Muscle metabolism in a nutshell (recap of part 1)
This is part two of the ‘muscle metabolism’ article series. In part one (link) we have analysed human muscle metabolism, how muscles are supplied with oxygen, and how they store fuel. We learned that muscles store fuel in the form of ATP (adenosine triphosphate) and CP (creatine phosphate). These fuels are metabolized without using O2 or producing CO2. Muscles are supplied oxygen from the lungs through the bloodstream and through myoglobin. Slow twitch muscle fibers (those that you engage while walking around) contain more myoglobin. However, human muscle contains limited amounts of myoglobin compared to freediving mammals. Fast twitch muscle fibers (those you use during strenuous exercise) contain more high energy phosphates (ATP and CP).
We also analysed the metabolic pathways in muscle. Aerobic glycolysis is slow but is the most efficient metabolic pathway. It generates 34 ATP molecules out of one glucose molecule. Anaerobic glycolysis produces lactate and generates only 2 ATP molecules out of one glucose molecule. Because the reaction occurs faster more energy can be liberated quickly. This process can be dominant for a maximum of 75 – 120 seconds. Anaerobic alactic metabolism uses only high energy phosphates (ATP and CP) present in muscle and can be dominant for about 5 – 15 seconds.
Did you miss part 1 of the muscle metabolism series? Find it here.
Muscle metabolism: concurrent metabolic pathways
A persistent myth in exercise physiology is that all these metabolic pathways are active sequentially. On the contrary, they are actually concurrent. In the figure below you can see the relative contribution of the different metabolic pathways to power output during maximum intensity exercise.
You can see the overlap in time between the different metabolic pathways, but also that the anaerobic systems contribute more at the onset of exercise than at the end. Of course a dive is not a continuous maximum power output. This might be what happens during sub-maximal power output:
Regardless of the intensity of the exercise, the ATP-CP system is the quickest to respond to a muscles’ energy demand. The ATP-CP system essentially fuels the muscles while the blood flow to the muscle increases as a response to the increased oxygen demand. The increased blood flow allows aerobic metabolic pathways to provide energy. If the energy demand is low the lactic anaerobic system will not be a major contributor.
What happens if we run out of oxygen?
But what happens if oxygen is removed from the equation? How does the body respond?
During a dive you try to conserve as much energy and oxygen as possible. Freedivers work hard only for the first 10 or 20 seconds in order to overcome positive buoyancy, and perhaps a bit longer on very deep dives.
In the figure below is a hypothetical ideal dive and the energy systems that are major contributors to it. The dive consists of three phases, the dive phase, the sink phase and the ascension. During the dive phase you are actively swimming down. Ideally the ATP-CP system is the only contributor to the entire swim to neutral buoyancy. During the sink phase you stop moving and the aerobic system is able to supply enough oxygen to your body for basal metabolic functions. During the ascent most of your energy will be derived from anaerobic and aerobic glycolysis.
A less ideal dive
In a less than ideal situation the lactic anaerobic system may also supply some of the energy required for the descent. In this case you deplete the ATP-CP system completely prior to reaching neutral buoyancy and anaerobic and perhaps also aerobic glycolysis supply significant amounts of energy. The obvious result is that there will be less energy available for the remainder of the dive. A larger reliance on the anaerobic glycolytic system will also lead to earlier muscle fatigue. This may occur if you have a very thick suit, not enough weight, or you are not appropriately trained.
If the oxygen supply to the muscles becomes limited, either because of vasoconstriction, hypoxia or both, anaerobic glycolysis supplies the majority of the energy required. The dive reflex has a large impact on the oxygen supply to the muscles. Vasoconstriction limits the supply of oxygen and causes anaerobic glycolysis to start earlier. Anaerobic glycolysis leads to muscle fatigue, which you notice as burning legs on the way back to the surface.
Muscle metabolism in diving animals
The processes that operate in human muscles are similar in freediving animals. However, the muscle composition of species differ. Diving animals also have specific adaptations that help them dive longer and deeper.
Diving animals do long breath hold dives because adaptations. These adaptations include a high hemoglobin concentration, a high blood volume relative to body weight, and abundant myoglobin in the muscles. In addition they have metabolic adaptations that help them dive. Despite these adaptations, the basic metabolic pathways are the same as in humans.
