September Research Round-Up: Rest Period Edition

Every month, Chris and I write the monthly S&C Research review service. Subscribe, and you will learn about the 50 most important sports science studies published every month, covering strength & conditioning, biomechanics, anatomy & physiology, and sports medicine.

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You can subscribe HERE or just try it by buying a back issue HERE.

In this article, Chris has written a short preview of the September edition, which covers some fascinating new research into rest period duration.

Does rest period duration affect gains in strength during pre-exhaustion training?

The study: The effects of pre-exhaustion, exercise order, and rest intervals in a full-body resistance training intervention, by Fisher, Carlson, Steele, and Smith, in Applied Physiology: Nutrition and Metabolism, 2014 In, this study, my friend James Fisher led a team of researchers to investigate the effects of pre-exhaustion training, which has probably never been studied in a long-term trial before. Although this study is getting a lot of press already for its exploration of pre-exhaustion training, it might escape some people that the researchers actually also looked at rest period duration as well. There were 3 training groups: (1) pre-exhaustion training (single-joint exercises prior to multi-joint exercises) with as little rest as possible, (2) pre-exhaustion training (single-joint exercises prior to multi-joint exercises) with 60-second rest periods, (3) the same exercises in the reverse order (multi-joint exercises prior to single-joint exercises) with 60-second rest periods. By comparing the first two groups, we can see the long-term effects on strength gains of very short and short-to-moderate (60 seconds) inter-set rest period duration. In fact, there was no difference in strength gains in respect of the gains in any of the exercises. Whether different results would have been observed if another group had used an even-longer rest period, however, is unclear.

Practical implication: rest periods don’t make that much difference to strength gains during pre-exhaustion training, so when using this method choosing a length of time for resting between sets can be made based on practical issues, such as length of overall workout, intended volume of training, working in with a training partner, etc.


Does rest period duration affect gains in size?

The study: The effect of inter-set rest intervals on resistance exercise-induced muscle hypertrophy, by Henselmans and Schoenfeld, in Sports Medicine, 2014 In this review, the researchers assessed the effect of rest period duration during resistance-training for hypertrophy. The reviewers explain that although many previous authors have recommended short rest intervals of 30 – 60 seconds for achieving the greatest gains in muscular size, these recommendations are not supported by the findings of the limited number of long-term trials, which show either no effect or a benefit of longer rest period durations. Interestingly, the reviewers raise an important concern relating to short rest periods. If short rest periods are not directly beneficial, then whether they are used is largely a matter of personal preference or workout duration, unless they have any adverse effects. In fact, the reviewers did note some safety concerns. Previous studies have found that when using very short rest period durations, neuromuscular postural control and proprioception are negatively impacted by fatigue. Thus, short rest period durations are a higher-risk strategy, particularly when using multi-joint, free-weight exercises with heavy loads. So the use of short rest periods does not seem to have a good risk-reward ratio where the primary goal is hypertrophy. Whether the same adverse effects would be observed in machine-based workouts, however, is unclear.

Practical implication: rest periods don’t make that much difference to gains in muscular size so for bodybuilders and physique athletes, choosing a length of time for resting between sets can be made based on practical issues, such as relative safety, length of overall workout, intended volume of training, working in with a training partner, etc.

Arnold and Dave

Do 1-minute or 2-minute rest periods lead to significantly different training volumes?

The study: Comparison of repetition number between uni-joint and multi-joint exercises with 1-min and 2-min rest intervals, by Dias, De Matos, Filho, Moreira, Hickner, Cardozo, Alves, Reis, and Aidar, in Journal of Exercise Physiology Online, 2014 In this study, the researchers assessed whether rest period duration would affect the number of repetitions performed in an acute resistance-training intervention using both single and multi-joint exercises in resistance-trained males. Unsurprisingly, they found that work done was significantly greater for the 2-minute rest period duration condition in comparison with the 1-minute rest period duration condition for both the single and multi-joint exercises. The researchers also noted some other important findings. They observed that neither the 1-minute nor the 2-minute rest period durations were sufficient for full recovery between sets, and they found that single- and multi-joint exercises display different training workloads with the same relative load with the same rest period durations. Specifically, they noted that the multi-joint exercises displayed larger reductions in the number of repetitions performed during repeated sets with shorter rest periods. Therefore, longer rest periods may be required for multi-joint exercises than for single-joint exercises in order for the same workload to be performed.

