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In Defense of Distance: Part II

One concept we briefly addressed in In Defense of Distance but did not elaborate upon was how distance training may improve recovery.  I say “may” because the formal literature provides no clear cut answers.  In coaching we have our suspicions via anecdotal observation, but it is difficult to parse the cause and effect: does additional training improve recovery, or are fitter athletes simply less taxed than others?  Even if they may appear to recover faster, maybe they’re just fitter and not working as hard as others?  These aren’t easy questions to resolve, but we can make a few inferences.

It can be challenging to defend high volume programming to outsiders who can’t fathom how ten mile runs, 5,000 yard swims, and three hour bikes can promote recovery.  Indeed, given the vast literature (and personal observation) showing a correlation between added volume and musculoskeletal injuries, the simple (but not always correct) answer is to just train less.  However, we also know that most successful athletes put in in plenty of volume.  The concept of individuality is crucial here as too much volume for one person should not indict an entire training approach. 

As for recovery…Literature is consistent that aerobic training helps the restore body to a parasympathetic state.  There’s a reason we say “recovery workout,” and why low intensity, long distance training may in fact be restorative, contrary to popular intuition.   When people get into trouble is when the low intensity is not so “low”, whether by racing recovery sets or by training in a group too advanced hoping they get dragged along to better performances.   

Raczak (2006) studied a group of regional class runners and explored the role of aerobic training in autonomic nervous system regulation.  This study was interesting because it also indirectly explored the effects of periodization.  Authors noted, “Moderate-intensity endurance training causes increased parasympathetic activity while very intensive (extreme) exercise loads may lead to persistently elevated sympathetic tone in champion class athletes preparing for competitions.”   

Subjects began with a several week base, or preparatory period.  During this period, authors noted a shift away from sympathetic dominance toward parasympathetic dominance marked by increased heart rate variability (HRV) and baroreceptor sensitivity, which is a measure of the arteries’ responsiveness (higher is better).  “Long-term intensive exercise training, employed by regional class runners preparing for competitions, changes the autonomic profile, promoting parasympathetic dominance”

A “starting period” followed the preparatory period.  VO2 max increased, in the “starting period” during which more intense training was introduced, suggesting that the base period followed by intensive training was successful in promoting fitness gains.  This may seem like a given with the addition of increased intensity, but not so.  Uusitalo (2000) studied overtrained athletes who increased their volume of high intensity training by 125 %( high intensity was defined as 70 - 90 % of maximal oxygen uptake (V˙O2max)).  These athletes actually reported a decrease in VO2max, whereas the control group showed no loss. 

Further evidence that increases in aerobic training may lead to a parasympathetic shift… Tian (2006) divided forty-one healthy young men into aerobic and anaerobic endurance training groups for an eight week study.  Authors found, “The autonomic balance in aerobic endurance group had an increasing parasympathetic activity and relatively decreasing sympathetic activity. This group showed a parasympathetic predominance and increase of HRV.  While in the anaerobic group there was a relative stabilization with the function of autonomic nervous system.”  (note again: higher HRV is good)  This study obviously has some limitations as only eight weeks with non-athletes, but it does show the trend toward parasympathetic response via aerobic training.   

Nonetheless, these results have been shown consistent over a longer term.  Levy (1998) studied both old and young males over six months.  Both groups performed aerobic training during this period.  Authors noted increased maximum oxygen consumption by 21% in the older group and 17% in the young group (we wouldn’t expect nearly the same magnitude in highly trained subjects).  Most importantly for this discussion, training decreased resting heart rate in both the older (-9 beats/min) and the young groups (-5 beats/min).   HRV also increased at rest.  Conclusion: “Exercise training increases parasympathetic tone at rest in both the healthy older and young men.” 

