[jwi]

tl;dr
Repeaters is largely an aerobic exercise. Aerobically underdeveloped, or very explosive, climbers are likely to benefit.


"Repeaters" is a shorthand for protocols like 4 x 6 x [7s deadhang @ load ] ; r = 3s, R=3-5 min. That is 6 sets of 1 hang of 7 seconds, with 3s rest between the sets and 3-5 min rest between the blocks, where each block might represent a different hold type or repeated efforts on the same hold, but with increased fatigue.

I am far from sure who coined the term, but I first saw it in the pamphlet from Beastmaker (https://www.beastmaker.co.uk/pages/training) where the load varies between the blocks with hold-type.

The Andersson's brothers have prescribed a very similar protocol where each hold type is used 4 times but the load varies so that the first set is a warm-up, and the next 3 blocks uses a weight so that the effort level is above 100% (that is failure is ensured on the last block). They also prescribe 3-7 superblocks with different hold type, so in standard notation 3-7 x 4 x 6 x [7s deadhang @ load ] ; r = 3s, R=3 min, RR=?min. (I don't have their book, so this is second hand info)

More or less any proportion between the micro rest and the efforts have bee prescribed in various protocols, but 7:3 seems like the most common, followed by 8:2, 5:5 and 10:3.

Years ago, when I first tried repeaters they did neither increased my climbing ability nor my maximum strength, and for a few other people I have data on they actually decreased maximum finger strength by a bit. On the other hand some people report that they significantly increased their strength both on the fingerboard and on actual bouldering. Then again, from data I once collected, and from a number of small studies in the "scientific" literature (well n=9 or similarly ridiculous small samplesizes) it seems like the performance on one set of 6-7 7:3 or 8:2 repeaters is very weakly correlated with max climbing ability (boulder or route redpoints) – which is striking as the relative max load held on any single hang for basically any period of time from 2 to 30 seconds is strongly related to climbing performance.

So on one hand, several individuals report that repeaters increase strength and performance, several individuals report that repeaters decrease strength and sometime performance. And to make matters even muddier, it is been well known since MacLeod's study, a result that has also been reproduced many times, that climbers perform much better than non-climbers on repeaters at constant loads relative to max (and that sport climbers are most often better than boulder specialists on repeaters).

So what is going on?

For one we know that both long and short duration isometric exercise up muscle cell size, pennation angle and tendon stiffness. But  long duration isometric exercises have a tendency to increase muscle size more, while short duration isometric exercises have a tendency to increase tendon stiffness more. So even if I am not aware of any studies that have compared [muscle growth for ] 6x7s:3s isometric exercise with 6x7s:3min isometrics, one could maybe hypothesise that repeaters could be a slightly better protocol for hypertrophy.

However, if I may speculate further, I think the answer lies somewhere else.

For me and people with similar strength profiles 7s:3s repeaters at a load of 55% of MVC (about 60% of my 5s max-hang) is largely an aerobic exercise.  I can do 7s:3s for more than five and a half minute at that load, and from an aborted experiment on my better half, I would suspect that she could do 7s:3s hangs @50% of MVC until she gets too hungry or too sleepy.

This tells me that repeaters at 50% of MVC are mostly an aerobic exercise for me, and for my better half an almost entirely aerobic exercise. This is not too surprising as for 5*3=15s out of 57 seconds the energy contribution is 100% aerobic (mostly used to resynthesise phosphocreatine). For someone with a high proportion slow twitch fibres or strong aerobic metabolism most of the energy during the actual hangs will be either from stored creatine or aerobically created.

(Looking in a table in a random sport physiology textbook for time to exhaustion agains anaerobic/aerobic contribution shows that if doing a bout of 6 7s:3s hangs – that is 57s to failure should be about half/half aerobic/anaerobic even assuming really bad recovery during the micro rests)

The training adaptions to improve on repeaters should thus be largely aerobic in nature.

