

04/19/2025

Proximity to failure is crucial for low- but not high-load exercise. This paper is one of my favorites that help us with our model of hypertrophy. Here’s what was done.

🧪 Protocol Overview

Study Title: Muscle Failure Promotes Greater Muscle Hypertrophy in Low-Load but Not in High-Load Resistance Training (Lasevicius et al., 2022)

🔍 Design:

Participants: 25 untrained men, each leg assigned to different protocols

Duration: 8 weeks, 2x/week (16 total sessions)

Exercise: Unilateral knee extensions

Conditions (volume equated):

HL-RF: High load (80% 1RM), to failure (~12 reps/set)

HL-RNF: High load (80% 1RM), not to failure (~6–7 reps/set, more sets)

LL-RF: Low load (30% 1RM), to failure (~34 reps/set)

LL-RNF: Low load (30% 1RM), not to failure (~20 reps/set, more sets)

📏 Outcomes:

Quadriceps cross-sectional area (CSA) via MRI

1RM strength for unilateral leg extension

RPE (sessional rating of perceived exertion)

📈 Key Findings on Hypertrophy

✅ Hypertrophy Results:

Significant CSA gains were observed in:

HL-RF: +8.1%

HL-RNF: +7.7%

LL-RF: +7.8%

No significant hypertrophy in LL-RNF (+2.8%, not significant)

🔑 Interpretation:

Proximity to failure is essential for hypertrophy when using low loads. LL-RF was the only low-load protocol that triggered significant muscle growth.

High-load training to failure vs. not to failure made no difference in hypertrophy—both groups saw nearly identical gains.

Volume alone (when not training close to failure) is insufficient for hypertrophy at low loads.

Last note: we know that in untrained participants, the window for eliciting hypertrophy is much wider than untrained participants. Our precision to produce a hypertrophic stimulus MUST be greater during low-load exercise rather than high-load exercise. This means we should be aiming for sets with high effort levels during low-load exercise but not necessarily in high-load exercise. This study used 60% of the volume. Sieljacks (2018) (PMID 30475424) showed similar growth at 75% of the reps to failure in low load exercise, 15% more per set repetition volume than this study did...so as I said, the window is narrower in low-load exercise.

PMID: 31895290

03/09/2025

Here’s the conclusion from my systematic review on whether the addition of improves the muscular outcomes associated with high load . In this article, I unpack the 10 studies published so far that can inform our decision on whether is likely to be a net positive when added to higher resistance exercise loads.

Does this kind of stuff interest you? I’m launching a community where I will post exclusive articles on , , and that will inform the utility of BFR. If you’re looking to get cutting edge information from a leader in the space, you have to check out this group. The first 50 founding members will get discounted access FOR LIFE ($10/month) and after the first 50, price will be $17/month. Post SKOOL below to get more info!

Housed within this community will also be BFR cuff reviews, research summaries etc. as well as longer form articles and of course, a forum for passionate BFR providers can interact with each other on a daily basis. It’s my way of being able to provide insane value but allow me to budget time in my schedule to produce consistent content.

02/20/2025

As a who happens to be a and well versed in the nuances of and , I approach my training philosophy with clients in a tiered approach I envision as something like “Lifting 101” to “Lifting 301” to reflect the added complexities that can be layered onto an intelligent training program. These tiers allow me as a provider to emphasize certain aspects of the exercise performance based upon the experience (and goals) of the client. For example, here’s what each level could be positioned to the client doing a bilateral leg extension exercise: You may find me using questions/statements like:

Lifting 101 - “I want you to lift as many repetitions as possible” (set failure and begin recognizing role of effort and getting comfortable being uncomfortable)
Lifting 201 - “How many more repetitions could you do before complete failure?” (assessing increased role of RIR and relativizing it to failure)
Lifting 301 - “As you get towards the end of the set, kick on the accelerator and be as explosive as possible. Pay attention to your torso as additional fatigue will begin to aid in compensation to shorten the range.” (Living in discomfort to maximize muscle fiber recruitment while paying attention to compensations to maximize stress to target tissue)

These levels help me contextualize and layer in more and more focus as training progresses.