Some animals, such as the Weddel seal, dive on an exhale so that they do not struggle to reach neutral buoyancy. The Weddel seal maintains low levels of aerobic metabolism throughout most dives. These seal have less of a dependency on blood borne oxygen because of the massive amounts of myoglobin in their muscles.
Other diving animals push to the anaerobic limit on nearly every dive, such as sea lions and penguins. The muscles of Weddel seals are predominantly composed of slow twitch muscle fiber and loaded with myoglobin. The muscles of sea lions and penguins contain more fast twitch muscle fibers. The difference in muscle composition exists mainly because of foraging and hunting styles.
What should you do? Hit up the gym and train for fast twitch muscles? Or try to be like a Weddel seal?
In essence the diver that emulates a Weddel seal will end up doing the longest and deepest dives. The dive profile of spearfishers is much like that of seals. They make a descent, stay at their target depth for a third of the dive, and then ascend. It is no coincidence that many spearfishers have hit amazing numbers at freediving competitions. And this despite the fact that they never did much training specifically for competitive freediving beforehand
So you tell me in the comments, are you going to hit up the gym, or start spearfishing?
Three studies that you may find interesting:
- Kooyman, G. L., & Ponganis, P. J. (1998). The physiological basis of diving to depth: birds and mammals. Annual Review of Physiology, 60(1), 19–32. http://doi.org/10.1146/annurev.physiol.60.1.19
- Gastin, P. B. (2001). Energy system interaction and relative contribution during maximal exercise. Sports Medicine (Auckland, N.Z.), 31(10), 725–741. http://doi.org/10.2165/00007256-200131100-00003
- Reed, J. Z., Butler, P. J., & Fedak, M. A. (1994). The Metabolic Characteristics of the Locomotory Muscles of Grey Seals (Halichoerus-Grypus), Harbor Seals (Phoca-Vitulina) and Antarctic Fur Seals (Arctocephalus-Gazella). Journal of Experimental Biology, 194, 33–46.
Muscle metabolism part 1: Muscle fiber types and freediving.
Facinating…
Helps to explain some things.
I have a long breathhold. Before I started free diving and learning how to breath up..I could repeatedly do a 5min. dry static.
I’ve done submerged wet statics in excess of 6 min.
I’ve never been able to push my limits at depth…but my best spearing dives were on casual inhalation…up to 2:15 min.at 60 ft.
I typically come up sooner as it makes my dive buddies nervous…understandably.
I know I have a high co2 tolorence…contractions are mild if any.
I’ve tried long breathups and max inhalation and more often than not my urgency to breath occurs by the time I reach bottom or my target depth.
This I can’t explain.
I experimented with dynamic exhale hold in the pool and found it felt relaxing and natural until the very last moment… Contractions and the urgency to breath became extreme.
I’ve never attempted any real depth on exhale….however I’d like to.
Hey Oliver, thanks for sharing your experience. That is interesting indeed. Make sure you are very careful with depth diving on an exhale, you do risk a lung squeeze by doing exhale depth dives. Some divers say that their breath holds are much more relaxed on exhales, and it might be because of two reasons, 1) the dive reflex may be stronger on an exhale (differs per individual) and 2) you are not creating as much CO2 on the way down.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0201401
Sounds like my abilities 🙂
The Weddel seal method for me thanks 🙂
Would have guessed as much from the seal whisperer.
Hit the gym or take up spearfishing? Well, I already spearfish and don’t much like the gym, so I think I’ll keep diving FRC, half lung in my case.
Snarky comments aside, Thanks! for the article. Great food for thought. It explains a lot about the muscle physiology which contributes to FRC diving. I think it explains why I don’t get leg burn even on very long (2 minute plus) dives to 80-90 ft. Even with a strong dive reflex (blood shift) there is some blood going to the motor muscles. Diving FRC is so much more energy efficient(way less force needed to to get up and down), that you don’t need much 02 to the muscles, anerobic glycolysis kicks in early and between the two (or three?)pathways, energy needs are covered. Mine will feel “dead” on the way up, but very seldom burn.
Thanks again!
Thanks for sharing your personal experience. I agree, with you, that the biggest plus of FRC diving is probably the difference in buoyancy. 1) it is easier to sink, and if you use less weight because of that 2) it is also easier to come back up! It’s a double whammy really, were it not that equalizing is harder and of course you can’t bring as much oxygen down.
2 min + to 80/90 ft is a long time on FRC!