This is quite a bit different from climbing for say 45 sec to failure (3-7 moves depending on complexity) which is largely an anaerobic exercise (70% of energy produced anaerobic I'd guess). The difference is that during a bout of hard climbing the hand rest 0.3-0.6 seconds between the holds (I have this from two independent, but unpublished studies. One by Eva Lopez and the other from Carlos Cabrera). This shorter rest times makes it much harder to resynthesise phosphocreatine

So it seems likely to me that climbers are better than nonclimbers on repeaters because climbers have superior aerobic adaptions, and that expert sport climbers often (but not necessarily) have done much more climbing of aerobic type than boulderers.

 It seems likewise probable that climbers with relatively underdeveloped aerobic strength compared to their max strength would be likely to benefit from repeaters, as if they could increase their aerobic strength by a fair bit it would make a great difference on even the very hardest boulder problems. On the other hand, climbers with well developed aerobic strength, and in particular those with a large proportion of type I fibres are unlikely to improve much from repeaters as they are highly unlikely to stress the type II fibres much and totally unlikely to stress the type IIx fibres.

[jwi]

For me and people with similar strength profiles 7s:3s repeaters at a load of 55% of MVC (about 60% of my 5s max-hang) is largely an aerobic exercise.  I can do 7s:3s for more than five and a half minute at that load, and from an aborted experiment on my better half, I would suspect that she could do 7s:3s hangs @50% of MVC until she gets too hungry or too sleepy.

This tells me that repeaters at 50% of MVC are mostly an aerobic exercise for me, and for my better half an almost entirely aerobic exercise. This is not too surprising as for 5*3=15s out of 57 seconds the energy contribution is 100% aerobic (mostly used to resynthesise phosphocreatine). For someone with a high proportion slow twitch fibres or strong aerobic metabolism most of the energy during the actual hangs will be either from stored creatine or aerobically created.

Isn't the % MVC the important variable here? Repeaters used in, say, the Andersons brothers protocol, would be at a load of 70-80% or more, I think.

70-80% of what? MVC or max hang for 5s or max hang for 7s? or? I guess 7s because that would induce failure in about a minute. Regardless, if you could do them for a minute it is mostly aerobic for the reasons I have given.

MVC is maximum force held, so significantly higher than a 5s max hang.

[teestub]

Was going to comment similar to Habrich, they're definitely a PE exercise for me, I get horribly powered out after 4-5 sets (similar feeling to on the minute bouldering or foot on campussing, from the little of both I've done) but I guess I'm at a lot higher load relative to max.

I've not considered doing them at lower loads (but I do exclusively boulder) but I have found just a few sessions (around 6) makes a notable improvement in my PE on longer problems, so they make a good 'top up' exercise before trips.

[jwi]

Yes, you are aerobically underdeveloped. That's OK.

[Duma]

How would you test MVC jwi? For me I relate everything to Max 7s load - and I do repeaters for PE at 80%

The crimpd app has a session at 40% Max 7s load, and refers to it as aerobic capacity, but I very much doubt that is what most UK climbers think of as "repeaters"

[jwi]

How would you test MVC jwi? For me I relate everything to Max 7s load - and I do repeaters for PE at 80%

I rather don't want to. Too risky. I've done it a few times and now just  refer as about 1.05 times the 5s max hang.

The crimpd app has a session at 40% Max 7s load, and refers to it as aerobic capacity, but I very much doubt that is what most UK climbers think of as "repeaters"

For me at 40% max 7s load, repeaters is basically a recovery exercise. I'm pretty sure I can hang on for a few hours at those loads.

I suspect that my point is not very clear, so I try to reformulate myself:

For people far out on the endurance spectrum doing repeaters at a load that leads to failure in about a minute is unlikely to help with strength endurance as they will use their superior aerobic conditioning to deal with the load. And it will certainly not do them any stronger. It seems just like a very very unspecific aerobic power exercise (and unspecific aerobic power is well known to be inefficient).