Practical implication: rest periods may need to be longer for multi-joint exercises than for single-joint exercises, in order to maintain high training volume. This may suggest that advanced bodybuilders may gain from using machines in their training, as it could allow them to perform more work in less time.


How do these studies affect our programming of rest periods?

These three studies contain important practical implications for programming rest periods during resistance-training, as follows:

  • Pre-exhaustion training doesn’t benefit from extremely short rests;
  • Rest period duration doesn’t make much difference to hypertrophy;
  • More rest is needed for multi-joint exercises than for single-joint exercises.

These study results go to show that there is more to setting a rest period than long rest periods for strength and shorter rest periods for hypertrophy. Simple is usually better than overly complex but sometimes things just are that little bit more complex than we might want them to be.

Although complexity can be a distraction when writing programs, it certainly keeps the results of new studies interesting. Bret and I like to think we know sports science pretty well, so for fun, we’ll often guess an outcome before we read a study. We base our guesses on what other researchers have found and what know about the underlying mechanisms. But since the human body is so highly complex and unpredictable, we often guess wrong!

This is a recommended resource, so don’t miss out! Subscribe HERE or buy a back issue HERE.

strength and conditioning research

Who Are the Experts?

I sometimes find it amusing when I receive questions from my readers and I can tell that they assume that I’m an expert an all things musculoskeletal related. Now, due to the fact that I scour through up to 100 journals per month in fulfillment of my responsibilities for Strength & Conditioning Research I do consider myself to be a bit of a renaissance man in the fitness field. However, delving into the research like this teaches you just how clueless you are with regards to many aspects of strength training and conditioning, biomechanics, anatomy, physiology, physical therapy, and research methods.

Realizing Just How Much You Don’t Know

My intern Andrew Vigotsky is one of the smartest guys I know. We meet several times per week and discuss various studies and aspects of science. Quite often we just don’t have the expertise to adequately understand a particular study, so we speculate and hypothesize, but in the end we realize that we’d need to contact the author, read more research, and conduct our own experiments in order to possess a full grasp. The problem is, nobody has this much time to devote to researching. We have to sleep, have social lives, and make money, so we can’t just spend our days in the lab reading and experimenting. That’s why the most intelligent guys in sports science have sufficient experience. It takes considerable time to build up an impressive base of knowledge. I’ve only been critically reading research for around five years. Sure, I read research prior to this, but I never scrutinized it and strived to fully understand it. There are plenty of folks who have been reading, publishing, and peer-reviewing research for several decades.

Nevertheless, there is one topic that I am highly confident in my knowledge, and that’s the gluteus maximus. With every other subject, there’s someone else out there who is much smarter than me. Nevertheless, there are so many aspects to every topic that even the top exert will require consultation with various colleagues, and this includes the gluteus maximus.

For example, a researcher by the name of Gunnar Nemeth and another by the name of Teddy Worrell pioneered some of the hip and gluteus maximus research that is critical for our current understanding of the glutes, and I am building on their foundation. And even though I’m an expert on glutes, I still need much help. For example, I’ve reached out to research professors Silvia Blemker and Sam Ward in the past to reinforce my knowledge of hip extension moment arms, gluteus maximus pennation angles and physiological cross sectional area calculations. I’ve reached out to Stu McGill to help me understand inverse dynamics and modeling, Brad Schoenfeld to help me understand hypertrophy physiology, Matt Brughelli and Jurdan Mendiguchia to help me better understand hamstrings biomechanics and shifting optimal lengths of muscle, JB Morin to help me better understand sprinting forces and biomechanics, Jason Lake to help me better understand biomechanics with regards to the force plate, and Bryan Chung to help me better understand research methods. When I have an EMG related question, I seek help from Noraxon, the company that sold me my Myotrace.