Equalization (and squeeze) are DEFINATELY issues when diving FRC. It took me a while to learn how to avoid squeeze. FRC does cut your depth limit, but unless you like to line dive deep, a little practice gives all the depth that most divers can use. In my case, I don’t want to dive deeper than my equalization limit( around 100 on good day), not enough bottom time and I lose coordination coming up from around that depth with a Dolfin. Funny, but bifins work fine.
Suggestion for a future article: Compare the physiology of the 3 styles of lung inflation, full inhale, full inhale plus packing, and FRC. You have the data and knowledge to do that. It would make for some interesting discussion. Could be a series of articles, physiology, where each works best and why, effect of circumstances, depth, wetsuit thickness, water temp, etc. I’ll bet Eric would like to contribute to that.
I’ll keep that in mind, it’s a good idea. How did you manage to avoid squeezes during your dives?
I’m lucky enough to feel squeeze discomfort before major damage is done,coughed hard and felt damaged, but never bled, etc. Getting squeezed would reduce my depth ability in a major way, until it healed, a month or more. Having had more than a few run-ins with squeeze, I’ve learned what it feels like when I’m getting close and just don’t go deeper. That’s trickier than is sounds, cause squeeze will really sneak up on you. Several times, I got squeezed by a pressure contraction on the way back up.
I also do several mornings a week of stretching, diaphragm and intercostal. The diaphragm stretchs are done full forced exhale, plus reverse packing as far as I can go. When I started that, I could tell that if I kept on reverse packing, I’d squeeze myself. As time went on, my lungs adjusted and now I can reverse pack till no more air will come out, with no feeling of near squeeze. My lung tissue has adapted to high levels of negative pressure, which makes my lungs very resistant to squeeze.
The combination of bad and too many experiances with squeeze and the extreme exhale/stretching keeps my depth ability at least reasonable, 80-90 ft, before I feel squeeze getting close. Go diving everyday for a couple of weeks and I can go deeper. Stop doing the stretching for a month or so and my depth ability declines to 60 ft. Been there, done that, won’t do it again.
Thanks for sharing! You’ll have to show me your stretching routine in a couple months. It is really interesting that your body responds so quickly to both every day diving and stopping with the stretching.
Thought of something else that might help some divers.
For me, squeeze involves a muscle tensing process that, once started, is hard to stop. I can’t just stop descending or come up just a little.
Once it starts, muscles in my chest and diaphragm tighten up, increasing the negative pressure in the lungs and setting me up for a pressure contraction, which are much stronger than normal contractions, cause a large further increase in negative pressure and are dead certain to cause squeeze damage.
Once the process starts, I have a few seconds before things get dangerous, which allows enough time to come up a lot, like 20 or 30 ft, which is enough to stop the process as long as I do it fast.
Good added thought. I experience the same thing, but it starts as a tight feeling in the solar plexus. During a static this tightening can be anywhere from 10 seconds to 60 seconds before the first contraction. I’m not sure how long it takes in the water, but my contractions have never led to squeezes. Presumably because I dive on a full inhale and am not deep enough to get a squeezed from a contraction.
There is a substantial difference between c02 contractions, which is what you seem to be experiancing, and pressure contractions, which are much much stronger and brought on by compression of the chest. I don’t think all divers get them, at least few talk about it. I had some crazy strong ones when I first tried diving deep (at about 80 ft), diving full lung at the time. My body has learned not to do them unless I go way down into negative pressure and I have learned what they feel like coming on and get the heck out of there.
You’re right, I was talking about CO2 contractions. I thought the pulmonary stretch receptors only indicated that the lungs were overstretched. Perhaps nerves in the diaphragm signal that it is flexed beyond residual volume and cause a pressure contraction. I will have to research those a bit.
Not sure what causes them, but you might be able to bring one on by doing a full exhale, then reverse packing until it gets uncomfortable. If your diaphragm tries to do a exceptionally strong contraction, thats it. Do it carefully, you can squeeze yourself, right there in your living room.
I’ve been doing lot’s of exhale dives in the pool; 10x exh+static+ 25m swim, and I find my bottom times are increasing, DR increasing, relaxation increasing. But I like to carry the empty lung positives to the full lung dives. Suggestions welcome.