For strong but unfit climbers repeaters with a load that leads to failure in about a minute can be beneficial for several reasons. It is likely a decent strength endurance exercise (so it actually improves strength) and will likely also help a bit with aerobic conditioning.

[jwi]

This is a cool study to understand what could be going on:
https://www.physiology.org/doi/full/10.1152/japplphysiol.00128.2002

Basically on the Wingate test (a standard test of anaerobic power and capacity for cyclic sports) endurance athletes doesn't use their full anaerobic capacity, because they don't need to: it is not a limiting factor.

[abarro81]

If you fail after 1 minute, it's got a big anaerobic contribution... otherwise you'd not be failing. Any talk of what happens at 40% or 50% or whatever strikes me a a red herring, and a bit like saying "if I climb 10m long 6c routes I don't get pumped, therefore climbing 10m routes is basically aerobic"

p.s 3 moves for 45s? How slow are you climbing?! Climb faster^TM

[Bradders]

Very much echo the view of repeaters as being a PE exercise. I've not been focusing on them recently just topping up here and there, but when I have done them I've been doing so at much more than 50% of max and the feeling/result is unquestionably powering out at the end of each set, I.e. 6 hangs 7/3 work/rest. There's no way I'm operating aerobically when doing them at this intensity.

As an obsessive boulderer who never sport climbs, I definitely see a benefit from doing them from a power endurance perspective.

The other thing I believe they are good for is general finger health. Last year I had quite a few finger injuries and doing repeaters consistently was one of the key aspects of recovery.

[Ged]

I don't thik it's useful to just say "repeaters", as it's a hugely variable exercise depending on load added.

 I have done them as a very much aerobic excercise by doing sets of 7 reps, rest 3 mins, and getting a definite pump feeling after about 7 or 8 sets. 

I usually now try and do one set a week of quite high intensity ones (smaller holds and weight added), roughly as per the Anderson protocol, but not bothering with the 7 rep set, just the 6 and 5, then rest 5 mins between grip types.  It is definitely not aerobic in any way!  I get the powered out feeling too.  No pump, just total failure.  I find the progression on these quite satisfying over a period of months.  I seem to keep on making gains for a long time, usually 2 months before I swithch to soemthing else.

I'm trying hard to not get too bogged down by terminology these days (ancap, strdength endurance, who knows), but anecdotally, it seems to give me 3 or 4 more moves at my limit when I'm training it regularly, which is quite handy for current goals (longish boulder problems and redpointing at Ansteys).

[Sasquatch]

I think the intensity question is key here. 

However, if I may speculate further, I think the answer lies somewhere else.

For me and people with similar strength profiles 7s:3s repeaters at a load of 55% of MVC (about 60% of my 5s max-hang) is largely an aerobic exercise.  I can do 7s:3s for more than five and a half minute at that load, and from an aborted experiment on my better half, I would suspect that she could do 7s:3s hangs @50% of MVC until she gets too hungry or too sleepy.

This tells me that repeaters at 50% of MVC are mostly an aerobic exercise for me, and for my better half an almost entirely aerobic exercise. This is not too surprising as for 5*3=15s out of 57 seconds the energy contribution is 100% aerobic (mostly used to resynthesise phosphocreatine). For someone with a high proportion slow twitch fibres or strong aerobic metabolism most of the energy during the actual hangs will be either from stored creatine or aerobically created.

(Looking in a table in a random sport physiology textbook for time to exhaustion agains anaerobic/aerobic contribution shows that if doing a bout of 6 7s:3s hangs – that is 57s to failure should be about half/half aerobic/anaerobic even assuming really bad recovery during the micro rests)

The training adaptions to improve on repeaters should thus be largely aerobic in nature.

Yes, if you are training at 50-60%, then you're training in the aerobic zone and you'll see aerobic adaptations.  If you are training in the 80-90% range, the gains will be largely anaerobic instead.