Realizing Just How Much Others Don’t Know

What I’m trying to portray is that we need to have a large network of individuals to learn from in a wide variety of fields. Last year I posted an article on my site showing an illustrated guide to what a PhD is (HERE). We can only be experts in a narrow field, and nobody can know it all – not even close. Albert Einstein, Richard Feynman, and Stephen Hawking were all absolutely clueless about thousands of important topics. In this day and age, each of us are very intelligent in a few areas, moderately intelligent in a broad range of areas, and utterly ignorant in a wide variety of areas.


I’ve been very lucky in the past several years to have picked the brains of some of the most knowledgeable people on the planet. I can’t tell you how many emails I’ve shot off to researchers after reading through an article (probably 50% of the time I get a response, and 50% of the time I get ignored). I’ve called researchers on the phone, made special trips to different states (even different countries) just to get a chance to have a discussion with someone I highly respect about a particular topic that’s eating me alive. Consistently, with just about every expert I’ve met, I’m blown away by their knowledge in a specific area, but at the same time, slightly amazed at how little they know about other areas. But it makes perfect sense – a professor studying muscle architecture or neurobiology most likely won’t have the time or passion to put in the same number of hours studying strength training or program design (or other topics that aren’t directly related to their specific interests).

Some experts tend to overestimate their knowledge and assume that just because they’re highly intelligent and knowledgeable in one area, it makes them an expert in another area, while other experts tend to be extremely humble and cautious with their claims pertaining to other areas. It is our job to glean the valuable bits of knowledge that the expert possesses while being able to discern between what to value and what to disregard.

I recall meeting with Michael McGuigan, a New Zealand research professor who specializes in power training. I was very excited about our meeting. I had prepared a list of questions to ask him, and his reply to almost all of them was, “I don’t know.” After the meeting, I had mixed feelings. I realized that 1) I’m constantly seeking out experts to teach me what I want to learn, but often this knowledge doesn’t exist, and 2) My quest for truth is going to require a lot of patience and decades of learning. What I can tell you is that my respect for Michael went through the roof. He didn’t try to pretend he knew the answer to all my questions, he just gave it to me straight. We still had a very productive meeting, discussing current research and theory pertaining to power development, but many times, the burning questions we have in our brains don’t have ample research surrounding them to provide us with sufficient fodder for an answer.

Experts in the Blogosphere

So who are the experts? There are thousands, but you have to find them. In the blogosphere, there are several individuals whom I highly trust and respect. For example, I believe that Chris Beardsley has the best sports science blog on the web. Brad Schoenfeld is the world’s expert in muscle hypertrophy as far as I’m concerned. Alan Aragon has a kickass research review and is the most intelligent individual I’ve ever met in areas pertaining to body composition and sports nutrition. Menno Henselmans is another guy I highly respect. I see a great future for The Strength GuysGreg Nuckols, and Armi LeggeLayne Norton and Eric Helms are highly intelligent and they walk the walk with regards to natural bodybuilding and powerlifting. Tom Purvis‘s YouTube channel pertaining to biomechanics is incredible. Bryan Chung understands research methods better than just about anyone out there. I tend to be biased towards bloggers who regularly publish research. Since publishing requires so much of a time commitment but doesn’t involve financial reward, this shows a lot about the person’s intent and values.

Menno Henselmans

Menno Henselmans

But here’s the deal. Most of the worlds experts are not blogging. Blogging and social media require a very large time commitment. A top expert doesn’t always have the time or energy to dedicate toward his online popularity or reach, especially when the expert has teaching/lecturing, speaking/presenting, conference attendance, grading, lesson planning, researching, publishing, and committee responsibilities.

Expert Research Professors 

Across the world, there are numerous expert research professors. These folks have been trained to understand research, the scientific method, and statistics. They spend their days looking into past research, experimenting, and trying to think up new study designs in order to advance our knowledge pertaining to their area of expertise. They typically go unnoticed and unthanked in the field, though their contribution is invaluable.

