Fitness Fairytale - Lactic Acid

The DOMS Fairy.  He's as happy as he makes you....

Anyone who has participated in resistance training or some form of semi-vigorous exercise has surely experienced a visit from the DOMS Fairy at one time or another.  DOMS stands for Delayed Onset Muscle Soreness, a condition which peaks between 24 and 48 hours following a bout of exercise (Connolly, Sayers, and McHugh, 2003; Smith, 1992).  It can be generally characterized as a feeling of combined soreness and stiffness within the muscles directly targeted during a recent training session. You know what I’m talking about. That phenomenon that has you glued to the toilet seat a day or two after an intense lower body training session. 

Help! I've sat down and I can't get up!

Not only is DOMS a pain to deal with (pun intended) both in the figurative and literal sense, but it also has the capacity to be a decrement to athletic performance (Connolly et al., 2003; Wilmore, Costill and Kenney, 2008) and training productivity. While the concept of DOMS is not foreign to those familiar to the training game, nor to the vast majority of the lay public, the causation of the condition represents an entirely different story.

Ask anyone in the gym or on the practice field to ID the culprit behind their muscle soreness, and you’re likely to hear a reference to lactic acid mentioned somewhere in the answer.  Lactic acid has been getting a bad rap on this front for as long as I can remember now, but undeservedly so.  The confusion may come from the production of lactic acid during activities which rely heavily on the fast glycolytic system for energy (Adenosine Triphosphate or ATP) production.  Fast glycolysis is the primary energy producer for training modalities such as weight training, plyometrics, sprinting and agility drills (short duration / high intensity endeavors).  Not surprisingly, these are the same types of activities that tend to induce the most prominent bouts with DOMS. 

Glycolysis refers to the breakdown  of carbohydrate for energy (ATP) production within the body; two primary systems exist, fast (energy production required at a high rate, insufficient oxygen, pyruvate converted to lactic acid) and slow (energy production required at a slower rate, sufficient oxygen, pyruvate utilized within the oxidative system). 

It’s also worth mentioning that for a time, a theory did exist linking lactic acid to the occurrence of DOMS.  However, more recent research has largely minimized the likelihood of this theory, showing that blood lactate concentrations (for simplicity’s sake think of this as lactic acid) typically return to pre-exercise levels within an hour of training (Baechle and Earle, 2008).  Additionally, researchers have also documented instances where exercises promoting high levels of blood lactate produced minimal DOMS, while others promoting low levels of blood lactate incited the occurrence of the condition (Dierking and Bemben, 1998; Wilmore et al., 2008).  Now that we’ve nailed down the origin of the confusion, provided you with a crash course in bioenergetics and cleared lactic acid’s good name, let’s look at the real story with DOMS.

Cool picture to break up the science monotony

To begin, it may prove helpful to think of DOMS as exercise-induced muscle damage.  This damage is caused particularly by way of unfamiliar exercises or those requiring the use of eccentric muscular contraction (contraction of a muscle while it lengthens).  Weight training, sprinting, plyometrics and agility work all require the use of eccentric muscular contraction to a relatively high degree as compared to the likes of distance running.  Hence the high incidence of DOMS associated with these activities.  Structural Damage to the muscle prompts the arrival of all the same culprits one would expect in any instance of bodily injury; namely swelling and inflammation. While not completely understood, it is believed that the inflammation process, prompted by the structural damage,   promotes the synthesis of various chemical substances which in turn cause pain via the stimulation of afferent nerve endings (Connolly et al., 2003). 

Unfortunately there remains no real means for the complete avoidance of DOMS.  Its severity may be attenuated by avoiding unfamiliar exercise, limiting eccentric contractions or by utilizing a warm-up as a means of decreasing viscosity within a given muscle group before training (Szymanski, 2001), but that just about does it.  In the end, DOMS is something that is simply a part of the training game for the foreseeable future.  My best advice, learn to love the good hurt.

References:

Baechle, T. R. and Earle, R. W. (2008).  Essentials of Strength and Conditioning. Champaign IL: Human Kinetics.

Connolly, D. A. J., Sayers, S. P., and McHugh, M. P. (2003).  Treatment and prevention of delayed onset muscle soreness. Journal of Strength and Conditioning Research, 17(1), 197-208.

Dierking, J. K. and Bemben, M. G. (1998).  Delayed onset muscle soreness.  Strength and Conditioning, 20(4), 44-48.

Smith, L. L. (1992). Causes of delayed onset muscle soreness and the impact of athletic performance: a review.  Journal of Applied Sports Science Research, 6(3), 135-141.

Szymanski, D. J. (2001).  Recommendations for the avoidance of delayed-onset muscle soreness.  Strength and Conditioning Journal, 23(4), 7-13.

Willmore, J. H., Costill, D. L. and Kenney W. L. (2008).  Physiology of Sport and Exercise.  Champaign IL: Human Kinetics.