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Thoughts on this Ab Bench?

People are really underestimating the power of the weighted chin-up.

Other than my other compound exercises, I don't normally do ab exercises.
 
I have a 10-pack.

And it is functional! It works and I can use it in dyanmic tasks.

patrick
I highly doubt your claim of a 10 pack, (you're more than welcome to prove it, of course) but whatever. I actually agree with most of what you're saying and don't presume to know more about this subject than you, however it seems as though you're taking the research to an extreme. If everyone followed your logic, we may as well just forget about doing any kind of sport, and simply walk around (or maybe just sit, no wait...not sit, that's bending...so just stand) with a spinal/abdominal brace so as to keep us perfectly align. Fact is, many activities require us to make the exact same movement you're condemning.

I think the key is not to avoid the activity altogether as that would only make those muscles weaker, but the research shows that it is the repetitive and excessive repetitions that cause the problems. I'm guessing no movement is good for you that requires hundreds of repetitions to be effective. This is why I agree that crunches and situps are no good, however I do agree with weighted ab work that still requires me to bend at the waist/hips, I just don't make it the core of my workout and I keep my reps very low. I also incorporate your suggested alternatives, and I get plenty of stimulation from the compounds I do, but nothing gets them like direct, properly executed weighted lifts IMO.

As far as being functional, how many other muscles do you recommend working with mainly static exercises. I get to do all your exercises and then some, so as far dynamic goes, by definition I believe I've got you there. I can lift kids from a burning pit with my legs while hanging from a bar as well as allow women to cross said pit on my back by creating a bridge. You might save the women, but those kids kids are toast if it's only you around to hear their screams.
 
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People are really underestimating the power of the weighted chin-up.

Other than my other compound exercises, I don't normally do ab exercises.
Which explains why you don't have any front shots without a shirt, but plenty of back. Hey...just sayin'
 
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Which explains why you don't have any front shots without a shirt, but plenty of back. Hey...just sayin'

I feel no need to "prove you wrong" so to speak, but I've posted plenty of pictures in my journals where I wasn't wearing a shirt or showing my back.

I'm leaner in my stomach and bigger in other places now than I was back in February '08, which is the last batch of pictures I have of myself.

As an ectomorph, my abs are one of my best attributes from a bodybuilding perspective.
 
I highly doubt your claim of a 10 pack, (you're more than welcome to prove it, of course) but whatever. I actually agree with most of what you're saying and don't presume to know more about this subject than you, however it seems as though you're taking the research to an extreme. If everyone followed your logic, we may as well just forget about doing any kind of sport, and simply walk around (or maybe just sit, no wait...not sit, that's bending...so just stand) with a spinal/abdominal brace so as to keep us perfectly align. Fact is, many activities require us to make the exact same movement you're condemning.

I think the key is not to avoid the activity altogether as that would only make those muscles weaker, but the research shows that it is the repetitive and excessive repetitions that cause the problems. I'm guessing no movement is good for you that requires hundreds of repetitions to be effective. This is why I agree that crunches and situps are no good, however I do agree with weighted ab work that still requires me to bend at the waist/hips, I just don't make it the core of my workout and I keep my reps very low. I also incorporate your suggested alternatives, and I get plenty of stimulation from the compounds I do, but nothing gets them like direct, properly executed weighted lifts IMO.

As far as being functional, how many other muscles do you recommend working with mainly static exercises. I get to do all your exercises and then some, so as far dynamic goes, by definition I believe I've got you there. I can lift kids from a burning pit with my legs while hanging from a bar as well as allow women to cross said pit on my back by creating a bridge. You might save the women, but those kids kids are toast if it's only you around to hear their screams.

You're really missing the point here.
 
I highly doubt your claim of a 10 pack, (you're more than welcome to prove it, of course) but whatever. I actually agree with most of what you're saying and don't presume to know more about this subject than you, however it seems as though you're taking the research to an extreme. If everyone followed your logic, we may as well just forget about doing any kind of sport, and simply walk around (or maybe just sit, no wait...not sit, that's bending...so just stand) with a spinal/abdominal brace so as to keep us perfectly align. Fact is, many activities require us to make the exact same movement you're condemning.

