Home Posts tagged "Recovery"

Elite Baseball Development Podcast with Brandon Marcello

We're excited to welcome sports scientist Dr. Brandon Marcello to the podcast for Episode #14 for an in-depth discussion on sleep. A special thanks goes out to this show's sponsor, VersaPulley. It's an awesome option for challenging deceleration in multiple planes of motion, and has been an excellent addition to our training at Cressey Sports Performance. They've got a great 10% off offer going for our podcast listeners at http://www.VersaPulley.com/Cressey10.

Show Outline

  • What the four major components of recovery are, and how sleep influences these domains
  • Why sleep is vital for human performance and what the negative implications are for ignoring its importance
  • How individuals are actually born as early birds or night owls, and what strategies people should utilize to maximize their sleep regardless of their tendencies
  • Why routine is king when establishing quality sleep habits
  • What is sleep debt and why it is significant for people to avoid the accumulation of sleep debt over time
  • How impactful are naps for overcoming the accumulation of sleep debt, and how to best incorporate them
  • Why not all sleep supplements are everything they claim to be
  • What easy adjustments athletes can implement to improve their sleep beyond the well-known strategies already commonly practiced
  • How athletes can combat the negative implications of their current sleep situation
  • Why coaches should encourage their athletes to value their sleep, and what strategies they can use to aid in their players accumulation of quality sleep

You can follow Brandon on Instagram at @bmarcello13 and Twitter at @bmarcello13.

Sponsor Reminder

This episode is brought to you by VersaPulley. The VersaPulley offers flywheel training and one benefit of training with a flywheel is inertia. The faster the flywheel is moving, the more the user must decelerate the inertia that is created - and we know training deceleration is a huge piece of preventing athletic injuries and enhancing performance. While there are a few flywheel training options on the market, the VersaPulley is the only one that that allows you to train at any point along the force/velocity curve, and in multiple planes of movement. If you want to train at any speed, any load, and any direction, the VersaPulley has got you covered. They've set up a great discount of 10% for our listeners; you can learn more at http://www.VersaPulley.com/Cressey10.

Podcast Feedback

If you like what you hear, we'd be thrilled if you'd consider subscribing to the podcast and leaving us an iTunes review. You can do so HERE.

And, we welcome your suggestions for future guests and questions. Just email elitebaseballpodcast@gmail.com.

Thank you for your continued support!

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Cryotherapy and Exercise Recovery: Part 1

Today's guest post comes from Tavis Bruce. A while back, I asked Tavis to pull together an article examining the literature on cryotherapy with athletes, and as you'll see below, he really overdelivered. Enjoy! -EC

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Sports and ice go together like peanut butter and jelly (or steak and eggs, if you’re into Paleo). From ice packs to ice baths, various forms of “cryotherapy” have long held a sacred place in sports medicine to treat acute injuries and facilitate recovery from training or competition. But despite its popularity and widespread use, the evidence in support of cryotherapy remains equivocal.

More recently, cryotherapy—particularly the use of ice baths, or cold water immersion—has come under increasing scrutiny from both the scientific community and the strength and conditioning industry at large...and rightfully so! However, in the process, we may be swinging the pendulum too far in the other direction, indicated by those who have come to the conclusion that “ice baths are a complete waste of time for every athlete in every sport in every possible situation.” Now, others may disagree with me on this one; but, the evidence (or lack thereof) for cryotherapy appears to be a little more nuanced than that.

I guess what I’m trying to say is: I’m not so sure I’m ready to throw the ice out with the bathwater just yet. Perhaps, instead of pondering black-and-white questions like, “to ice or not to ice?” we should be asking:

                         “When is ice appropriate?”

I’d like to examine why.

A quick note before we get started: this article will not discuss the use of cryotherapy for the management and/or rehabilitation of acute soft tissue injuries. I am NOT a medical professional; I just play one on Facebook.

As such, this article will only cover the efficacy of cryotherapy as a post-exercise recovery strategy.

Is there a Physiological Rationale for Cryotherapy?

Note: I’m not going to spend much time discussing the physiological rational (the “why”) behind cryotherapy for two reasons. First, the mechanisms are still quite hypothetical. Second, and more importantly, it’s a bit outside the scope of this article to convey practically relevant and actionable information for my fellow coaches and athletes. We can debate the mechanistic stuff until the cows come home, but in my humble opinion, the gold standard measurement for post-exercise recovery is the measurement of performance variables. And, I like to think that most athletes, coaches, and sports scientists would agree with me. That being said, I do think it’s always a good idea to establish if there is at least a physiological rationale for any method we may use with ourselves and/or our athletes. With that said…

Cryotherapy results in various physiological changes (most of which are temperature-dependent) that have long been proposed to exert a therapeutic effect post-exercise. Although the most cited physiological change is a blunted inflammatory response, there exists a range of other effects through which cooling the body after exercise may accelerate the recovery process. Of note, cryotherapy may:

• Improve tissue oxygenation1 and removal of metabolic waste (2) by reversing exercise-induced muscle edema (3,4).
• Reduce reactive oxygen species (ROS)-mediated muscle damage (5) by reducing local metabolism (1).
• Induce analgesia by decreasing nerve conduction velocity (6) in addition to directly activating sensory afferents (7).
• Restore parasympathetic tone by increasing vagal tone (8,9).