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Are these the go-to guys if you want to improve your powerlifting total or learn about program design for team sports? Not always. If you want to learn about powerlifting (or sprinting, or any sport for that matter), you’re going to have to immerse yourself in the sport and listen to a wide range of powerlifters (or track & field coaches, or other coaches from the sport you’re studying). But studying the science of strength training can never hurt you. Research professors are credible because they tend to have more integrity, they tend to be more cautious with their claims, they tend to be aware of the limitations of their data, and they tend to be committed to scientific advancement. Plus they’d be ridiculed if they consistently touted pseudoscience.

Below are some of the top experts in various fields related to fitness. Keep in mind that there are thousands more out there, and that with some of the fields, I’m not well-versed enough to know who the top experts are. There are undoubtedly numerous individuals who belong on this list, but I forgot about them or simply don’t yet know of them. The list is not in any order, and if the individual has a Twitter handle, I linked it.

Strength Training, Power Development, and Biomechanics

Jason Lake

Naoki Kawamori

Justin Keough

Jacob Wilson

Mike McGuigan

Rob Newton

Greg Haff

Chris Beardsley

Paul Swinton

Robert Lockie

Eduardo Sáez de Villarreal

David Behm

Loren Chiu

John Cronin

Anthony Blazevich

William Kraemer

Keijo Hakkinen

Mike Stone

Muscle Hypertrophy, Sports Nutrition, and Body Composition

Brad Schoenfeld

Stu Phillips

Alan Aragon

James Krieger

Jose Antonio

Per Aagaard

Sprint Running, Running and Gait

JB Morin

Neil Bezodis

Ian Bezodis

Rodger Kram

Greg Lehman

Anthony Schache

Marcus Pandy

Matt Brughelli

Jurdan Mendiguchia

Tim Dorn


Darryl Thalen

Elizabeth Chumanov

Bryan Heidersheit

Carl Askling

Matt Brughelli

Jurdan Mendiguchia

Anthony Schache

David Opar


Maarten Bobbert

The Nervous System and EMG

Roger Enoka

Carlo DeLuca

Eccentric Resistance Training

Ken Nosaka

Muscle Architecture, Muscle Physiology, Muscle Mechanics

Sam Ward

Richard Lieber

Silvia Blemker

Henk Granzier

Walter Herzog

Scott Delp

Sports Conditioning

Martin Buchheit

Connective Tissue Adaptations

Michael Kjaer

Pain & Physical Therapy

Jason Silvernail

Kieran O’Sullivan

Lorimer Moseley

David Butler

Sports Science Statistics

Will Hopkins

Spinal Biomechanics

Stu McGill

Knee Injury Biomechanics

Chris Powers

Timothy Hewett


So there you have it. My current list of favorite experts. This article is my way of giving back to those who passionately pursue their field of study. If you have similar interests as me (sports science, biomechanics, sprinting, power, strength & conditioning), then I recommend that you start following these individuals and familiarizing yourself with their research and beliefs. Wise individuals rely upon trusted sources to keep them informed in areas they don’t have time to research and investigate. Unfortunately, most people never do enough investigation to be able to discern between pseudoscientists, quacks, people with an agenda, snake oil salesmen, and true scientists.

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How to Get the Bar Into Proper Position During Hip Thrusts

On my Instagram page, I’ve been receiving a lot of questions from women asking how to get the bar into proper position during the hip thrust. I therefore decided to film a quick video on the topic, detailing the various methods. The video shows:

  • How to get the bar into proper position when using > 135 lbs (easy)
  • How to get the bar into proper position with bumper plates (easy)
  • How to get the bar into proper position with smaller plates (complicated, but doable)
  • How to get into proper position with a tall bench (complicated, but doable)

And what if you have giant thighs and struggle to roll the bar over your legs and onto your hips? Click HERE to see a solution for that problem.

Ladies, within a couple of months you should be hip thrusting at least 135 lbs for reps. When you reach this milestone, hip thrusting becomes much more comfortable.


What Are the Best Glute Exercises?