I think the key is not to avoid the activity altogether as that would only make those muscles weaker, but the research shows that it is the repetitive and excessive repetitions that cause the problems. I'm guessing no movement is good for you that requires hundreds of repetitions to be effective. This is why I agree that crunches and situps are no good, however I do agree with weighted ab work that still requires me to bend at the waist/hips, I just don't make it the core of my workout and I keep my reps very low. I also incorporate your suggested alternatives, and I get plenty of stimulation from the compounds I do, but nothing gets them like direct, properly executed weighted lifts IMO.

As far as being functional, how many other muscles do you recommend working with mainly static exercises. I get to do all your exercises and then some, so as far dynamic goes, by definition I believe I've got you there. I can lift kids from a burning pit with my legs while hanging from a bar as well as allow women to cross said pit on my back by creating a bridge. You might save the women, but those kids kids are toast if it's only you around to hear their screams.

Obiously in athletic activity, we may get into that movement....But who isn't ready for that movement? I have not done crunches in years and I can still flex my spine. Why do we need to train that movement more in the gym and why do we need to load it? If we are prepared properly, then we can achieve that movement without having to worry about it. You don't build stability at the expense of optimal mobility. All joints must have mobility before they can become stable. You can screen out lumbar mobility with standing toe touch and standing extension. If those movements are 'clean' I would have reason to believe that flexion shouldn't be a problem, but I don't need to go ahead and perform that movement in a training environment.

Like soxuscle said....chin ups are a great 'core' exericses. push ups too.

With regard to your second paragraph....why are you even asking me then? It sounds like you have made up your mind and you are content with your training program. You certainly don't need me to justify it. All I did was comment on not doing ab exercises and then people asked a few questions why. You are welcome to do whatever you want to do in your training program. I think the issues with things like hanging leg raises are that you can't get great pelvic position and control for the other factors to train what you really think you are training. I would much rather do the active straight leg lower progression as that trains what you think you are training, in an asymetrical sitatuation (like sprinting, running, walking) and allows you to focus on the other factors to ensure you get the biggest bang for your buck.

patrick
 
With regard to my ab shot....I don't have any pictures. I don't even care to take any. I am not a physique competitor or even interested in that type of stuff.

If you don't believe me, I don't care. You can come down to my facility and we can talk there. I'll give you a free assessment and we'll see how strong your core muscles really are. I can garuntee you that I have had people come in who do "tons of core" and can "hold planks for ever", only to have them end the assessment by saying "what happened? why can't I do any of this?"

patrick
 
You're really missing the point here.

:yes:

DB clean and press and db snatches seem to work the core pretty decently. Plus, they're way more fun then endless crunches anyway.
 
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Obiously in athletic activity, we may get into that movement....But who isn't ready for that movement? I have not done crunches in years and I can still flex my spine. Why do we need to train that movement more in the gym and why do we need to load it? If we are prepared properly, then we can achieve that movement without having to worry about it. You don't build stability at the expense of optimal mobility. All joints must have mobility before they can become stable. You can screen out lumbar mobility with standing toe touch and standing extension. If those movements are 'clean' I would have reason to believe that flexion shouldn't be a problem, but I don't need to go ahead and perform that movement in a training environment.

Like soxuscle said....chin ups are a great 'core' exericses. push ups too.

With regard to your second paragraph....why are you even asking me then? It sounds like you have made up your mind and you are content with your training program. You certainly don't need me to justify it. All I did was comment on not doing ab exercises and then people asked a few questions why. You are welcome to do whatever you want to do in your training program. I think the issues with things like hanging leg raises are that you can't get great pelvic position and control for the other factors to train what you really think you are training. I would much rather do the active straight leg lower progression as that trains what you think you are training, in an asymetrical sitatuation (like sprinting, running, walking) and allows you to focus on the other factors to ensure you get the biggest bang for your buck.

patrick

I don't recall asking you anything other than if you had a six pack. I'm simply disagreeing with the blanket statement of avoiding flexion movements altogether.