In addition, cold water immersion (or “ice baths”), a popular form of cryotherapy, may have additional benefits resulting from the compressive forces experienced during water immersion, but I won’t be covering them in this article (see Wilcock et al. [10] for a good review). For more information on the physiological effects of cold water immersion and other forms of cryotherapy, I encourage you to check out this (open access!) review by White and Wells.

The Effects of Cryotherapy on Recovery from Sport or Exercise

Perceptual Measures of Recovery

Cold water immersion reduces perceptions of fatigue (11-16) and increases perceptions of recovery (17,18) and physical readiness (19) between training sessions; however, it doesn’t seem to have much of an effect on ratings of perceived exertion (RPE) during subsequent training bouts (20-23).*

*Except for when CWI is used as a precooling strategy before exercise. (More on precooling later.)

Delayed-Onset Muscle Soreness

Though it’s pretty well accepted that cooling injured tissue can temporarily reduce or relieve pain (24), it’s not really clear if post-exercise cooling has any effect on delayed-onset muscle soreness (DOMS): the type of soreness you feel in the days following a bout of intense or novel exercise.

There is some evidence that cold water immersion (CWI) alleviates DOMS better than passive recovery (25), particularly when CWI is used following exercise that involves a large degree of metabolic stress (26) (e.g., running, cycling, or team sports). However, this effect is less clear when CWI is compared to warm (27), thermoneutral1 (4,28), or contrast (27,29,30) immersion, and recent evidence suggests that CWI may be no more effective than a placebo (19) for relieving DOMS. Collectively, these findings highlight the perceptual nature of muscle soreness and the importance of athletes’ perceptions of cryotherapy (or any recovery method, for that matter).

Icing and cold water immersion may help reduce delayed-onset muscle soreness after running or team sports, but the effect likely depends on the athlete’s belief in cryotherapy as a method of recovery.

Range of Motion

There is conflicting data on the effect of cooling on range of motion (ROM). Cooling alone does not appear to improve ROM (28,31-38), but it may enhance the effects of stretching (39-43) by increasing stretch tolerance (44). On the one hand, this increased tolerance to stretch does not appear to translate into long-term improvements in ROM (45-47). On the other hand, heat combined with stretching may have more lasting effects than stretching alone (44).

If your goal is to restore lost ROM following exercise, combine heat (not cold!) with stretching.

GoodHFStretch

Strength

The short-term effects of post-exercise cooling on recovery of strength characteristics are mixed and seem to depend on the type of exercise stress from which you’re trying to recover before you hit the weights.

There is some evidence that CWI may reduce or recover losses in maximal voluntary contraction (MVC) following simulated team sports (48-50) or intermittent sprint exercise (51-53), but not after downhill running (54) or cycling (55,56). And, in the only study of its kind, Broatch et al. found that CWI following high-intensity sprint intervals recovered MVC no better than a thermoneutral placebo (19).

Roberts et al. demonstrated that CWI was effective for restoring submaximal (but not maximal) strength between two lower body training sessions within the same day (57). Vaile et al. found both cold and contrast water immersion were effective at restoring strength up to three days after heavy eccentric strength training (27)*, but most studies show no or non-significant improvements over this time period (28,58-62). However, it’s important to note that all of these studies used (potentially) “less effective” cooling methods (such as when only the exercised muscle is cooled) compared to more therapeutic methods such as whole-body CWI.

*I highlight the study by Vaile et al. because it is the only study that compared multiple hydrotherapy modalities in trained males, and in a cross-over design with a “washout” period between treatments of sufficient duration to eliminate any residual effects of the repeated bout effect. Thumbs up for study quality!

Cold water immersion may help recover muscle contractile properties following running or team sports. Benefits following resistance training are less clear and may require the use of cold water immersion over local cooling of exercised tissue.

Jump Performance

Most studies show significant recovery of jump performance within 24-48 hours post-exercise with no clear additional benefits to CWI (18,49,53,63,64). Furthermore, CWI may impair jump performance within the first two hours (57) possibly due to the acute effects of cold exposure on force production (65).

Here’s the deal: jump performance seems to recover just fine on its own. However, there is some evidence that CWI may maintain jump performance in scenarios of accumulated fatigue, such as during tournament play in team sports. One study of basketball players found that the CWI maintained jump performance better in players who saw more playing time throughout a 3-day tournament (66).

