This article was inspired by research synthesized by the amazing folks (Greg Nuchols and Eric Helms) at MASS (where they review loads of research on lifting) with a focus on application to aerial and circus training.

Traditional circus training is a world unto its own. Body positions, loads, angles, and leverage are unique to many circus disciplines so it’s no surprise that many methods have evolved from generational knowledge. With regards to strength, progressions can often be passed down from coach to student, with little deviation from the program. With regards to circus families, this makes sense, as techniques that work for the older generation are likely to work for the younger, especially if they begin circus training early. However, for those who are introduced to circus later in life, and for those with different backgrounds, it may be helpful to reexamine these methods. 

The accepted ideas for much of circus strength training is to work to failure as well as the idea of always putting the work in (grind grind grind). These ideas can be dangerous considering that many artists practice in the air or are practicing incredibly dynamic movements on the ground. Grinding away when muscles are fatigued isn’t only potentially increasing injury (chronic or acute) risk, but also can diminish gains. Therefore, it may be better to think of circus strength training with regards to perceived exertion. 

According to Greg Nichols, author of Stronger by Science, “Intensity is the primary driver of strength gains, and [I think that] staying further from failure during training helps ensure that subsequent workouts are also high quality.” This study¹ by Schoenfield et al (2017) on powerlifting showed gains among trained lifters in 1RM (1 rep max) strength were greater in higher load (>60% 1RM) with lower rep training, rather than low load (<60% 1RM) and higher reps. This powerlifting study indicates that, indeed, intensity of a workout leads to greater gains. Reading this, we might think that training at or above 60% of our 1RM with fewer reps is the way to train. 

_{Hypertrophy is often defined as an increase in muscle size (thickness/diameter), which is sometimes conflated as being directly correlated to increased maximal strength output, but that is not the case. In general, hypertrophy isn’t going to have a huge relationship to circus and aerial skill success.}

Based on research^{1, 2, 3}, the goal in training would be then be to maximize training intensity, but stay away from training to failure. Again, our goal is to maximize gains while limiting injury risks. Evidence shows² (Davies et al, 2016) that there is no difference between failure and non-failure training in terms of maximal strength gains. However, because “failure” training has some other impacts (like increased muscle damage, decreased motor learning, and increased recovery time – thanks for the update, Eric Helms), failure training for a lot of circus skills work may not be the way to go. That said, “failure training” can have benefits for increasing strength endurance (like holding a reverse meathook), though as always, here’s a study which shows that failure training may not be necessary for increasing endurance if maximal training volume and intensity are equalized.

What about the research that indicates performing a strength training exercise to failure leads to greater gains than a lower intensity?

Research³ by Nobrega and Libardi (2016) has suggested that “failure training” recruits more motor unit activity (the primary contractile unit of muscles), and with more muscle fibers working there should be more muscle adaptation. However, the trick with all of this research is that strength training studies are usually over a short time-frame with a specific type of participant (trained/untrained, adult/youth, et cetera) without always looking at longitudinal rates of adverse events (injuries) in response to type of training analyzed. 

Because circus has a high risk for injury, recruiting more muscle fibers (via training to failure) may not be optimal for all trainees in the long run. For example, training back flags (which takes just about our entire posterior chain) until you can no longer hold them can lead to compensatory patterns (in an already risky position) over time or acute injury.

Training to failure (either through high load or through high reps) may lead to greater gains. But our gains slow down if we get injured. 

Some of the meta-analyses (or studies within them) are looking at untrained subjects when showing the lack of effect for training to failure, and trained subjects when looking at the effect of training to failure. Very few of these studies look at long term changes (a year or more of training) as well as the longitudinal health effects of training to fatigue. 

In one 10-week study⁴ (Martorelli et al, 2017) of active women under 18, resistance training their biceps to failure did not lead to additional gains in max strength, endurance, or muscle size (of the biceps), with impaired force production at faster muscle velocities (for those training to failure). Force production (impaired or improved) at faster velocities has relevance to aerial skills and strength.Though this isn’t studying aerialists, we can extrapolate that perhaps for our younger students, training to failure isn’t necessarily going to lead to better outcomes. 

All this to say, there are arguments for training high intensity for time or load stopping training pre-failure as well as training to failure, and even training at a lower loads (to reduce injury risk). A number of studies indicate relatively similar levels of endurance gained when training high intensity or low intensity, while others reinforce specificity (for example, endurance-based strength training leads to greater endurance, rather than gains in maximal strength).

Keep in mind that in general super beginners will overall benefit from high volume work to build capacity. Intermediate level aerialists will probably benefit from a number of sensible protocols, and only at the highest levels is precision in programming necessary to see increased gains.

The above discussion on different types of training protocols leads to two important concepts: individuality and auto-regulation. 