I don't have a whole paragraph of scientific research/explanation as to how I've come to my opinion, but simply this:
I've tried the advise (from this board) of eliminating flexion ab work and letting the compounds (weighted pulls/chins, push-ups, overhead/back squats, deads, etc.) and static exercises make up the difference. Did I have a six pack while doing this? Yup, as long as my BF% was low enough. Were they functional during this period. Yup. Were they as prominent, defined and as functional in my particular activities (beach v-ball, b-ball, freeclimbing, mtnbkng, mma), as when I incorporate low rep weighted flexion movements? Not even close.

I've no doubt you could design a physical assessment that I could not complete my first time, just as I'm pretty sure I could design one that I can do that you wouldn't complete, in fact I have a couple movements, that I doubt you could could complete one rep. Big deal. It's all about personal goals.

My point is, regardless of what the OP's goals are in asking his question about the bench, the advice of just "don't do flexion movements" and "avoid all direct ab work" (this one's for others), IMO isn't really optimal.

Oh and thanks for the permission to continue my regiment. I plan to.
 
Oh yeah, since I guess you guys missed it the first time, I agree on the crunches.
 
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If the diaphram doesn't work properly nothing else will. Breath is everything and is key to turning on the inner unit for adequate movement.

Yes, you do the same thing in sprinting (hip flexion)...but in an asymetrical stance. So, no, you do not do the same thing in sprinting at all.

Look, this is not my opinion. This is what the research says. If you are still doing crunches then you probably need read that research from the past 5 or 6 years.

patrick

Im not talking about crunches. They do really disturb my breathing pattern. I'm talking about hanging leg raises in conjunction with a pullup.

When you breath out, while going up, and you do the leg raise, your diaphragm is relaxed so I don't see how it would affect it. I certainly don't get affected, apart from the usual running short of breath in a pull up motion.
 
Im not talking about crunches. They do really disturb my breathing pattern. I'm talking about hanging leg raises in conjunction with a pullup.

When you breath out, while going up, and you do the leg raise, your diaphragm is relaxed so I don't see how it would affect it. I certainly don't get affected, apart from the usual running short of breath in a pull up motion.

If you think you can do them properly and you think they have value in your program then do them. I am not a fan, but if you can justify your position for doing them then go for it.

I just don't see a lot of people doing things right in the gym. I went and worked out at LA Fitness last night and 100% of the people there were doing nonsense - waste of time exercises, horrible technique, poor training programs, etc - It is my belief that most people don't know what they are doing. In fact, there are probably a lot of people on this site who think they know what they are doing, but upon closer inspection, they know very little.

All I can do (and my whole goal) is to give you the best information that I can based on what research says, empiricoal evidence and my opinion. When something is my opinion or based on empiricoal evidence, I let you know. When something is based on scientific research, I also let you know. I am not trying to pull the wool over anyones eyes. I don't have some strange ajenda. I don't even have a mass of products to sell, so it isn't like this is financially driven! I am driven and motivated by the fact that I spend my time studying this stuff because it is what I love. If I can share that with others and help them achieve their goals, then great. If you don't agree with something I am saying, then fine. Just have a good reason to do whatever it is you want to do. If you don't agree with something I am saying when I quoting research, then don't complain to me. Get on the phone and call or email the researchers and complain to them. I am merely telling you what their literature says.

patrick
 
If you think you can do them properly and you think they have value in your program then do them. I am not a fan, but if you can justify your position for doing them then go for it.

I just don't see a lot of people doing things right in the gym. I went and worked out at LA Fitness last night and 100% of the people there were doing nonsense - waste of time exercises, horrible technique, poor training programs, etc - It is my belief that most people don't know what they are doing. In fact, there are probably a lot of people on this site who think they know what they are doing, but upon closer inspection, they know very little.