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Sprint Performance

Like jump performance, many studies report that sprint performance returns to baseline within 24 hours after exercise, regardless of treatment intervention (18,49, 61). Accordingly, most studies do not find a benefit in favor of CWI compared to other recovery interventions because the initial exercise bout was not sufficiently intense to elicit a significant 24-hour performance decrement.

However, when exercise was sufficiently intense to affect 24-48 hour sprint performance, CWI maintained repeat-sprint performance (a measure of speed-endurance) better than thermoneutral immersion (67), contrast water therapy (12,13,48), and passive recovery (12,13,48,67).

The effect of CWI on absolute speed is less clear. Of the two studies I found, one found no benefit to CWI over passive recovery on immediate and 24-hour recovery of 50-m dash time (68), while the other showed that CWI maintained 20-m speed better than compression or stretching over a 3-day simulated basketball tournament (66).

There’s not a lot of data on the effects of CWI on same-day recovery of sprint performance, but one study showed no significant differences in repeat-sprint performance between CWI and passive recovery immediately and up to two hours after intermittent sprint exercise in the heat (61). This ties in well with the research in sprint cycling that shows neutral—or even detrimental—effects on 30-second Wingate performance following CWI when sufficient re-warming does not occur (69,70). This makes sense: reduced muscle temperature will negatively affect muscle contractile properties (71), impair energy metabolism (72), and slow nerve conduction velocity (6,73), which collectively will negatively affect the force- and power-generating capabilities of muscle. Thus, caution should be taken when using CWI between or prior to exercise that requires a high-degree of muscular force (sprinting, jumping, etc.). Athletes should allow sufficient time to rewarm following CWI and make sure to include a dynamic warm-up before their next event, which has been shown to offset the negative effects of cold exposure on power production in the vertical jump (65).

When exercise is sufficiently intense, CWI may help restore short-term (<48 hour) sprint and jump performance. However, reduced muscular temperatures negatively affect the force-generation capacities of muscle. Thus, when using ice baths between two training sessions or events within the same day, it is important to allow the body sufficient time to re-warm and/or to include an extensive dynamic warm-up.

Endurance Performance

Given the number of endurance athletes that use ice baths to recover between workouts or events, it was somewhat surprising that very few studies looked at endurance performance following recovery periods of 24 hours or longer. Two of those studies showed that CWI improves endurance performance following a 24-hour recovery period (17,74), and two other studies demonstrated similar recovery benefits across 3-day (75) and 5-day (23) training blocks.

Paula_Radciffe_NYC_Marathon_2008_cropped

Most studies that looked at the effects of CWI on recovery from endurance exercise utilized recovery periods of <60 minutes between exercise bouts. But here’s the thing: When an athlete takes an ice bath between two bouts of exercise with a short (<1 hour) duration between bouts that ice bath creates a “precooling” effect for the second bout. Precooling is proposed to increase performance (particularly in hot conditions) by increasing heat storage capacity, reducing thermal strain, and decreasing perceived exertion by reducing core body temperature prior to exercise (76).* And, based on the abundance of data showing a benefit to precooling on endurance performance** (particularly in hot conditions), this is probably why we see such an immediate recovery of endurance performance following CWI (56,77-81). This effect diminishes with longer recovery periods (82), presumably as core body temperature returns to baseline.

*If you’re interested in learning more about precooling check out this (open-access!) systematic review as well as the results of two recent meta-analyses here and here.

**Just to reiterate: the beneficial effect of precooling likely does not hold true for short-duration, maximal efforts (see above).


Ice baths may be useful for recovering endurance performance, particularly when an athlete has to compete in multiple games or events in one day.

The Effect of Regular Cold Water Immersion on Long-Term Training Adaptations

Very few studies have looked at the effects of ice baths on long-term training adaptations. But, the evidence-to-date paints a pretty clear picture:

Strength Training

The evidence is pretty clear on this one: regular use of CWI impairs long-term gains in muscle mass and strength (83-86) at least in part by blunting the molecular response to resistance exercise (84). This seems to apply to both trained (84) and untrained (85,86) individuals.

Ice baths blunt the acute molecular response to resistance training and impair long-term gains in muscle mass and strength. Athletes should reconsider using ice baths after strength training, particularly in the off-season or preparatory period when the focus is on adaptation rather than performance.

Endurance Training

The evidence for the effects of CWI on adaptations to endurance training is not so clear. One study in competitive cyclists found that regular CWI neither enhanced nor interfered with cycling performance over a three-week training block (87). Furthermore, recent evidence suggests that regular CWI may actually enhance molecular adaptations to endurance training (88). However, it’s important to interpret these results with caution, as molecular adaptations do not always reflect functional outcomes and the study did not measure changes in performance. Of note, there is some evidence that regular CWI at very cold temperatures (5ᵒC) for very long durations (>30 minutes) may disrupt local vascular adaptations and attenuate improvements in VO2max to endurance training in untrained subjects (85).

