The time of day that you train can make a difference in performance. In this article, we will explore the differences in time of day for training along with the possibilities for honing in on the optimal training time for your athletes to gain the best adaptation. Testing of hormones in the saliva (such as cortisol and testosterone) can be a reliable way for determining if your athlete is responding appropriately to the training or is in a state of overtraining. For most of the coaches out there working with age group athletes, the ultimate control over the timing of training sessions is determined by work schedules, training center hours, master’s swim practice times, and school pick-up and drop-off times. On the other hand, coaches of elite athletes may have complete control over these variables. Whichever it may be, we can learn from some of the research from the past few years regarding diurnal variation in the types and amounts of anabolic and catabolic hormones released throughout the day.
Laboratory testing is quickly becoming completely attainable for most coaches and athletes without the need for a physicians’ order. The advantage of this for athletes, particularly those who are remotely coached, is that relatively inexpensive tests can reliably determine optimal training time. Further, if the data points are far outside of normal, this can be an opportunity for coaches to refer to physicians for insight into overtraining. This is in large part a bonus and not a necessity for athletes. Incidentally, a smartphone-compatible device for testing cortisol is expected to be made available later this year. Another in a preliminary launch phase from the San Diego-based company Cue will test five of the most commonly analyzed blood markers, including testosterone. The latter will certainly become useful for athletes and coaches seeking to maximize performance adaptations by looking at key training sessions. For those really looking to go deep into their analysis, this will theoretically go quite far in making detail affordable in the long-term.
Examining the details of cortisol and testosterone, the optimal strategy is to examine the ratio between the two values. The values may be measured by salivary tests as these levels are highly correlated with serum measurements (VanBruggen, 2011). Resting values and, in the case of endurance athletes, values during the recovery period after a key training session, are best for examining the short-term training status of an athlete (Fry, 2000). According to the research, an increase in the ratio of testosterone to cortisol in the recovery phase after intense training blocks is highly correlated with increases in performance. In fact, the more training experience an athlete has, the greater the correlation and increase in performance with increase in testosterone to cortisol ratio. Citing research in weightlifters, an increase in the ratio of greater than 30% was correlated with increases in performance (Fry, 1994). The opposite is true, however, with decreases in performance occurring when the ratio decreases. The practical application of this research is to test an athlete’s testosterone to cortisol ratio within about 15 minutes of the conclusion of a key training session to ensure that the athlete is experiencing optimal adaption potential (>30% increase in ratio) and not overtraining (less than a 30% increase).
Specific to cyclists, back in October of last year, researchers in Brazil published a study in which they analyzed key anabolic and catabolic hormones related to exercise (cortisol, insulin, total and free testosterone) in nine male cyclists. The researchers sought to determine when the cyclists would perform optimally in terms of pacing in a 1000-m time trial. Specifically, the 1000-m time trial was selected because it is supported both by the aerobic and the anaerobic energy systems and could therefore be utilized as a tool to analyze both. The subjects came to the lab four times: once for an incremental test, once for an acclimation trial, once to perform the time trial at 6am and the other to perform the test at 6pm. They found that there was a significantly better performance for the athletes at 6pm rather than 6am. This suggests that not only is performance increased in the evening, but that the reason is that there is a normal hormonal milieu that is enhanced during the late afternoon into evening hours.
Cortisol has also been studied as it relates to immune system function in trained swimmers. British researchers looked into cortisol and IgA (an immune system marker) values at different times throughout the day, both before and after morning and evening practice sessions. They found that stress response was highest and immune system response was lowest in the morning and the opposite was found in the evening. From this, the suggestion is to program for higher-intensity work in the afternoon practice and even to avoid early-morning practices whenever possible to gain the greatest results with the lowest chance of depressed immune function (Dimitriou, 2002).
These data truly confirm what researchers and coaches have known for a long time. However, we can still use this information to appropriately program for our athletes. Once salivary tests for cortisol are performed and it is ruled out that there is any abnormal adrenal function (coach translation: overtraining is occurring), it is optimal to program training sessions for specific times during the day. Normal cortisol fluctuations are seen in Figure 1 (Brown, 2001). Normal testosterone levels (in men) are displayed in Figure 2 (Plymate, 1989).
Figure 1: Daily Cortisol Patterns. Here, what is important to highlight here is in graphs A and C where spikes in cortisol can be seen in the morning hours. Lowest levels of cortisol occur in the late afternoon and early evening hours. When matched with the testosterone values in Figure 2, a pattern can emerge that reveals a generalized optimal training time.
Figure 2: Daily Testosterone Patterns (males). Values for normal healthy men are displayed with closed circles and values for elderly men are displayed with open circles. In this graph, the important detail is the rise in values that occur after the decline in cortisol values. This peaks at around 4pm in the elderly males and around 5pm in the young males. Both values rise again overnight, enhancing the potential for recovery during sleep.
It should be noted that the above applies most directly to male athletes as there are significant variations in females due to monthly cycles. This concept is outlined with more detail in an article by E. A. S. Al-Dujaill written in 2012. Selected graphs from the article are displayed as Figure 3. A basic interpretation of these suggest that optimal training timing for younger females may be later than same-age males (around 7pm for 18-29yo females), but that those values may subsequently shift to slightly earlier times in older females (around 5pm for 30-39yo females), though all age groups appear to have a slight increase at around 7pm. Granted, far more has been written about the application for males than for females. As enhanced ability for monitoring of biomarkers through inexpensive devices becomes more common, we will certainly see this applied to all ranges of athletes.
Figure 3: Testosterone values for healthy females (age range is indicated for each). (A) indicates pre-menopausal women, while (B) indicates post-menopausal women.
There are practical methods for this based upon the focus of the training phase. First, place all easy, aerobic activity early in the morning. The stress response to prolonged endurance activity is pronounced, causing an increase in cortisol values. Because of this, the best time to put these bouts is in the morning when both cortisol and testosterone are at their peak. So long as there is adequate recovery during the day, the cortisol will be removed and not cause a determent in performance for the afternoon session (this is a hint to our hard-charging athletes who work an intense day-job, which also increases cortisol). Though it is beyond the scope of this article, the timing of high-glycemic index foods will be critical in this 2-hour post-exercise window to enhance the clearance of cortisol by the release of insulin.
Next, place all of the key sessions in the evening as much as possible. Take a look at the daily pattern graphs of both cortisol and testosterone. Under normal circumstances, the values will result in the highest testosterone to cortisol ratio at around 5pm, when testosterone undergoes a second peak. This is also the optimal time to perform strength training and speed work. Fortunately, TrainingPeaks has a workout session timing feature that allows for precise timing of these training sessions.
If and when you and your athlete are looking for the optimal training time for key sessions, you can move forward with the salivary analyses currently offered online through sources such as directlabs.com and zrtlab.com. Prices range from about $50 to nearly $300, depending upon how detailed you are with each of the analyses. Practically, this would be for the athlete seeking precise timing of key training sessions, seeking the highest possible testosterone to cortisol ratio. If the predictions ring true, salivary testing of these hormones will actually be a practical and inexpensive method of monitoring training readiness, response, and for the prevention of overtraining.
Jasymin Evans also contributed to this article.