Hey Kars, I think that exhale statics plus swims are a great way to train because it creates hypoxic conditions faster than a full inhale static and swim. You are essentially training the muscles to perform under hypoxic conditions, and because of that hypoxia the dive reflex should become stronger. Whether you are able to carry this over to full lung dives is not easy to say because a major trigger of the DR is hypoxia. Apart from that you will accumulate more CO2 on a full lung dive, which may cause an urge to breathe. I have used a similar method and found I still needed some form of CO2 tolerance training.
Just back from this evening’s training. We did a couple of full lungs long dive time slow dynamic dives, followed by a dive that last the same time, but now with a higher swimming speed. In the past I did not have much vascular constriction, but now there is. I think I need more of these dives to get more comfortable with the contractions and discomfort. I’m at 2′ dive time now, but love to creep up to 3′ dynamics in the future.
Hi Kars, glad to see you adding your knowledge to this site.
Lacking a buddy, I’ve been doing a lot of dry experimentation, aimed at improving chest flexibility and discovered that it also improves blood shift. I’ve also found that given lots of dry exhale (short) statics, I can still get a decent blood shift with a larger inhale and that larger inhale(roughly half lung) provides a much longer comfortable static. Not sure exactly what is going on, but I think you are going to find that at least some of the benefits of exhales (and diving FRC) begin to show up in your full lung dives. It takes a while.
So Kars & Connor, here is a question for you: how do you gauge vasoconstriction and bloodshift during your statics / dynamics?
Do you feel a tingling in your arms and legs (I feel this before the onset of contractions during my statics) or do you get very tired legs at the end of a dive (potentially the effect of blood shift resulting in muscle hypoxia)?
Doing dry exhale statics, I get a strong sense of wanting to move, twitch, my fingers and arms as blood shift sets in. “Tingle” isn’t quite the right description. Sometimes I can feel shift in my legs, not always. When I start breathing again, I can feel blood returning to legs arms and back.
On real dives, the feeling of wanting to move my fingers is strong when blood shift should be strong. On long deeper dives with bifins, where it takes a while and some work to ascend, my legs will feel very empty and tired, occasionally burn, but not often. With the Dol-fin, I seem to lose power and coordination on long ascents. Not sure what that is all about. A few times, I’ve had to come up the last 20 ft or so with my arms.
I’m diving half lung with little or no suit, so getting down requires very little effort. Coming up is far far less effort than in a cold water/heavy suit situation. I suspect that the blood shift reduced amt of blood flow still going to the muscles is enough to prevent burning on ascent, since I’m not really working all that hard.
He he Connor! Are you here too?!
Yep the empty training is already helping me.
I’ve been long without a buddy too, but am now happy to report we have a nice cosy 7-8 person group. I’ve just taken a look on my heart rate recording dive computer (Omer -UP1) and studying it’s graphs.
On full lungs, very slow using small fins, 50m dyn, HR starts at 100, drops to 60 at 20″, then gradually drops to 45 @ 1’06” and stays at 45 until 1’53” resurface.
On full lungs, medium speed dyn small fins (83m), start: 98BPM, 10′ 68BPM, 25′-76BPM (!), 1’06”-68BPM, 1’10” -49BPM (!), 1’50”-44BPM.
As you can see my HR does fall fast at the start, but it does not fall very low because I’m swimming medium speed (medium effort). When my SAO2 crosses below a certain threshold,vascular constriction and my HR drops fast from 68 to 49 BPM, from which is gradually goes lower. The difference in low and medium effort is easy to see, with the easy dives my HR initially drops 10BPM deeper, and then continues to drop to the 47bpm and levels out to 45bpm. With the medium effort it has less initial drop, RISES 8 BPM, then gradually lowers, then drops to 47BPM to finally tapers off to 44 BPM.
I did also some monofinning too; a high effort activity, concentration and muscle use. The first rushed dive was from start to finish 133BPM, needless to say it felt rubbish and was short of 50m. The return dive was a bit better, also full lungs. Start 91bpm, curving up to 107 at 20″ then a flat line of 104bpm to the end. As you see the full lungs, high intensity effort, did not allow for much HR drop. BTW I did not have much O2 reserve when I surfaced.
The things I’ve (re)learned from these graphs are:
– Start my dive with a 20″ very low effort start or static to allow my HR to drop fast, then swim with such low effort that my HR stays low.
Something else also have noticed.
When I was doing empty lung dnf dives+sta, I was negative at the 5m bottom. According to the depth graph the HR appears to rise when I bring my arms over my head forward.