What are your thoughts?

02/01/2025

No this ain't , this is ! Poor in your has been linked with a host of things including:

1️⃣ Increased Mortality Risk:
Poor grip strength is a strong predictor of all-cause mortality, highlighting its importance as a marker of overall health. (Cooper et al., 2010 - "Objectively measured physical capability levels and mortality: Systematic review and meta-analysis")

2️⃣ Cardiovascular Disease:
Weak grip strength is associated with higher risks of heart attacks, strokes, and other cardiovascular outcomes. (Celis-Morales et al., 2018 - "Associations of grip strength with cardiovascular, respiratory, and cancer outcomes and all-cause mortality")

3️⃣ Cognitive Decline:
Reduced grip strength is linked to a higher risk of Alzheimer’s disease and faster rates of cognitive decline. (Boyle et al., 2009 - "Association of muscle strength with the risk of Alzheimer disease and the rate of cognitive decline")

4️⃣ Functional Decline in Older Adults:
Grip strength predicts future physical function, including the ability to perform daily activities and maintain independence. (Bohannon, 2008 - "Hand-grip dynamometry predicts future outcomes in aging adults")

5️⃣ Poor Bone Health:
Weak grip strength is a biomarker for frailty and reduced bone density, increasing the risk of osteoporosis and fractures. (Carson & Lee, 2022 - "Reduced grip strength as a biomarker of frailty and osteoporosis in aging adults")

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12/11/2024

Locked and loaded recently with that same determination for getting through an intense session.

Launched which has been months and months and months of work. Finishing two major papers in and getting ready for the holidays!

11/18/2024

The study aimed to compare the effects of (RT) with “final” partial range of motion (pROM) versus full range of motion (fROM) on muscle and in “trained” participants over 6 weeks. Existing evidence suggested that fROM generally leads to superior muscle hypertrophy and strength compared to pROM (performed in the shortened position 0-45/50 deg). However, studies indicated that training at longer muscle lengths might produce greater hypertrophy, while the potential benefits of final pROM remained underexplored. This study focused on filling this gap, particularly in trained individuals.

Methodology

Design: Within-subject experimental design.
Intervention Exercises: Scott bench curls (targeting elbow flexors 135-50 flex) and seated leg extensions (0-45 flex) (targeting knee extensors).
Protocol: Three sets of 12 repetitions at 60% 1-RM, three times per week for six weeks.
Randomized assignment: One limb performed final pROM, while the contralateral limb performed fROM.
Muscle Hypertrophy Assessment:
Ultrasound was used to measure muscle thickness at the following anatomical sites:
Elbow flexors: 60% of the distance between the acromion process of the scapula and the lateral epicondyle of the humerus.
Knee extensors: 50% of the distance between the greater trochanter and the lateral femoral condyle.
Measurements were taken pre- and post-intervention with participants at rest to ensure consistency.
Strength Assessment: 1-repetition maximum (1-RM) tests conducted for each exercise using the same ROM trained during the intervention.
Statistical Analysis: ANCOVA was applied to account for interlimb differences, with effect sizes reported.
Outcome Measures

Muscle hypertrophy of the elbow flexors and knee extensors, assessed via ultrasound.
Strength, determined by 1-RM tests for scott bench curls and seated leg extensions.

Continued in caption…

10/27/2024

Another one of my projects just published in Journal of Sports Sciences. Here is yet another example of the impact of device features on BFR responses. Here we showed that autoregulation was actually SLIGHTLY more perceptually demanding than non-autoregulated cuff condition without having any impact on exercise performance nor central stiffness. Therefore, contrary to our lower body investigation that showed no impact on any of the above, with upper body autoreg using the delfi, it is probably more uncomfortable. This is definitely something I can attest to personally. Nonetheless, one more piece of the puzzle.

Thanks to my coauthors for another amazing project. We have WAY more cooking. This is just too much fun to stop! ;)