Individuality is the idea that what works well for your average person in a program, may absolutely 100% not work for a specific person. Beaver et al. did a rad study⁵ of TRAINED lifters (rather than untrained athletes) trying 4 different training programs/workout protocols, and then testing  how much testosterone was produced in their saliva as a response to each protocol (where Tmax indicates higher levels versus Tmin indicates lower levels). The study then matched each participant with their best/worst protocols (based on Tmax/Tmin). These were the 4 different protocols:

1. 3 sets of 5 reps at 85% 1RM with 3 minutes of rest between sets

2. 4 sets of 10 reps at 70% 1RM with 2 minutes of rest between sets

3. 5 sets of 15 reps at 55% of 1RM with 1 minute of rest between sets

4. 4 sets of 5 reps at 40% of 1RM with 3 minutes of rest between sets

The study either put people in a workout group that generated their highest testosterone response or in a workout group that generated their lowest response.  The study matched half the participants with the protocol that produced the highest testosterone response and half the participants with the protocol that produced the lowest T-response, and had them use their respective workout protocol for 3 weeks. They retested 1RM (1-rep maxes) at the end of each 3 week block (as well as whether their acute testosterone responses changed), and then they switched protocols and groups (now half starting with the worst, and half starting with their best). 

Which protocol do you think will have the most success? 

This is a trick question. Different protocols had different success depending on the person. There was an average (group) increase (around 7% over just 3 weeks!) in strength for those using their Tmax exercise protocol, as well as an individual increases. Nearly all participants saw no gains or decreased strength when using their respective individual Tmin exercise protocols. This highlights individuality among trained athletes – what works best for me, might not work best for you and vice versa. 

Most lifters in the study had their best gains in strength (and relative T-response) at 4 sets x 10 reps at 70% of their 1RM, but 2 participants saw strength increases at 4 sets x 5 reps at 40% of their 1RM (and got weaker/no improvement using the protocol above that worked for most other lifters). All this to say: what works really well for most lifters (and we’re extrapolating to aerial strength training) will probably not work well for everyone. While this was a lifting study, the results could definitely translate to circus training.

Remember that each participant was doing a DIFFERENT protocol based on their best/worst acute testosterone response. Don’t get hung up on salivary testosterone measurements as crucial to building a workout plan, but rather (especially if you’re a coach) internalize that there are huge individual differences in terms of response to the same exercise protocol, and what works for one student (or even what works for you) may not be effective for ALL students.

There may be temptation to think, “I must be that unique person who makes more strength gains with a light workout protocol” (or vice versa – the person who has to work REALLY hard to see gains). If you’re a coach, start with what you know works best for MOST people, and then adjust when you have a student who is putting in the work, and isn’t making gains or is even getting weaker. Don’t fall prey to the idea that they are lazy or unmotivated and just need to workout harder, do more reps, or train more frequently – though sometimes that may actually be the case.

What about the thing related to individuality? Here it is – autoregulation!

Autoregulation is the idea of basing our training intensity/load/volume each day based on the person and their physical and emotional state, or individuality (occasionally using metrics like rate of perceived exertion of repetitions in reserve or velocity). In other words, it says that training can and indeed should be customized to daily feedback cues.

Though this has been explored in weightlifting, again, I believe the circus world could benefit from familiarity with it. Just like in any exercise field, some of the notions around strength training in our industry are outdated, are injuring people, or are keeping them from making gains.

This includes the individual’s response to aerial/strength training and other external stimuli like nutrition, sleep, mood, hydration, training volume, hormone cycle, and general socio-emotional/economic stressors.

Just a quick note: the research around hormone cycles impacting training differs from anecdotal experience that I’ve gathered from high level aerialists – again highlighting the potential for individual variability as well as the impact of beliefs/expectations on strength output.

Autoregulation can be a tool to empower aerialists and circus artists (or their coaches) to modify their training based on the above; however, critics of autoregulation, perhaps rightfully, believe that a lot of people don’t know how to (accurately) listen to their bodies due to poorly anchored set points, social pressure, et cetera. Thus, there is the risk that poor autoregulation will lead to people to training TOO hard when they shouldn’t or not training hard enough when they should – rather than using objectively pre-determined metrics like sets/reps and percentage of 1RM (something potentially harder to measure in body-weight training). 

In circus, we especially know that some of us LOVE to go hard (and we feel most productive when we’re out of breath, sore, bruised, et cetera), though on the flip side, we also may have that student who will take every opportunity to do as little as possible (and then maybe sometimes complains about never making progress). In a lot of cases, people who haven’t been life-long athletes don’t do a great job of “training by feel”. Life-long athletes may not do a great job of it either considering our brains aren’t always the best at self-assessment.