I have some plans for testing the next sessions, but I love to hear your experimentation suggestions.
Thanks
ps Connor, I hate dry statics… For training I believe full exhale is more beneficial; but maybe you know why/how FRC could be helpful or better is certain situations?
As per Connors suggestion I am working on a post on energy expenditure during dives. Specifically I am calculating how our buoyancy affects energy expenditure. There are a lot of variables to consider but so far it appears that in some cases (thin or no suit, specific body type) exhale dives are more energy efficient. Seals (phocid seals, like the grey seal and weddell seal) dive on an exhale too. Previously researchers thought this was a strategy to counter decompression sickness, but now many researchers think it is a strategy to conserve energy.
I cannot tell when bloodshift sets in myself for sure. I do not practice dry statics very often, and in the ocean I wear an 8mm suit + 13 lbs weight. Whether my legs are wasted at the end of a dive usually has to do with the length of my breathe up. A breathe up shorter than 2 min, and my legs will be tired after a dive to 25 m or deeper. Longer than 3 min and it is usually not a problem, unless I do a dive that is longer than usual.
@Kars, that is very interesting data. It would be really interesting to see the graphs of for example a session of 10 exhale dynamics and a session of 10 full lung dynamics. Perhaps even slow vs. fast and so forth.
Kars, what you see on a low effort dynamic is what happens with half lung diving. Just for grins, try medium to high effort after 1:15. Your DR should have set in strong by then and should keep your HR low till you start breathing again. Thats what happens to me. Typical dive, 80 ft, 1:50, surface dive and two light kicks, drift down with no further effort. HR will be somewhere in the mid to low 50s at the bottom and doesn’t change much all the way to the surface, even with lots of effort and a strong urge to breathe near the end.
Dry empty statics: I agree, HORRIBLE if you continue very long. I’m not going long, more interested in stretching the chest and diaphragm and setting off my DR. MarcinB has an interesting approach. He is training hypoxia with empties, hyperventilates to knock off the co2 than goes for astonishingly long empty statics.
Training FRC vs empty: I think you are right for dry and pool training, not sure about open water. Empty is so much faster, but I suspect that open water training, with its far more complex environment, will be better done at the lung inflation you normally dive with. Exception is training depth equalization. There, empty would work better.
Jaap, Half lung/FRC dives are definitely more energy efficient for me(skinny, none to modest(3 mil) suit, modest depth).
Interesting that you don’t feel blood shift. Does your heat rate fall during long statics or longish dives? If you are experiancing a good blood shift, I’d expect to see your heart rate fall into something like the low 50s.
For humans, DCS and narcosis issues are supposed to be much less with FRC diving. I think I have experianced FRC effect on narcosis. Since narcosis is rapidly becoming the limiting factor on world record CW dives, I wonder if is room for adapting FRC approach to depth.
Thanks for the replies Jaap and Connor, inspiring information.
I have some data on the 10x empty dives. I’ve done that in the following way: Exhale, duckdive to 3,2m, static, 25m swim, surface. I’ve not recorded my HR or times on those dives, but I like to record it when the opportunity occurs, which may take a while because my work season has started and I have little time. Anyway the observation was that after 8 or 10 of those empty dives, the 50m full lung medium speed CO2 DNF schedule dives felt incredibly easy.
Another data point would be my last long DNF, about 2,5 years back. Full lungs ~105m. In this dive I started with a very slow speed, waiting for the the HR to drop, focussing on having a low circulation and relaxing. At about 40m when I felt the HR drop, I started to swim gradually a bit faster, at 75 still a bit faster reaching a little bit over medium speed at the end. The theory I tested was to focus only on blood circulation, to have it a low as possible, and keep it low. And this dive confirmed to me that this is the key for me.
In relation to deep dives, I have more vascular constriction because of the water pressure, hence I’m better at CWT then DYN.
I wonder how the athletes would do if they would specialise to dive
1) forced empty, 2) passive empty, 3) Full, 4) Packed.
But at the same time Eric Fattah, also a pioneer for FRC, did do his latest Canadian CWT record packed full lungs. Proof is in the pudding, but I’ve not seen FRC dives even take a NR, let alone a WR.
I’m starting to think one of the big benefits practising empty lungs is very beneficial because it takes less time, more transition moments, more time spend anaerobic.
Connor, I yet have to try hyperventilation + empty static, thanks!