All I can do (and my whole goal) is to give you the best information that I can based on what research says, empiricoal evidence and my opinion. When something is my opinion or based on empiricoal evidence, I let you know. When something is based on scientific research, I also let you know. I am not trying to pull the wool over anyones eyes. I don't have some strange ajenda. I don't even have a mass of products to sell, so it isn't like this is financially driven! I am driven and motivated by the fact that I spend my time studying this stuff because it is what I love. If I can share that with others and help them achieve their goals, then great. If you don't agree with something I am saying, then fine. Just have a good reason to do whatever it is you want to do. If you don't agree with something I am saying when I quoting research, then don't complain to me. Get on the phone and call or email the researchers and complain to them. I am merely telling you what their literature says.

patrick

Hey patrick, I'm here to learn. I just wanted to iron out any grey areas. Was just trying to find out if they will actually be harmful to me and for this I have to ask questions. I just want to find something I find comfortable but also I don't want to waste my time, or even worse, endanger my health later in life.

Is the flexion of the spine in such a way detrimental to the health of my spine? I have spine curvature and this is an area that I'm concerned about.
 
What literature are you referring to that concludes to avoid all flexion based movements?
I'm seriously interested, and not just trying to be an a-hole. Thing is, from what I can tell from the small amount I've researched on this subject, the conclusion to eliminate them entirely is an extreme reaction to the research.

Believe it or not, I do value your opinion and appreciate and believe that you are entirely unbiased and selfless in your advice. I have personally benefited from some of your counsel on this board, and for that I thank you. This doesn't change the fact that I disagree with you on this matter, and I know you could care less. I would be curious however to see the material you are drawing your conclusions from if you don't mind, but to be honest, I trust my own real world experience far more than a study of which I had no involvement in, especially when it comes to the fitness industry.
 
So most if not all at LA Fitness do movements wrong. Lots of people here that think they know better are doing moments wrong. What about the people in the studies?? lol

Anyhow, I guess it's to be expected that sit ups and such would need to be chastised. For years and years retarded ab products have been sold with false claims. Not surprising that research would swing in a direction totally against the common myths of the six pack.
 
T-man: It is the problem with repeated flexion of the spine. It is the cyclical pattern that we go through many times a day for years (that some of us then want to add into our gym program) that creates the pathological conditions and the wear and tear.

Jbish - The research I am talking about has been conducted by Dr. Stuart McGill at the University of Waterloo. He has a few books on the subject that highlight his research, as well as offer practical applications. In addition much of his research has been published in the Journal of Strength and Conditioning as well as other sources. Do you read the journals? There was actually a study just poublished (not by McGill) in Medicine and Science in Sports and Exercises that took military recruits and put half of them in a group who perfored traditional sit up training and the other half in a group that performed stabilization training (bridges, bird dogs, planks, etc). The groups had the same outcome in the military PT test. I was going to review the article for my blog one of these days.

Hoglander - I don't even know how to answer your question regarding people in the studies? Do you know how research is conducted? It isn't a free-for-all. They go through a process of teaching appropriate exercise technique for the given exercise prior to the study (a familarization period) and then the researchers ensure that this form is kept during the study. This is to allow others to replicate the study at a later date to further its validity to the field. This is just a bunch of people showing up and others watching to see what happens.

patrick
 
Another good exercise for abs (I find) is grab some pads and a medicine ball. Lie down and hold the medicine ball behind your head with your arms extended. Then, start doing a bicycle motion with your legs. Do not let your back come off of the pads - you will need to keep your core pretty damn tight all the time to pull that off. Try to do it for 20-30 seconds, rest, repeat.
 
Alternatives are fine. I think the video is good as well. I liked it when he genitally put his hands on her, kidding. There is nothing wrong with not doing sit ups. Just don't think they are that "SATANIC," IMHO.

: )
 
Thanks Patrick,
That helps to put things in perspective and actually solidifies my opinion on this topic. Here's why:
Near as I can tell, you are getting virtually all of your information from one source (as it all trickles back to Dr. mcgill), who unlike you DOES have an agenda as many sites quoting his studies link to his sales site to buy his media containing his new improved exercises.

Even then, I have have a hard time concluding from his research that he himself is condoning to completely eliminate all flexion motion as he mentions that it all depends on many factors, such as age, current core strength, history of injury as well as form. I can certainly respect the decision to simply suggest to eliminate flexion movements to those asking for advise on this forum as it's impossible to discern some of these factors online, but to conclude that it is optimal is off base IMO.