There is no direct evidence to suggest that ice baths enhance nor interfere with endurance training adaptations. In trained athletes, ice baths can be used sparingly after endurance training, but regular use is not recommended, particularly during the preparatory period when the focus of training is on adaptation. Finally, ice baths of excessive duration or at extremely cold temperatures should be avoided.

Major Take-Aways

The evidence for cryotherapy is pretty mixed, but there are some patterns that seem to emerge from the literature:

• Cold water immersion and other forms of cryotherapy reduce exercise-induced inflammation.
• This reduction in inflammation may lead to reduced perceptions of fatigue and muscle soreness and increased perceptions of recovery which may benefit performance in the short-term.
• Importantly, the short-term recovery benefits of cryotherapy may depend considerably on the mode exercise (i.e. the type of stress), the physiological and perceptual qualities one is trying to restore, and (as I will discuss further in Part 2) the athlete’s belief in cryotherapy as a recovery modality.
• Meanwhile, a growing body of evidence indicates that inflammation is a necessary process for tissue regeneration and, as such, regular use of cold water immersion may impair long-term muscular and vascular adaptations to exercise.
• As such, cryotherapy should be used sparingly, particularly in the off-season when the goal is to maximize training adaptations.

In Part 2, I will address:

• whether baseball pitchers should ice their arms
• whether there an optimal cooling method, temperature, or duration
• whether cryotherapy is just one big fat placebo
• practical recommendations for athletes and coaches

Stay tuned for Part 2!

Note: the references for this entire article (including the upcoming part 2) will be posted as the first comment below.

About the Author

A native of the Great White North, Tavis Bruce (@TavisBruce) is no stranger to the effects of cold on athletic performance. He holds a Bachelor of Kinesiology and Health Science from the University of British Columbia, where he pitched for the Thunderbirds baseball team for three seasons. Tavis is currently the Director of Education for the Baseball Performance Group, where he integrates his passion for sports science with his love of baseball. He can be contacted at tavis.bru@gmail.com.
 

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Strength and Conditioning Stuff You Should Read: 3/23/15

Good morning, gang. I hope you all had a great weekend. We're going to kick off the week with some recommended strength and conditioning reading from around the 'net:

Settling the Great Grain Debate - My good friend and former Cressey Sports Performance coach Brian St. Pierre did a fantastic with this review for Precision Nutrition.

bspphoto

Is it time to turn our attention toward central mechanisms for post-exertional recovery strategies and performance? - This is a science-heavy but outstanding article that was recently published in Frontiers in Physiology. It'll be required reading (and discussion) for an upcoming in-service at our facility.

Want to Get Strong? Quit Switching Training Programs Every Week. - As the title implies, this old article of mine begs readers to stay on programs long enough to actually evaluate if they work.

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3 Considerations for the Aging Athlete

At Cressey Performance, we’re largely known for our work with baseball players, but that’s not to say that we don’t have our fair share of “weekend warriors” – those who like to get after it in the gym well into their 40s, 50s, and 60s – in the mix.  With that in mind, we haven’t done a great job of reflecting this in our online content, so we’re going to start to remedy that today!  In today’s post, CP coach Greg Robins introduces his top three recommendations for the aging athlete. -EC

1. Seek out a professional evaluation.

Without fail, we are approached daily at Cressey Performance by individuals looking for our “pitchers” program, our “strength” program, or any other number of set approaches to dealing with one type of scenario. The truth is, we don’t have those lying around anywhere. Instead of writing “outcome-specific” programs, we write “athlete-specific” programs. Where am I going with this?

There is no “older athlete” specific program. There are only trends in training older athletic populations that must be considered when evaluating them, and then writing their programs. To be honest, the older athlete needs this attention to detail moreso than many of the younger athletes we see at CP. Why?

It’s simple, really: older athletic populations have accumulated decades of the same repetitive movements, on top of a growing list of nagging injuries, serious injuries, aches, pains, and so on.  

If injury is derived from this equation…

 

 Number of repetitons x Force of each repetition

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Amplitude of each repetiton x Relaxation between repetitons

 

…then you can imagine just how much higher the figure for “N” has grown in comparison to their considerable younger counterparts.  And, keep in mind that degenerative changes kick in easier and linger longer as we age.

In short, the first and most important consideration for the older athlete is to have their movement evaluated by a qualified professional so as to formulate a safe and productive plan of action for training. Without this information exercise selection becomes a shot in the dark, rather than a well formulated choice of movements to meet the person where they are at.  For those looking to self-evaluation, Assess and Correct would be a good a great DVD set to review.