Hi Bret, what are the best glute exercises that I should be doing? Thanks, Cindy

This is a question that I receive very often – everybody wants to know what the best glute exercises are. This question is difficult to answer. First of all, in order to be confident, I’d need for there to exist approximately twenty high-quality training studies for me to examine – longitudinal studies that compared the gluteal hypertrophic gains between various exercises, using different combinations of glute exercises, and using different types of subjects (genders, training age, etc.).

This research does not exist. In fact, there is only one training study to my knowledge that measured gluteus maximus hypertrophy – it was a Russian study that examined the lying machine squat exercise. At this point in time, we don’t have any RCT’s to reference in order to help us answer the question. Therefore, we must go down the line in terms of the hierarchy of knowledge and examine acute studies (mechanistic research), pilot data, anecdotal data, and bro-science.

manly glutes

Second, the best exercise for one person might not be the best exercise for another person. For example, if a particular exercise consistently causes pain or injury, it’s not worth doing, no matter how popular or trendy the exercise is. Anatomy plays a large role in determining exercise tolerance, and not every hip is designed to full squat heavy, not every spine is designed to deadlift heavy, and some lifters don’t tolerate the hip thrust very well. Moreover, some lifters don’t feel popular exercises working their glutes very well no matter how hard the concentrate and focus on using the glutes – this applies to squats, deadlifts, hip thrusts, and back extensions.

Training age must be factored in too – a beginner needs to master the box squat, hip hinge, and glute bridge (and also the goblet squat) before adding more load. Moreover, logistics must be taken into consideration. Three of my favorite glute exercises are the band hip thrust, pendulum quadruped hip extension, and horizontal back extension, but most lifters don’t have access to a Hip Thruster, a reverse hyper, and a glute ham developer.

Ask the vast majority of lifters what the best glute exercise is and they’ll likely reply with the squat. Some might say the deadlift, others the lunge, and most of my fans would say the hip thrust. In fact, around 60% of my readers feel that the hip thrust (40%) or barbell glute bridge (19%) is the best glute exercise (see HERE for the results to a poll), with the remaining 40% coming from the squat (8%), deadlift (7%), Bulgarian split squat (6%), kettlebell swing (5%), single leg RDL (4%), lunge (4%), single leg hip thrust (3%), and back extension (3%). I’m sure if you polled primarily Olympic lifters or powerlifters, they’d reply with the squat, but I’d argue that most of these lifters don’t have ample experience with the hip thrust and they’re goals are centered around strength performance and not the hypertrophy of the glutes.

So how do we know what’s best? The answer is, we don’t. The research just isn’t there yet. We can speculate, but we can’t be certain. During my lifetime, I hope to compile a lot of this research and help us hone in on optimal glute training practices over time. In the meantime, we can utilize various tools to help us answer these questions. For example, we can look at electromyography (EMG) data. EMG looks at muscle activation. But there’s more to the hypertrophic picture than activation. While activation broadly mirrors active muscle force, especially during isometric contractions, it gets skewed when dealing with dynamic movements and under fatigue. While EMG is a good tool for estimating mechanical tension, there are three primary mechanisms of muscular hypertrophy – mechanical tension, metabolic stress, and muscle damage (see HERE for a comprehensive article on this topic).

An exercise can have fairly low activation but move through a considerable stretch and produce a good amount of muscle damage. Muscle damage is more related to strain than activation. Similarly, an exercise can have moderate activation, but if it’s constant and doesn’t let up, then it can produce high levels of metabolic stress.

Nevertheless, an exercise that exhibits very high levels of muscle activation will be well-suited for all three mechanisms of hypertrophy, you just have to tinker around with the manner of execution. For example, let’s consider the hip thrust. Perform 4 sets of 6 reps with a brief isometric pause at the top and you’ll get high levels of mechanical tension. Perform 3 sets of 15 reps with no rest in between reps (constant tension – not touching the bar down to the floor), only waiting 60 seconds in between sets, and you’ll get high levels of metabolic stress. Perform 4 sets of 8 reps with an emphasis on the eccentric component (4-sec lowering count), using a higher bench so the hips move through a greater ROM, and you’ll get decent levels of muscle damage.