Here's a link that I found while researching Dr. Mcgill that explains the middle ground better than I've been doing. Hopefully the OP has gotten enough info to make an effective informed decision.
TMUSCLE.com | How to Build a Muscular Midsection
 
Thanks Patrick,
That helps to put things in perspective and actually solidifies my opinion on this topic. Here's why:
Near as I can tell, you are getting virtually all of your information from one source (as it all trickles back to Dr. mcgill), who unlike you DOES have an agenda as many sites quoting his studies link to his sales site to buy his media containing his new improved exercises.

Even then, I have have a hard time concluding from his research that he himself is condoning to completely eliminate all flexion motion as he mentions that it all depends on many factors, such as age, current core strength, history of injury as well as form. I can certainly respect the decision to simply suggest to eliminate flexion movements to those asking for advise on this forum as it's impossible to discern some of these factors online, but to conclude that it is optimal is off base IMO.

Here's a link that I found while researching Dr. Mcgill that explains the middle ground better than I've been doing. Hopefully the OP has gotten enough info to make an effective informed decision.
TMUSCLE.com | How to Build a Muscular Midsection

To me it's a simple question of risk versus reward.

Most of us are not trying to build mass monster olympia physiques, most of us simply want to have an athletic physique. You don't need to be doing thousands of super heavy weighted crunches to get that, you just need a bit of core work and a good diet.

Near as I can tell, there's only one sport that even consistently makes you repeatedly perform flexion and that's gymnastics (and even then it may not be that particular muscle group doing the work, I'm not an expert).

Why perform exercise(s) that can potentially cause serious issues for at best marginally better gains than what P-Funk is suggesting? That and if you never train your trunk for stability, how can you expect it to be stable when you need it to the most?
 
To me it's a simple question of risk versus reward.

Most of us are not trying to build mass monster olympia physiques, most of us simply want to have an athletic physique. You don't need to be doing thousands of super heavy weighted crunches to get that, you just need a bit of core work and a good diet.

Near as I can tell, there's only one sport that even consistently makes you repeatedly perform flexion and that's gymnastics (and even then it may not be that particular muscle group doing the work, I'm not an expert).

Why perform exercise(s) that can potentially cause serious issues for at best marginally better gains than what P-Funk is suggesting? That and if you never train your trunk for stability, how can you expect it to be stable when you need it to the most?

You're funny.
Did you read ANY of my previous posts? First off Who's talking about monster bodybuilding abs. I'm talking about what is the most optimal and effective way to train For BOTH function and physique. Patrick has stated he doesn't care about the latter, and I respect that, however from what I've seen on this board, especially from first timers, he's the minority.

My whole argument is that by NOT performing thousands although not entirely eliminating flexion work, you can achieve better results both in function and and physique. I've never said to not do what Patrick is suggesting for training abs (just the opposite actually), yet I am suggesting to increase the DYNAMIC nature of the routine by incorporating some key movements that done correctly and within proper weight training volumes will IMO not just minimally increase but greatly increase results, without adding any more danger to your spine, than doing a couple sets of heavy presses will do to your elbows, or squats will do to your knees. (there's research out on both these, but I believe we haven't eliminated them entirely).

If you really think Gymnastics is the only sport where this movement is made, you need to start playing more. I've mentioned a few previously, but it's obvious you didn't get that far.

I don't understand how you could assess minimal versus maximal results in this setting as you would need to achieve visible abs to even start to notice a difference at least physique wise, and at higher than 10% BF I'm doubting you've acheived that.
 
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patrick, it isnt worth it anymore. dont raise your BP ;)
 
Urbanski, my blood pressure is not rising (haha). I enjoy debate and when it comes to the application of research, there certainly can be a lot of it.

Anyone can read a study and read research and come to their own conclusions. This is why I encourage others to sit down and read the literature. jibish8, have you read Dr. McGill's book? He cites other sources behind his own to show where his thought process came from. It isn't like he just made it up. He is the one that is kind of "pushing" the movement, I guess you could say.