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2. Improve your recovery.

Aging populations will find that their ability to recover from bouts of intense exercise has steadily diminished as they age. Therefore, recovery measures must take a front seat in their approach to getting better while staying healthy. These populations should place a premium on the standard sources of improved recovery, namely sleep and nutrition. However, I would like to touch upon another factor, often neglected, that can help tremendously in the older athlete’s approach.

Aerobic capacity, or improved aerobic fitness, will be paramount to their success. Your body runs on three main energy systems:

  • Aerobic
  • Anaerobic
  • ATP – PCr

When it comes down to producing energy, the body’s currency is ATP. All of these energy systems are channels for producing the currency of your body’s energy. Each has their way of doing so, and each does so in a different context.

Many of us associate aerobic exercise with long duration activities, and therefore a long duration of ATP generation. We see anaerobic exercise as short duration, and therefore, a short duration of ATP generation. In short, that’s mostly correct. You can view ATP-PCr as an even shorter duration generation that the anaerobic energy system. While ATP-PCr, and the anaerobic energy systems are capable of producing a lot of ATP quickly, they also run out of currency quite fast as well.

The facilitation of the aerobic energy system is important because it’s always in play. In other words, the better trained it is, the more ATP it is generating for you over the course of the entire bout of exercise. This leads to better ATP production in general – in the short term, the ability to repeat the short term, and the long haul in total. That’s important to the older athlete, and any athlete for that matter.

Need proof that it matters? Here’s a 2001 study showing a positive correlation between aerobic fitness and recovery from high intensity bouts of exercises published in 2001.

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To take it a step further, a well-conditioned aerobic system doesn’t just help you recover during the workout; it also helps you to recover between workouts, faster! It plays a large role in giving you the energy required to repair, and helps you to “switch” into your autonomic nervous system, which is optimal for increased recovery.

I highly recommend you read further on how this relationship plays out, how to train it, and how to evaluate it by reading Mike Robertson’s article here. Also, you’ll benefit from checking through the lengthy list of information and tools from Joel Jamieson.

3. Manage Volume Better.

If we take into account our first two bullet points, then it’s important that we address training volume in general. Mismanaged training volume can accelerate the equation in our first point, as well as hinder our recovery efforts laid out in point number two.

In general, aging athletes will need to be more cognizant of the total work they are doing and its effect on their outputs. A positive in training this population is that they have spent considerably more time listening to their body. This is important, and should not be disregarded. Instead of blindly following any program, I would urge the older athlete to learn from past experiences and back down when their body is telling them to do so. Many times, the more experienced the athlete; the better they are at doing this.

Additionally, I would challenge the older athlete to deload, or “back off” more often. This is an easy way to manage the volume of training in their favor. Many programs will load for 3-4 weeks and then unload for one. However, older athletes can benefit from cycling in periods of backed down volume and intensity more often. Here are two such scenarios.

  1. High / Low Organization

High – Low organization is among my favorite ways to train an older athlete. It was developed originally to train very high-level athletes to ensure top outputs every time they train. By getting a high output one week, and then letting them recover the next week, there was much less chance of accumulating fatigue, and having the athlete continually training at something less of what they were actually capable of achieving. This gave them a chance to repeat high outputs more often, as well as top those efforts.

It makes sense in the training of older athletes as well. In a similar fashion to these high-level trainees, high outputs will take a lot out of the tank for the older populations. Since our goal is still to improve the performance of older athletes, while minimizing injury, this is a great approach.

  1. High / Medium / Low Organization

This is another solid option. In this example we are loading an athlete for two weeks, and then unloading them for one. The first week would be high intensity; the second medium (with slightly more volume), and the third week low in both intensity and volume. It’s basically a play on the first example, and can be used for an older athlete who may be able to handle more volume. It’s also a better choice for the older strength athlete who will need the second week of increased volume to continue making progress on the lifts, as well as the technical practice of performing the lifts under decent load more often.

If you’re looking for more deloading strategies, I’d encourage you to check out Eric’s e-book on the subject: The Art of the Deload.

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In conclusion, the older athlete needs to place a premium on correct movement, recovery measures, and management of volume or training stress. With those three considerations in mind, there is lots of room for improvement at any age!

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Strength and Conditioning Stuff You Should Read: 11/4/13

Here's is some strength and conditioning reading (and viewing) to kick off your week:

5 Tips to Keep Your Shoulders Healthy for the Long Haul - This is a guest post I wrote up for Greatist.com.

ECtable

Dreaming of a Title - In light of the World Series run by the Red Sox, CP's Elite Baseball Development Program was featured, with interviews with several of our pro guys.  Check out this video.