Luckily, auto-regulation is not solely subjective training by feel in an effort to respect individuality. Instead, it uses evidence-based subjective questionnaires (like those looked at in this review⁶ by Saw et al., 2016) and other metrics (like the “repetitions left in reserve” metric designed by Mike Tuchscherer discussed shortly). 

The questionnaires used are more consistently accurate in monitoring things like risk for overtraining and overall athlete well-being. Biometric measuring, like using blood markers has been shown (see the meta-analysis) to be less consistent. Heart rate variability assessments, which have been touted by some as THE useful measure for self-assessment and autoregulation, only have limited correlation with overtraining, fatigue, and overall mood compared to tested questionnaires and some other metrics.

*At a week long straps retreat, a few of the students had HRV watches, and those numbers did not always match up to how they felt on day 3 of the retreat just before the rest day. HRV said they were golden, but they were fatigued af. That said, the use of an HRV watch can help someone, who may not be great just yet at listening to their body when they train, get a sense of how their body is doing. They can match their numbers with their subjective feeling – when the numbers and feeling match, start to go by subjective feeling since we know that valid subjective assessment tends to be associated with more markers of well-being. This can help people prevent injury and learn to listen to how for much they should train, rather than grinding out reps until they get to the end of their workout.*

The subjective self-report measures in the study above not-withstanding, for autoregulation, the commonly used methods for determining intensity/load of a workout (outside of HRV assessments) are: 

• RPE (rate of perceived exertion) – using a scale of how HARD something is.
• Velocity of the lift (higher velocity would mean you can increase the weight). This would be like how fast you could do a pushup. If you can explode up from the ground quickly, you could make the pushup harder (which would likely mean you aren’t able to explode up as quickly).
• RPE (repetitions left in reserve)⁷ based on the number of repetitions you believe you could perform before reaching failure within a set. This method is highlighted by Helms et al. 2016, and I first learned of it from this article written by Eric Helms.

RPE (Rate of Perceived Exertion) based on Repetitions in Reserve

Let’s look at RPE based on the number of repetitions left before failure or RPE of reps in reserve⁷ because in circus/aerial, like lifting, the risk of injury is not worth the potential gains of a few extra reps closer to failure when you’re hanging from one arm. 

The general idea is that it is a scale of 1-10, with 1-4 = “very light to light effort” and you could 6 or more repetitions up to 10 = “could not do more reps or load.” I’d argue our goal is to work in the 7-8 range (assuming equivalency of the 70-80% 1RM). The 7-8 RPE (based on reps in reserve) range would mean you believe you could do 3 or 2 more repetitions at the same load. 

A student is working on 1-arm inversions, got good sleep, have been eating well, have low/no stressors, and are feeling well recovered, et cetera), then they would do whichever level of bodyweight aerial progression they can stopping once they perceive they can only do 2-3 more full ROM repetitions of that progression. Since they slept well and feel great, let’s say their max that day is around 6 arm and a half lifts to nutcracker, so they stop before failure at around 3, maybe 4 reps.

The next time they work inversions, they feel like junk, but still aim to hit a 6-8 on the scale (in terms of perceived amount of reps until failure). They feel like junk and think they can only do 4 arm and a half lifts to nutcracker so they stop each set at around 2 reps. This may be significantly lower than their max on a good day, but ideally it keeps them from overtraining or risking acute injury due to trying to hit a training load that their body isn’t ready for that day. 

You might be wondering how to apply this to aerial training. Based on everything discussed above,  consider trying higher load (using different bodyweight progressions depending on your level) aerial strength training, aiming for 3-4 sets of a rep amount stopping 2-3 more repetitions before failure per set. That keeps the relative intensity safe, but high. In other words, the training should be intense, using as much load as the body can handle for 6-8 reps, but should also stop a few reps well before failure. 

Now granted, if doing 4 sets of 70% of your 1RM or of a 7 on the scale (2-3 reps left before failure) of your RPE (rate of perceived exertion based on reps prior to failure) without progress or gains, you can always change it. Just remember, it can be easier to ramp things up slowly (or start at a lower intensity) especially to find out if you’re one of those aerialists that makes gains at 4 sets of 40% of their 1RM than it is to go hard, get injured, and have to recover from injury.

Training at a 7 on the scale of RPE, based on repetitions left in the tank, may reduce injury risk, place yourself in a training protocol that works for most people for strength (and other) gains, and give you the flexibility to adjust your plan based on your life, body, and recovery. That said, there many training protocols that will work for most people, especially those who aren’t close to their maximum potential.

This is not to say that if the conventional ideas and protocols around training load/volume relationships and specificity are working for you (they’re much easier to understand for your average athlete: “I do 3 sets of 5 leg raises”) you should throw them out. But if you’re not making progress, consider looking into making these (or other) adjustments. When training and choosing how to train, keep in mind that your primary goals are to stay injury free, have fun, and make progress (in different levels of priority for different people). Worrying about how to make the MOST optimal progress is almost not worth the mental effort unless you’re plateauing or are a professional athlete who gets paid to train. 