Like Danzik said, this is a case of risk vs. reward.

With any exercise, there is a risk vs. reward. It is not my job to judge anyone on the exercises they choose in their training menu, as you will have a different risk vs. reward than I will and I will have a different risk vs. reward than someone else.

When you look at the literature on flexion of the spine, especially repeated flexion of the spine (as occurs in daily life - lifting things off the floor, moving around, sitting in a desk all day), the question that I then come to is, "why do I need to do more of this in the gym?" People are always felxing (whether it is right or wrong, or whether it is occuring for other reasons - improper biomechanics, poor hip mobility, etc...). So, I would rather go and train other factors in the gym, to help develop the muscular in a stabilizing role.

Anyway, to show I am not bias to McGill, here are some studies on repeated or prolonged flexion (IE, sitting in a desk all day)and the spine, and the flexion-relaxation phenomenon (which discusses why this position places us at a greater potential for injury). You can take this information and do what you want to do with it.

But, if you are going to argue, please provide some research to support your conclusions. I have said before, you can do whatever you want in your own training program or your own program with your clients/athletes. However, you need to fully explain why you are doing something, what purpose it serves and what you have read to come to that conclusion.


Flexion-relaxation response to cyclic lumbar flexion

Michael W. Olsonabc, Li Liac, Moshe Solomonowabc

Volume 19, Issue 8, Pages 769-776 (October 2004)

Background. The epidemiology classify cyclic lumbar flexion as a risk factor for the development of cumulative low back disorder. Experimental biomechanical data confirming the epidemiology in humans are lacking. The purpose of this study, therefore, is to investigate the flexion relaxation response to sustained cyclic lumbar flexion in humans.

Methods.
Twelve normal college aged males performed deep cyclic lumbar flexion at 0.1 Hz for 9 min while recording lumbar paraspinal electromyogram and kinematic data.

Findings. The most important observation of the study was the significant increase in the angular excursion of myoelectric silence during the deep part of the flexion phase. The observed increase in myoelectric silence consisted of earlier cessation of EMG during flexion and delayed activation of trunk extensors during extension. EMG magnitude, during flexion, increased approximately 30% over trials (P<0.0001), and a smaller (10%), but, significant (P<0.02) EMG magnitude increase was also observed during the extension phase of the cycle. Spasms, an indication of micro damage to viscoelastic tissues, were sporadic and appeared more frequently later in the session and mostly during the silent period.

Interpretations. It was concluded that increased myoelectric silence during prolonged cyclic flexion-extension demonstrates an enhanced flexion-relaxation phenomenon which reduces lumbar stability and may be detrimental to low back health. The presence of spasms confirm that sustained cyclic lumbar flexion results in micro damage in the viscoelastic tissues. Overall, a neuromuscular disorder was evoked due to a relatively short period of unloaded cyclic lumbar flexion.

Changes in the flexion relaxation response induced by lumbar muscle fatigue.

BMC Musculoskelet Disord. 2008 Jan 24;9:10.

Descarreaux M, Lafond D, Jeffrey-Gauthier R, Centomo H, Cantin V.

BACKGROUND: The flexion relaxation phenomenon (FRP) is an interesting model to study the modulation of lumbar stability. Previous investigations have explored the effect of load, angular velocity and posture on this particular response. However, the influence of muscular fatigue on FRP parameters has not been thoroughly examined. The objective of the study is to identify the effect of erector spinae (ES) muscle fatigue and spine loading on myoelectric silence onset and cessation in healthy individuals during a flexion-extension task.

METHODS:
Twenty healthy subjects participated in this study and performed blocks of 3 complete trunk flexions under 4 different experimental conditions: no fatigue/no load (1), no fatigue/load (2), fatigue/no load(3), and fatigue/load (4). Fatigue was induced according to the Sorenson protocol, and electromyographic (EMG) power spectral analysis confirmed that muscular fatigue was adequate in each subject. Trunk and pelvis angles and surface EMG of the ES L2 and L5 were recorded during a flexion-extension task. Trunk flexion angle corresponding to the onset and cessation of myoelectric silence was then compared across the different experimental conditions using 2 x 2 repeated-measures ANOVA.