Boosting Recovery: Solutions to the Most Common Recovery Problems - This was an outstanding guest post by Examine.com's Kurtis Frank at Precision Nutrition.

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T-Nation Strength and Size Roundtable: Part 3

Writer Greg McGlone rounded up five of the biggest, baddest, strongest, and best-informed hombres in the iron game, and invited them to share their "secrets" with those of us who also want to get bigger, badder, stronger, and better-informed. In part 1, the coaches discussed the viability of building size and muscle at the same time, along with a comparison between compound and isolation movements. In part 2, they tackled the topic of whether you have to look strong to be strong, along with a fascinating discussion of training splits. Today, the topics include nutrition, supplementation, recovery, and some final thoughts. Continue Reading
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Adrenomedullary Enlightenment

Sometimes, you need to be smart just for the sake of being smart. With that in mind, I present to you the first paper I wrote as a graduate student. While it undoubtedly made me a more informed researcher and student, it's still one week of my life that I'll never, ever get back. Enjoy. Introduction The adrenal medulla is well known as a powerful modulator of the physiological response to both exercise and rest via the "Fight-Flight" response. However, in light of opioid peptide research over the past few decades, it is now quite clear that the adrenal medulla plays a more prominent role than was originally perceived. Now, the study of adrenal medullary secretory activity, which was once limited to the catecholamines epinephrine, norepinephrine, and dopamine, also encompasses the lesser understood proenkephalin family of opioid peptides. With that in mind, it is important to consider adrenal medullary response to exercise stress and subsequent recovery in a broader sense. The Catecholamines and Adrenomedullary Activity Before considering the widespread impacts of the catecholamines in relation to exercise, it is important to note the relative contributions of each. Norepinephrine secretion from the adrenal medulla is certainly a contributing factor to the overall sympathoadrenal-medullary response to exercise, as the plasma concentration of the hormone (which also acts as a neurotransmitter) can increase twenty-fold with high-intensity exercise (1). However, sympathetic nerve endings also directly secrete norepinephrine to target tissues; during exercise, roughly 50% of total norepinephrine secretion occurs in the active muscles (2). Dopamine is the first catecholamine formed after the conversion of tyrosine to dihydroxyphenylalanine (dopa), the common chemical precursor for the three catecholamines. Norepinephrine and epinephrine are formed thereafter from this same pathway (3-5). Dopamine is present in the adrenal medulla and cortex, kidneys, peripheral nerves, carotid body, and sympathetic ganglia (6). In fact, it is the most abundant catecholamine in human plasma (5). However, only 2% exists in the free form; the remainder consists of biologically inactive metabolites (5,6). And, though the plasma free form dopamine concentration rivals that of epinephrine (and 20% of norepinephrine), it is not capable of the magnitude of physiological effects seen with epinephrine and norepinephrine (6). As such, although dopamine certainly plays a role in the adrenomedullary cascade of events in response to exercise, it is a less utilized measure of adrenomedullary activity during exercise and in recovery. Although dopamine is the most abundant catecholamine in the blood, epinephrine constitutes the vast majority of adrenal-medullary catecholamine release. Shah et al. proposed that those tissues outside of the CNS that produce catecholamines be labeled the "sympathochromaffin system," and be divided into two components: the sympathetic nervous system (neurotransmitter norepinephrine from postganglionic neurons) and the chromaffin cells (which secrete epinephrine, norepinephrine, and/or dopamine) (7). In short, plasma norepinephrine concentrations best quantifies sympathetic neuronal activity, whereas plasma epinephrine concentration is the optimal index of adrenomedullary secretions of catecholamines (7). With all these factors in mind, one can surmise that changes in plasma free epinephrine concentrations serve as the measure of choice in the discussion of the adrenomedullary catecholamine response to exercise and subsequent recovery. Catecholamine Response to Exercise Various intensities, durations, and modes of exercise serve as powerful stimuli to the adrenal medulla to initiate the Fight-Flight response. Numerous studies have found that epinephrine and norepinephrine secretions increase as exercise intensity increases. For instance, Kraemer et al. found that plasma epinephrine (Figure 1) and norepinephrine steadily increased during graded exercise on a bicycle ergometer from 54% to 83% and 100% of maximum oxygen consumption (VO2 max) in both trained and untrained subjects (8). Others have verified this relationship between plasma catecholamines and intensity during graded exercise sessions regardless of training status (9-12). Designation of a specific exercise intensity at which the adrenomedullary activity becomes significant is yet to occur, as catecholamines are always at work in the body. Unloaded cycling at approximately 10% VO2 max did not increase plasma catecholamines above resting values in young men (13). Likewise, as demonstrated in Figure 1, graded exercise on a bicycle ergometer did not increase plasma epinephrine above baseline at 54% VO2 max (8). However, Greiwe et al. demonstrated that norepinephrine and epinephrine (Figure 2) both increased with each 5% increment from 60% to 85% VO2 max before and after ten weeks of endurance training (14). Figure 1: Plasma epinephrine (Epi) concentrations at rest and after 15 min of exercise at the same relative exercise intensity before and after 10 wk of endurance exercise training. Greiwe et al. J Appl Physiol 1999. Designation of a specific exercise intensity at which the adrenomedullary activity becomes significant is yet to occur, as catecholamines are always at work in the body. Unloaded cycling at approximately 10% VO2 max did not increase plasma catecholamines above resting values in young men (13). Likewise, as demonstrated in Figure 1, graded exercise on a bicycle ergometer did not increase plasma epinephrine above baseline at 54% VO2 max (8). However, Greiwe et al. demonstrated that norepinephrine and epinephrine (Figure 2) both increased with each 5% increment from 60% to 85% VO2 max before and after ten weeks of endurance training (14). Figure 1: Plasma epinephrine (Epi) concentrations at rest and after 15 min of exercise at the same relative exercise intensity before and after 10 wk of endurance exercise training. Greiwe et al. J Appl Physiol 1999. (PICTURE)