Jaap, have you seen how Guilliaume Nery starts his CWT dives? What I see is him slowly rolling over, have a little pause and then smoothly duckdive and slowly starts his dive. I think this makes a lot of sense if you think about relaxation and bringing / keeping the blood circulation down. Maybe we should try in out next line dive session different CWT starts. 1) Regular fast duckdive and fast swim to negative buoyancy. 2) Roll over relax for 20 seconds (static), then duckdive and slow and smooth swim down to negative buoyancy – focussing on getting and keeping low blood circulation. 3) Roll over, slow passive exhale (20 s), duckdive.
Thanks for the discussion; it almost feels like the good old Deeperblue times 🙂
I agree, I love the discussion. This article has improved so much simply because of the comments!
A few ideas:
1) So you are in part gauging the bloodshift by the drop in heart rate? If I may say so, my peers in science would probably say: ‘you are measuring heart rate, not blood shift. They may commence at different times during the dive’. Of course I cannot vouch for the sensations you feel in your arms and legs, as I don’t believe I feel them.
2) My resting heart rate is around 44. I don’t feel a large drop in heart rate unless I start with an elevated heart rate. Perhaps this is the reason I do not feel the DR starting, or bloodshift. Although my heart rate may drop to 38 or lower, I don’t feel it during the dive (I would LOVE to measure this, but don’t have the means currently).
3) Unfortunately, I cannot test a ‘slow’ descent because our water is always stinking cold… But Kars, my calculations include exactly the parameters you talk about (forced exhale, FRC, full lungs, packed volume). I am currently waiting on neoprene specs and then I’ll post the article.
4) Regarding Guillaume N.’s dives, My best dives have been when I have done descents that are easy. Minimizing energy expenditure is key. However, the minimization should be done during the entire dive, rather than only during the descent. for me personally that means that I cannot just don weight until I descend easily, because I would hardly be able to come back up.
5) I agree with you, I hate dry statics. They are so uncomfortable. I have done hyperventilating exhales to 3:45. Hyperventilation statics are the easiest way to get super hypoxic in my experience, but I don’t think they do much for the in-water dive reflex.
Ditto on the quality of the discussion.
Correct, we are measuring heart rate rather than blood shift, but HR is almost certainly a good proxy. The logic: As blood shift limits circulation to the skeletal muscles, blood pressure will go way up unless the heart slows down (and maybe stroke volume declines?) The body is pretty good at regulating BP, hard to envision the heart not slowing down under blood shift conditions.
There seems to be a lot of variation among divers in HR changes during a dive. Could be genetic propensity to blood shift, sensitivity to BP rise, or differing heart response(HR vis stroke volume), or other factors involved in DR or ?
Jaap, the polar heart rate monitors are good to at least 100 ft. They work through a 3 mil suit, not sure about thicker.
I will get myself one of those monitors.
I noticed that my heart rate goes up on a full inhale (at least momentarily). The heart is confined to to a smaller space as the lungs fill up. As a result the stroke volume goes down and HR goes up. Part of the drop in heart rate during a dive may be the result of the lung compression. This compression allows the stroke volume to go up and the HR to go down again.
Mind you I don’t doubt that blood shift occurs and that it is accompanied by a HR drop, I’m just wondering about how exactly they relate. Could you say that a 20% HR drop implies a full bloodshift (maximum vasoconstriction) or does a 20% drop correspond to 50% vasoconstriction? It probably differs per diver.
Kars, check your DB conversations
Heart rate is a good proxy for the existance of blood shift, and a very large drop propably signals a stong shift, but its hardly an exact proxy. Too much variation among divers. Kar’s drops like a stone, mine drops, but slowly and not so much. Based on how my arms and legs feel, I’m suspicious that my blood shift is a good deal stonger than the HR drop indicates.
Super interesting. I think that because my heart rate is already low it is hard for me to identify a when it lowers further without a heart rate monitor. I have some minor strange feeling in my arms and legs when I hold my breath but I don’t believe it is as strong as for you and Kars. I will pay more attention to it. I can do statics over 5 min so there must be a dive reflex, I just can’t feel a clear onset of it.
One good way to see blood shift using a heart monitor is to swim hard at the end of a longish relaxed dive. If your HR doesn’t rise, or very little, its a pretty good indication that blood shift has set in hard and is not releasing due to exercise. On a good dive, mine stays low until I start breathing again, then shoots up.
