You’ve just completed your hill repeats. The workout went great, confidence is at an all time high, and you can’t wait to crush the next one. However… the next day you wake up and you’re stiff as a board. Your quads ache, your calves scream; you’re wondering what you did to deserve this torment. Exercise induced muscle damage and its corollary Delayed Onset Muscle Soreness (DOMS) often results from novel, intense exercise, and typically lasts 24-48 hours after the exercise, and subsides within 96 hours. DOMS itself is a mechanical disruption to the sarcomeres (the fundamental units of muscle cell contraction) that results in localized inflammation, swelling, and free radical proliferation of the muscle fiber(1). This lingering soreness and transient decrease in strength with DOMS has huge impacts for athletes of all abilities - you can’t practice or perform to your full potential if you’re sore! Traditional treatments (stretching, massage, ice, compression, etc.) have long been staples for DOMS amelioration with positive yet limited results; however one relatively new approach - tart cherry juice - is emerging as a promising alternative.
A large aspect of the soreness we experience with DOMS is related to the inflammation, swelling, and free radical proliferation mentioned earlier. Tart cherries have been identified as a foodsource high in antioxidant and anti-inflammatory compounds, which has led researchers to speculate on their ability to alleviate inflammatory conditions.(2) Considering these potentially beneficial effects, researchers assembled a randomized controlled trial measuring pain, muscle tenderness, muscle strength, and relaxed elbow angle before and after a maximal bout of bicep curls.
For the study, one group of subjects received 12oz bottles of tart cherry juice, the other group received a control drink (made to look and taste just like tart cherry juice) and were instructed to drink one in the morning, one in the evening, for the next 8 days. On day 4, subjects returned to the lab and performed their maximal bicep curl exercise session, which resulted in significant DOMS related soreness. Each of the following 4 days, the subjects returned to the lab and again measured pain, muscle tenderness, muscle strength, and relaxed elbow angle, and the data was gathered.
The study found that for the control trial, strength loss was 30% at 24 hours and still 12% at 96 hours. In contrast, the cherry group strength loss was only 12% at 24 hours, and actually 6% above baseline measurements at 96 hours. Similarly, pain measurements in the control group increased until a peak at 48 hours, whereas the cherry group pain intensity peaked in only 24 hours. Measurements that did not show a significant difference between the groups included the resting elbow flexion angle and muscle tenderness.
So what does all this mean? Although from this study it is not possible to definitively conclude that tart cherry juice supplementation prevented muscular damage/DOMS, it does seem to indicate a protective effect of the cherry juice and a preservation of muscle function. Less strength loss and decreased pain related to DOMS means you’ll be more fully recovered and ready to tackle that next workout at a higher quality level.
I remember my dad asking me, driving on our way to high-school cross-country practice, why we had so many “easy” days. Why were only a few training days of the week spent really pushing ourselves, while the remainder of the week spent seemingly putzing around at a conversational jog. It was never something I’d really considered. We both grew up playing ball-sports, where it seemed every practice had the potential of sending you over to the sidelines gasping for air or heaving in the nearest trash-can. Running, however, was different, as it involved a delicate balance of training intensity, duration, and frequency. So - one must ask, is the distribution of hard days and light days really a self-organized optimum for endurance athletes, or a product of tradition and/or superstition?1 And, why can’t we train hard all the time?
Stephen Seiler’s review(1) looking at training intensity and duration distribution in endurance athletes helps us tie what research is available to the mechanisms that might be at play. His paper demonstrated that the training characteristics of nationally or internationally competitive endurance athletes seem to converge on a typical intensity distribution in which 80% of the training sessions are performed at low-intensity (~ less than 80% VO2max), whereas 20% were spent at high-intensity (~ greater than 80% VO2max).
From a macroscopic view, we can use Banister’s(2) (sorry, not Roger Bannister) “Fitness-Fatigue” model to see why this might be the case. Training (intensity, duration) and recovery (rest interval, nutrition) variables interact to induce both fitness (i.e. positive physiological adaptations), and fatigue (i.e. stress response and associated negative health outcomes) affects. The fitness after-effect presents as dull in magnitude, but long in duration, and manifests as a long-term improvement in performance, while the fatigue after-effect is initially large in magnitude with a brief duration. The model may be best illustrated by the figure below, showing that as the duration of the fitness after-effect is longer than the fatigue after-effect, a period of recovery allows the fatigue to diminish while fitness remains high. Conversely, stressful periods of training without sufficient recovery results in an accumulation of fatigue and an increase in the systemic or main fatigue after-effect.
If you have ever trained for an endurance event, you don’t need a theoretical model to tell you that 7 days of high-intensity workouts in a row isn’t a good idea. This is because our bodies need time to recovery so that we can maximize the benefits from our most recent hard session. Think of endurance training, light days and hard days, simply as a stimulus for adaptation.
More microscopically, the magical 80-20 intensity distribution strategy may be ideal for optimization of cellular adaptive signals and stress responses within the body. Positive adaptations with endurance training include higher mitochondrial density, higher capillary density, greater enzyme density/function, and more, which help improve VO2 among other markers and functionally improve performance(3). Cellular signaling studies are continuing to emerge, but some key takeaways might include that: 1) exercise duration and intensity can drive gene expression for positive adaptations, and 2) ceiling effects for signal amplitude are seen rapidly with repeated high-intensity interval exercise, whereas increased frequency at low-intensity may provide greater scope for expansion of the total signal for gene expression (greater overall effect)(1).
It has also been found that recovery within the autonomic nervous system (measured via heart rate variability) is very rapid after training bouts of 60% VO2max (low intensity), but becomes markedly delayed when exercise increases to a threshold or higher intensity4. Heart rate variability is a non-invasive, practical, and reproducible measure of autonomic nervous system function5, and is gaining traction in the training and medical community as a valuable marker for objective individual recovery. Fluck et al6 sums it up well: “Changes in physiological capacity over time are hypothesized to be the net result of transient increases in gene expression during recovery from repeated bouts of exercise.”
So - the body needs “lighter” recovery days to maximize the positive fitness effects that occur with our “heavier” training. This balancing act of exercise intensity, duration, frequency, and internal individual factors (life stress, work stress, nutrition, sleep habits, etc), is what makes coaching such an art. Like most things, the traditional model of 80-20 intensity distribution is something coaches have known forever, it’s just now that research is starting to catch up.
Some original content.