As such, it appears that the cutoff point for significant adrenomedullary stimulation during endurance exercise is in the 55-60% VO2 max range.

Exercise duration is also of appreciable significance in determining the adrenomedullary response to exercise. Galbo et al. found that although plasma epinephrine increased steadily with prolonged treadmill exercise to exhaustion at 76% VO2 max, graded exercise in the same subjects at 44, 77, and 100% of VO2 max yielded greater increases (9). Others have verified the trend of increasing plasma epinephrine with longer duration exercise (15,16). Clearly, there is an appreciable lag time between the onset of exercise and increases in plasma catecholamine concentrations. In bicycle ergometer exercise to exhaustion at 36, 55, 73, and 100% of maximal leg power (the equivalent of 115, 175, 230, and 318% VO2 max, respectively), significant immediate post-exercise increases in plasma epinephrine were only observed at 36 and 55% of maximal leg power. The mean duration of exercise at these two intensities were 3.31 and 0.781 minutes, respectively. At maximal leg power, mean duration was approximately six seconds, and the significant increase in epinephrine was not seen until 15 minutes post-exercise (17). Jezova et al. examined the differential responses of two bicycle ergometer tests of the same total work output but different duration and intensities. The researchers concluded that the overall catecholamine response is more dependent on exercise intensity than duration or total work output (18). Resistance training also has a profound impact on adrenomedullary activity. Bush et al noted significant increases in plasma epinephrine following two different resistance exercise protocols –one high force and the other high power – of the same total work. There was not, however, a significant difference in adrenomedullary activity between the two (19). In another study comparing body builders with powerlifters, Kraemer et al. found that a ten station resistance training session (comprising 30 total sets at 10 repetition maximum for various exercises) with short rest periods increased plasma epinephrine, norepinephrine, and dopamine significantly over pre-exercise values. No difference was noted between body builders and powerlifters on these measures (20). Pullinen et al. noted that although plasma epinephrine increased significantly with knee extensions to exhaustion at 20, 40, 60, and 80% of 1 repetition maximum (RM), the strongest stimulus to epinephrine, 20%, did not yield a significantly greater plasma epinephrine increase than the other three intensities (21). In contrast, Guezennec et al. observed that six sets of eight bench presses at 70% of 1RM yielded less of a plasma epinephrine and norepinephrine response than six sets of maximal repetitions at the same load (22). Therefore, intensity again appears to be paramount in determining the adrenomedullary response to exercise. Catecholamine Response to Recovery Several studies have noted abrupt drops in epinephrine values in the 5-15 minutes after the cessation of endurance, graded exercise, and resistance training sessions (8,17,19,23). In light of the aforementioned lag between the onset of exercise and increases in plasma catecholamine concentrations, one should note that epinephrine levels continue to increase for 15 minutes or more after very short duration, high-intensity exercise (e.g. sprints) (17,24). Additionally, 15 minutes following a 1000km ultra-marathon, free epinephrine concentrations remained well above pre-exercise values; clearly, the extensive nature of this duration appeared to be sufficient to elicit prolonged adrenomedullary activity (25). Chronic catecholamine adaptations to training have also been noted. Kjaer and Glabo found that endurance trained athletes demonstrated a greater ability than untrained subjects to secrete epinephrine in response to infusion of glucagon and acute hypercapnia and hypobaric hypoxia (26). This finding is significant, as Kjaer et al. had found previously (via epinephrine infusions in resting and cycling subjects) that plasma epinephrine concentration changes during exercise signify enhanced secretion rather than reduced clearance (27). In other words, endurance training appears to increase secretory capacity of the adrenal medulla. Lehmann et al. verified this phenomenon in finding that trained cyclists demonstrated lower plasma epinephrine concentrations than untrained subjects at the same relative oxygen uptake (28). The Opioid Peptides and Adrenomedullary Activity Since its discovery in the 1970s, the proenkephalin family of opioid peptides has become a recognized secretory product of the adrenomedullary chromaffin cells. Nonetheless, research regarding the opioid peptide response to exercise is limited (8,17,19). Perhaps the most studied member of the opioid peptide family is proenkephalin peptide F, which has responded to similar stimuli as epinephrine in previous studies (8,17,29).