Hello chaps, a little update from me.
On yesterdays training, we repeated last week’s exercise, 2 slow long time dives (2′) followed by a 2′ with more speed. As you recall the faster 3 dive last week differed in the Heart-Rate graph, with an initial drop 98-68(0-10s)then a HR rise 68-76(10-25s) then a drop 76-68(25-65s), a steep drop(DR-Anaerobic) 68-49(65-67s) followed by a gentle slope down: 49-43 (67-110s).
Comparing this to the previous 2′ dives, you see that the initial faster swimming leads to a much higher HR in the beginning of the dive, until the anaerobic phase starts. I also saw and indication that holding my arms over my head may have influence.
Yesterday I choose to use a monofin, not the small bi-fins. I did the first two slow 2′ dives with arms over my head, and the HR graphs looked like the 3rd -faster (!) dive of last week. With monofinning I hold/have much more tension in my body because I want to have a reasonable streamlining. But as I noticed this partially prevents my HR from dropping.
On the 3rd dive I decided to swim monofin with my arms to the side until the DR is manifested. Now the Initial HR drop (around 25s) is 10 BPM lower (66), and after a tiny rise (68) it linearly drops down to 45 (90s), from which it stays at 46 until I resurface at 134s.
I switched over to arms over head at ~70s, and from then on swam at a normal pace.
From this experience I see 3 possible areas of improvement:
– start, having the initial HR drop earlier.
– swimming speed with arms to the side.
– swimming speed with arms above the head.
Looking a the HR graph, I’m pleased to see that with this tactic the initial HR drop is deeper, and there is a no longer a hi rise and higher HR until the second HR, DR drop. The graph looks smooth too.
Ideally my HR graph would look like my static curve, and looks like a bucket with a little bump of sand on the left side 😉
My Omer HR monitor actually proves to be useful in training, making the effects of subtle changes visible.
Question Jaap, are you Dutch? If you’re close you are invited to test my HR monitor in the Eindhoven -Tongelreep pool next Tuesday 18:00-20:00.
Very interesting data Kars. I wonder how your HR drop manifests itself if you start with a 5 or 10 second static before your dive. Sounds like your computer is a gem for tweaking your dives.
I am Dutch, but not very close, I live in Vancouver, Canada. I will be in the Netherlands at the end of summer, so I will send you an e-mail closer to that time if that works. Maybe we can do a local dive too.
I went out for a dive yesterday and wanted to try FRC. I did short hangs < 1 min at 5 – 10 m. I will have to get used to the sensation in the chest. What I noticed afterwards on two dives to 30 and 35 m, was that my legs were so tired (severely vasoconstricted?) that I could not swim full speed up. I wonder if the FRC hangs kickstarted my dive reflex. I felt like I had minutes of air left coming back up, but was tempted to grab the rope because my legs were so tired. My 35 m dive took nearly 15 seconds longer than usual.
Thanks Jaap,
I’ll try a 25 second static, followed by a hands down swim.
Please do write me, love to meet fellow freedivers!
In regard to your FRC experience, my experience is similar.
I think your prep dives gave you a nice stretch, and helped you to relax into this empty state, getting used to it. The static allowed your HR to go low as well, conditioning your response. For the 30 and 35m dives you may have started them slower and more relaxed than usual. And keep that relaxation on the way down because you’re not getting near your chest stretch limit. This all helped you to have a lower circulation on the way down, and your limbs went anaerobic earlier, hence you came up with tired legs and plenty of air in the blood. Maybe you should try the same as you suggested to my dynamics, do a 25 second static and then dive?
As a side note, one exercise I found to be very beneficial to find relaxation at depth is: duckdive to -10, sit on the bottom, relax the body and exhale tiny bubbles until empty, then swim up. See when you’re holding air it often involves many more muscles then the mouth. When you exhale you’ll realise how many muscles on your chest, neck etc you were tensioning, it’s remarkable. My buddy had problems passing 10m, we did a few of the above, then he instantly went to 20 WITH EASE!
Always good stuff, Kars. Very interesting. Why would having your hands/arms above your head increase heart rate?
Jaap, how close to empty is your FRC? Mine is almost empty when in the water on the surface. A heavy suit would make it even worse.