Hip Thrust

Now, I’d argue that different exercises should be used to target the different mechanisms of hypertrophy. For example, moderate to heavy hip thrusts for mechanical tension, high rep band hip thrusts or back extensions for metabolic stress, and walking lunges or Bulgarian split squats for muscle damage. This is why the best glute building programs involve sufficient variety. Moreover, some folks might have a particular physiology that makes them respond better to certain types of stimuli (for example, the lifters whose butts blow up from high rep hip thrusts and back extensions might respond better to metabolic stress, whereas the lifters whose butts grow substantially from squats and lunges might respond better to muscle damage), but I digress…

For the past few months, I’ve been collecting extensive EMG data for my PhD thesis. I’ve tested some very strong and fit women. In fact, this year alone, I’ve examined 10 powerlifters, 2 Olympic lifters, and 8 bikini competitors. While my thesis primarily examines the squat and the hip thrust exercises, I’ve also compiled a ton of data on other glute exercises.

I’ve looked at different types of back extensions – arched back, neutral, roundback, bodyweight, dumbbell, and band. I’ve looked at kb swings, kb deadlifts, Bulgarian split squats, and pendulum quadruped hip extensions. I’ve examined several types of squats (full, parallel, front, goblet) and hip thrusts (barbell, American, band). I’ve looked at different lateral band movements, and I’ve even looked at various combined movements (for example, banded goblet squats).

Band Goblet

And, I’ve looked at upper and lower glute activity during these movements. While I’m not allowed to release the data just yet as I intend to publish it, I want my readers to know a few things:

  1. Hip thrusts kick ass for upper and lower glutes
  2. Back extensions kick ass for upper and lower glutes
  3. Pendulum quadruped hip extensions kick ass for upper and lower glutes

In future studies, I would actually like to pit the hip thrust, back extension, and pendulum quadruped hip extension against each other with equal relative loading with advanced subjects. It would be very close, but based on what I’m seeing, the hip thrust would probably be best for mean glute activation, but I suspect that the back extension might elicit the greatest peak upper glute activity and the pendulum quadruped hip extension might elicit the greatest peak lower glute activity.

At any rate, here is my advice in terms of best exercises for glute training:

  1. Variety is ideal, so don’t just rely on one exercise for glute building. Tinker around and figure out the variations of each movement pattern that suit your body best – everyone is unique.
  2. Make sure you’re regularly performing at least one type of hip thrust movement (barbell hip thrust, barbell glute bridge, band hip thrust, American hip thrust, single leg hip thrust)
  3. Make sure you’re regularly performing a back extension movement (bodyweight for high reps, band or dumbbell for medium reps, single leg, 45 degree or horizontal)
  4. Make sure you’re performing a couple of squatting movements (bilateral or unilateral) that feel right for you. This can include goblet squats, front squats, back squats, box squats, lunges, Bulgarian split squats, step ups, or pistols.
  5. Make sure you’re regularly performing a deadlifting movement that feels right for you. This can include kettlebell deadlifts, American deadlifts, conventional deadlifts, sumo deadlifts, trap bar deadlifts, block pulls, deficit deadlifts, or single leg RDLs.
  6. When possible, try to add in an open chain hip extension movement (pendulum quadruped hip extension is best, but many gyms have machines that allow for this – HERE is a lady doing kickbacks with the leg curl machine, HERE is a lady doing kickbacks with the smith machine, and HERE, HERE, HERE, and HERE are various butt machines. If you find one that feels right, then go really hard on these and make them a staple movement and go for progressive overload over time. If you can’t find a variation that feels right (you don’t feel the glutes working hard), then don’t do them and don’t sweat it. The 4-way hip machine can work well, as seen HERE. They can also be done with a cable column (HERE), bands (HERE) and ankle weights (HERE) fairly effectively, but in this case, I would do them at the end of a workout for high reps. The pendulum underneath the reverse hyper is best, but again, very few people have access to this machine.

I hope you’ve enjoyed the article and have gained some insight as to what glute exercises are best for building a solid booty. Train glutes a few times per week for best results, and make sure you’re getting stronger over time.