Kraemer et al. noted differential peptide F responses during graded bicycle ergometer exercise in trained and untrained subjects. As Figure 2 demonstrates, in untrained subjects, peptide F increased similarly to epinephrine, whereas it peaked at 54% VO2 max and began to decline in trained subjects as exercise intensity increases to 83 and 100% VO2 max (8).

Figure 2: Plasma Epinephrine and Peptide F as a function of exercise intensity Kraemer et al. Proc Natl Acad Sci U S A. 1985 Note: squares indicate Trained group; triangles indicate untrained group. (PICTURE 2)

In a separate study, the differential responses between trained and untrained subjects were once again readily apparent when fit women had significantly higher plasma peptide F concentrations than their unfit counterparts at 80% VO2 max cycling (30).

Interpreting the peptide F response to varying exercise intensities proves to be challenging. Peptide F increased significantly during high intensity cycle exercise at 36% maximal leg power (roughly 115% VO2 max), but not at three greater intensities with shorter durations (17). Another study found that plasma peptide F increased significantly with graded exercise at 75 and 100% VO2 max (31). Conversely, recall that the aforementioned Kraemer study noted a drop-off point in plasma peptide F at 54% VO2 max in trained subjects (8). In support of this drop-off point, exercise at 80-85% VO2 max did not yield a significant increase in plasma peptide F (32). Likewise, when strength-trained men took part in separate high force and high power resistance training protocols, plasma peptide F was significantly decreased from baseline values at the end of the exercise sessions. Meanwhile, epinephrine increased dramatically as expected. The researchers hypothesized that epinephrine increases are made possible by decreases in enkephalin-containing polypeptides in the adrenal medulla (19). This theory is supported by research by Angelopoulos et al., who asserted that the opioid peptides have an inhibitory effect on the release of catecholamines during intense exercise (33). On a related note, in a study involving purposeful resistance exercise overtraining of trained subjects, peptide F concentrations were not significantly different between the overtrained and control groups. This similarity was present in spite of the protocol's previously demonstrated propensity to induce dramatic increases in epinephrine (29). The fact that chronic training increases adrenomedullary secretory capacity for epinephrine certainly supports this inverse relationship and helps to elucidate the question of why trained and untrained subjects have different peptide F responses during exercise. Opioid Peptides Response to Recovery Perhaps the most intriguing aspect of the opioid peptides as they relate to exercise is the recovery period response. Increases in plasma peptide F have been noted not only in the first 5-15 minutes of the post-exercise period (9,17,19), but also at 240 minutes after resistance training sessions, when the mean concentration was more than 80% above the mean pre-exercise value (19). Researchers hypothesize that this post-exercise proenkephalin surge is indicative of the opioid peptides' crucial role in recovery (9,17,19,29,34). Additionally, enkephalin-containing polypeptides appear to play an essential role in the immune response through mechanisms such as neutrophil activation, natural killer cell modulation, and coagulation facilitation (29, 35). Given the negative impact of the catecholamines on overall immunity, the opioid peptides may serve as a means for the adrenal medulla to counteract immunosuppression during and after exercise (29). Conclusions The adrenal medulla is stimulated to secrete catecholamines by a variety of exercise intensities, durations, and modes, with a minimum intensity of 55-60% VO2 max likely being the most requisite factor. Generally speaking, as exercise intensity and duration increase, so does catecholamine secretion (most notably epinephrine) by the adrenal medulla. In untrained subjects, increases in plasma proenkephalin-containing peptides parallel increases in catecholamines. At the cessation of exercise, free catecholamine concentrations in the plasma decline sharply. Simultaneously, in trained subjects, concentrations of opioid peptides, which were relatively unaffected by exercise above 54% VO2 max, increase to values well above baseline. As the potentially immunosuppressive catecholamines (which are secreted at higher rates in trained individuals) dissipate, the enkephalin-containing peptides can begin to enhance recovery from exercise while enhancing the immune response. In spite of this theoretical paradigm, more research is clearly warranted in order to fully understand the causes of the differential opioid peptide response to exercise in trained and untrained subjects. Furthermore, the exact interaction scheme of the opioid peptides and the catecholamines remains to be definitively agreed upon.

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