If you’re curious to learn more about customized program creation, private lessons or training, and auto-regulation, feel free to stay tuned on my website (and IG) for more discussions around the science of training!  If you’re looking for more informative and enjoyable writing around the science of training, check out Stronger by Science and the MASS research review.

Thanks to Max March-Steinman, Sadie Brown, and Emma Foster for editing and reviewing my ramblings for readability.

Quick references, but there are way more out there! 

1 – https://pubmed.ncbi.nlm.nih.gov/28834797/

2- https://pubmed.ncbi.nlm.nih.gov/26666744/

3- https://pubmed.ncbi.nlm.nih.gov/28834797/

4- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5505097/

5- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4789708/

6- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4789708/

7- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4961270/

Eccentrics (Negatives) for Safety/Injury Prevention

One of the litmus tests that I use before sending someone on their merry way to begin dynamic movement in a certain pathway is whether or not they can do the eccentric/negative with control.

For example, if you were to have someone leave a front-balance into a beat on trapeze, a good litmus test would be to see that they’re able to a controlled lower from toes to bar (leg raise) into a hang. This is just an example, but if someone’s legs fall immediately into a long hang from a toes to bar, there’s an increased risk that in leaving the bar from a front balance into a swing, that they’re putting heavier load on their shoulders and hands. Or if someone did a slower lower of toes to bar but their grip seemed to slip, it can be an indicator that leaving the bar with momentum might increase their risk of their grip failing. Or if their shoulder blades under or over-rotate/tip/elevate while doing the slow lower, chances are, under a fast movement the less ideal pathway will occur.

Now, this is just an example, but the same general thought process can be applied to teaching and learning a lot of skills. It is up to you as a coach (or autodidact to think ahead to dynamic skills and movements to break down potential failure points where having increased control through the range of motion can protect your joints/muscles/nerves from suffering undue damage (from either acute injury or from loss of coordinated motion to reduce repetitive strain type movements).

Photo by the amazing Ross Kyker

There are definitely ways that this strategy can get tricky to implement, and this is where finding a high level coach can be useful. For example, there are certain movements where giving a watchful eye to someone’s scapular and humeral control during eccentric movements can be useful in noting where the failure points might be for them (as opposed to just watching them move through the pathway with what looks like good form). If someone is doing what looks like a great looking straddle down (slow, controlled, and with good compression), but their humerus is internally rotated, chances are, they may not have adequate control (in the eccentric) in their shoulder complex.

Another benefit of eccentrics is that increased muscle length (as eccentric exercises have been shown to add sarcomeres in series – ie. making the muscles longer) – because we, as movers of our own bodies, want to be strong in as big a range of motion as we can!

I would recommend using eccentrics as a part of your aerial training, both to functionally work on skills that you don’t have the full concentric motion of, and an an injury prevention tool to build control as an exit pathway from static positions, as well as a visible litmus test for injury prevention before practicing a dynamic movement.

If you have any questions on how to use eccentrics as a litmus test for dynamic movement (or on how to use eccentric exercise without as much muscle damage) feel free to PM me (or email me: koz.circ@gmail.com).  Please feel free to respond with comments, thoughts, and questions!

Footnote: Eccentrics have been shown to induce higher levels of muscle damage and inflammation over other types of muscle loading (citation) (and increased muscle damage and inflammation has not been shown to lead to increased levels of strength. However, research has also show that after the first session of maximal eccentric training of a muscle that there is a protective effect for future and following bouts of eccentric exercise (sometimes for up to 6 months) so whether or not you believe that the increased muscle damage is good or bad, it is diminished after that first session, and the benefits of eccentrics (for injury prevention) still outweighs this potential negative (the increased muscle damage). So if you’re worried about training eccentrics, there are ways to mitigate the muscle damage, but I’d still recommend them functionally on many levels.

http://www.lookgreatnaked.com/articles/mechanisms_of_muscle_hypertrophy.pdf – THE MECHANISMS OF MUSCLE HYPERTROPHY AND THEIR APPLICATION TO RESISTANCE TRAINING

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4620252/#B14 – Overview:Physiological and Neural Adaptations to Eccentric Exercise: Mechanisms and Considerations for Training

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4760450/ – Muscle damage and inflammation after eccentric exercise: can the repeated bout effect be removed?

https://www.ncbi.nlm.nih.gov/pubmed/23977721 –  Eccentric exercise-induced delayed-onset muscle soreness and changes in markers of muscle damage and inflammation.

https://pdfs.semanticscholar.org/838d/7c00cc996c30837c753c3ee9dddd845680d1.pdf – Characterization of inflammatory responses to eccentric exercise in humans