One thing a series of FRC or empty dives will do is cumulatively increase you blood shift. When diving with less than full lungs, the blood that shifts to the lungs is not all pushed back into the rest of the body. The cumulative aspect makes for faster, stronger blood shift on later dives, which you seem to have experianced, as well as being protective against squeeze.
I think my FRC is fairly close to empty with my suit. I will try the static prior to the dive. I was really surprised at how tired my legs felt, and I believe it is the effect of a stronger dive reflex after FRC dives. I usually have to do a slow warmup to get to the 30 – 40 m range, but this time could do over 30 m after just a few dives to less than 10 m. I am going to experiment with this more. On another note, my legs have never been so sore after diving… It was an eye-opening experience.
@Kars, I’ll try the static prior to the dive too. Should be interesting.
Jaap, the quicker progression to 30m is very likely the result of cumulative blood shift and/or something else related to strong activation of DR that the FRC/empty dives create. I find the same thing. My comfortable equalization limit increases by at least 10 m over the course of a diving day
I am going to keep experimenting with it. In the cold PNW it would be fantastic to kick-start the DR with FRC dives (or another technique) because we can only use little time for the warm up.
Jaap, I believe I breathing slow and minimal as a preparation for a deep dive helps to lower the metabolism. I used this for my 65m CWT NR in Sweden. The dive went great. Without any in water preparation btw.
Hey guys, here a quick report on the my low HR start dynamic test.
Because of team considerations I had to do this test after 1 hour of CO2 training in the other pool. This dive was made in a 1,9m deep 50m pool.
As planned I started full and packed with a monofin with a 25 second idling like slow pace. I was too buoyant so I had to wiggle my fin a bit to stay at the bottom. Around 25s I was at ~15m, and started to swim a little bit faster while keeping my arms to my side. At 1 minute I was around 40m, 50m turn at 1’08” and knowing that my DR should be manifested I put my arms over my head and started swimming normal speed. My 2′ alarm went off at around 80m, And I pushed on to reach the 99m in 2’30”. I surfaced with a samba, but managed to hook through it without others noticing it, besides my safety standing in front of me.
The graph looks very much to my liking. At 0’00″it was 131bpm (packing), then 3″ later it was at 59bpm (!). from this it went a bit up to 63bpm @ 15″ from there it went down to 60bpm – 25″ then down to 46bpm @ 1’26” from which it stayed at the same bpm.
One discrepancy is the time my HR monitor recorded (2’03”) and the time my buddy recorded (2’30”). I’m also using a count down timer set to 2′, So I get 1 beep at 1 minute, one at 50″, one at 40″, one at 30″, one at 20″, one at 10″ , and one every second the last 5 seconds, followed by triple peeps (alarm) for 30 seconds. Maybe I went too shallow (< 1m) and the computer stopped recording the dive?
Lessons I took from this dive:
– super slow start reduces the HR / circulation,
– arms to the side reduces HR.
– have a bit more weight.
– normal swimming speed after DR does not raise the HR.
This time I packed a good amount of air, maybe I want to see if a normal full breath has a good affect on HR, DR and Dive time. In my PR / top days I recall that my dynamics where around 2'30" – 2'40" covering 150 dyn, 111m dnf.
On my dive watch I can set a lower HR alarm; maybe I should set it to 55bpm (~35 seconds in the dive above) and wait for this to go off before I start swimming normal speed.
I also see value in learning to swim slow with minimal effort and arms to the side to cover the time and some distance the first 30-45 seconds of my dive. On the second half of the dive I wonder how fast I actually can go without my HR rising.
Questions and suggestion welcome.
Hey Kars, very cool you were able to do your 65 m without in water prep. I find it very hard to do deep dives without any in-water preparation, but then again, I have also never really had a good chance to try (no diving platform). I’ll keep experimenting with FRC. It does appear that I can reduce the warmup a lot with FRC dives so far.
Again interesting numbers. I wonder if a real static at the start would allow DR to start even earlier. Maybe 10 or even 5 seconds would be enough for a HR drop (in your case), so that you can start swimming with the hands over head right away (after the static). It would avoid wasting energy on drag.
I should give that 10s static a try too.
I should also learn to swim for efficiency, because at the moment For the depth I did prepare, but it was dry. Ribcage stretching, diaphragm stretching, main muscles stretching, 1 banana, herbal tea, hot shower, nasal wash, not in this order 😉 I put on my suit on 15min before Official Top, went into the water 6 min before OT.
My next pool session is over 2 weeks. Thanks!