RESULTS: Onset of myoelectric silence during the flexion motion appeared earlier after the fatigue task. Additionally, the cessation of myoelectric silence was observed later during the extension after the fatigue task. Statistical analysis also yielded a main effect of load, indicating a persistence of ES myoelectric activity in flexion during the load condition.

CONCLUSION: The results of this study suggest that the presence of fatigue of the ES muscles modifies the FRP. Superficial back muscle fatigue seems to induce a shift in load-sharing towards passive stabilizing structures. The loss of muscle contribution together with or without laxity in the viscoelastic tissues may have a substantial impact on post fatigue stability.

Repeated spinal flexion modulates the flexion-relaxation phenomenon.

Dickey JP, McNorton S, Potvin JR.

Clin Biomech (Bristol, Avon). 2003 Nov;18(9):783-9.

OBJECTIVES: To determine if repeated spinal flexion and loading modulate the deactivation of lumbar muscles near full flexion (flexion-relaxation).

DESIGN: Repeated measures experimental study of the effect of repetitive trunk flexion and added mass on the flexion-relaxation phenomenon.

BACKGROUND: Repeated flexion causes muscular fatigue, creep of passive tissues and diminished protective reflexes. However, flexion-relaxation has not been studied in repeated trunk flexion, and could be related to the increased risk of low-back disorders.

METHODS: Thirty healthy young subjects performed 100 trunk flexion movements between standing and full flexion. Erector spinae electromyography and lumbar spine flexion were measured during cycles 1-10 (no load), 11-20 (performed holding a mass in the hands), 81-90 (mass in the hands) and 91-100 (no load). The spinal flexion angle at myoelectric silence and full flexion were extracted from each movement cycle.

RESULTS: Twenty-three of the 30 subjects showed flexion-relaxation throughout the repeated trunk flexion. The flexion-relaxation and maximum flexion angles increased at the end of the experiment; the flexion-relaxation angle relative to the maximum flexion angle also increased. This effect depended on the load condition; the flexion-relaxation and maximum flexion angles showed a greater increase in the unloaded than loaded condition.

CONCLUSIONS: The flexion-relaxation phenomenon was changed due to repeated trunk flexion. The increases in flexion-relaxation angle likely involve changes to the neuromuscular control system.

RELEVANCE: The deactivation of the erector muscles near full flexion occurs at a greater spinal flexion angle and a greater proportion of maximum spinal flexion following repeated spinal flexion. This may be related to the increased risk of injury associated with repeated flexion.

An in vivo assessment of the low back response to prolonged flexion: Interplay between active and passive tissues.

Shin G, Mirka GA.

Clin Biomech (Bristol, Avon). 2007 Nov;22(9):965-71. Epub 2007 Aug 20.

BACKGROUND: Full flexion lumbar postures maintained over a prolonged period of time have been shown to lead to changes in the supporting passive structures of the spine and it has been hypothesized that this may lead to low back pain/disorders. However, the specific biomechanics and physiology of this link have not been fully developed. Of particular interest is the interplay between the active and passive extensor mechanisms and the role of rest break in this response.

METHODS: Ten healthy participants performed a regimen of a 10-min full lumbar flexion followed by a 10-min upright standing, with a slow speed isokinetic lift every 2.5min. Changes in the full lumbar flexion angle (system creep) and the electromyographic activity of back extensors in the isokinetic lifts were evaluated.

FINDINGS: Results showed significant increases in the full flexion angle and increased activity of the extensor muscles in the prolonged flexion to compensate for the reduced extension moment producing capability of the passive tissues. A 30-s rest break in the middle of the flexion moderated these viscoelastic responses.

INTERPRETATION: The results suggest that prolonged lumbar flexion results in the systematic transfer of an extension moment from passive tissues to active muscles. Heavy lifting or high force exertion of back muscles immediately after prolonged flexion could be a risk factor for low back disorders when the muscles lose their force generating capacity due to passive stretching. This study also indicated the importance of sufficient rest between consecutive full flexion tasks in reducing the risk.

patrick
 
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