Although not directly related to the autonomic nervous system, aerobic training has also been shown to improve recovery during repeated sprint efforts.  This quality is critical for team sports, but also for individual sports (Track, swimming, cycling) in which interval training is part of the regime.  One theory is that a stronger aerobic base will improve recovery between repeats.  Two athletes can hit the same times, but one might be less taxed from the workout because he/she recovers better.  This concept is often discussed in theoretical terms, but there is actually some scientific basis for it.

Bucheidt (2011) studied 18 moderately trained males and measured maximal aerobic speed, 10k time, and shuttle run performance (how much distance covered during 2 x 15 second sprints with 15 seconds recovery).  Authors also measured reoxygenation rate after the sprints.  Subjects performed eight weeks endurance training after initial testing.   At the post test, all performance marks improved, including the shuttle run the reoxygenation rate after sprints.   Conclusion: “Present findings confirm the beneficial effect of endurance training on post-sprint muscle reoxygenation rate, which is likely to participate in the improvement of repeated-sprint ability after training. These data also confirm the importance of aerobic conditioning in sports, where repeating high-intensity/maximal efforts within a short time-period are required.”

Despite the importance of parasympathetic dominance for recovery, there comes a time to tighten the screws, so to speak.  The lesson here is to pick your battles wisely.  We WANT a sympathetic response when the gun goes off, but too much intense training too long leads to staleness and a loss of parasympathetic dominance at rest. 

Iellamo (2002) studied the Italian junior national team of rowing (n=7) before their world championship.  Athletes gradually increased training load (volume and intensity) up to 100% of maximum twenty days before worlds.   The early buildup resulted in a parasympathetic shift, but at 100% training load all relevant markers noted a shift toward sympathetic dominance. As a side note, three athletes later won medals in the World Championship. (“This study indicates that very intensive endurance training shifted the cardiovascular autonomic modulation from a parasympathetic toward a sympathetic predominance. This finding should be interpreted within the context of the substantial role played by the sympathetic nervous system in increasing cardiovascular performance at peak training.”)

Conclusion

Easy aerobic training is one of many tools we can exploit to modulate the autonomic nervous system for the desired responses.  We all know the textbook benefits of increased capillarization and mitochondrial density via aerobic volume, but autonomic regulation is one overlooked benefit.  If people break down on mileage, it’s usually not the mileage; it’s often something else, whether not going truly “easy,” unresolved movement/technical issues, or factors outside training that impair recovery ability. 

References

Raczak G, Daniłowicz-Szymanowicz L, Kobuszewska-Chwirot M, Ratkowski W, Figura-Chmielewska M, Szwoch M.  Long-term exercise training improves autonomic nervous system profile in professional runners.  Kardiol Pol. 2006 Feb;64(2):135-40; discussion 141-2.

Iellamo F, Legramante JM, Pigozzi F, Spataro A, Norbiato G, Lucini D, Pagani M.  Conversion from vagal to sympathetic predominance with strenuous training in high-performance world class athletes.  Circulation. 2002 Jun 11;105(23):2719-24.

Tian K, Qin J, Huang L, Long M, Wu J, Yu S, Yu Y.  [The effect of aerobic and anaerobic endurance training on the regulating function of autonomic nervous system and its significance].  Sheng Wu Yi Xue Gong Cheng Xue Za Zhi. 2006 Oct;23(5):1020-3.

Buchheit M, Ufland P.  Effect of endurance training on performance and muscle reoxygenation rate during repeated-sprint running.  Eur J Appl Physiol. 2011 Feb;111(2):293-301. Epub 2010 Sep 25.

Levy WC, Cerqueira MD, Harp GDJohannessen KA, Abrass IB, Schwartz RS, Stratton JR.  Effect of endurance exercise training on heart rate variability at rest in healthy young and oldermen. Am J Cardiol. 1998 Nov 15;82(10):1236-41.

Uusitalo AL, Uusitalo AJRusko HK.  Heart rate and blood pressure variability during heavy training and overtraining in the femaleathleteInt J Sports Med. 2000 Jan;21(1):45-53.

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