Two-A-Day Training - That's Bogus, Right? No - Increased Fat Oxidation in Endurance, 2.4x Higher Max. Volume, 2.6x Higher Time to Exhaustion in Resistance Training Study

Two-A-Day Training - That's Bogus, Right? No - Increased Fat Oxidation in Endurance, 2.4x Higher Max. Volume, 2.6x Higher Time to Exhaustion in Resistance Training Study

AM/PM build muscle citric acid synthase endurance fat oxidation intensity techniques performance RER training training frequency two-a-days workout routines

If you feel totally wasted after every workout, I have bad news for you. In the two-a-day studies at hand the rest between the first and second workout was only 2h! Not exactly much time to recover, but the idea is to "train low" (on glycogen) on the second workout.

It sounds like madness or something for the "enhanced" athletes, but an older scientific study I recently dug out, accidentally, says that "training twice every second day may be superior to daily training" (Hansen. 2005). When I tried to learn more about this topic, though, I had to realize that the evidence is scarce. Similar results have been presented by Yeo et al (2008), though, albeit for trained triathletes and cycling.

In their study, Yeo and colleagues determined the effects of a cycle training program in which selected sessions were performed with low muscle glycogen content on training capacity and subsequent endurance performance, whole body substrate oxidation during submaximal exercise, and several mitochondrial enzymes and signaling proteins with putative roles in promoting training adaptation.

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Now, the interesting thing about Yeo's study and the reason I want to discuss their results first is that the scientists from the School of Medical Sciences at the RMIT University in Victoria, Australia used trained subjects - seven endurance-trained cyclists/triathletes who were used to training daily anyway. During the three week study period, however, the subjects had to stick to one of the following training schedules:

• Daily training (Daily - aka "High") - In this group the subjects alternated between 100-min steady-state aerobic rides (AT) one day, followed by a high-intensity interval training session (HIT; 8x5 min at maximum self-selected effort) the next day.
• Twice every second day training (Two-A-Day - aka "Low") - Subject who had been randomly assigned to this group performed the AT, first, then 1–2 h later, the HIT. 

Forty-eight hours before and after the first and last training sessions, all subjects completed a 60-min steady-state ride (60SS) followed by a 60-min performance trial. Muscle biopsies were taken before and after 60SS, and rates of substrate oxidation were determined throughout this ride and the results were... well, let's say interesting:

Figure 1: Markers of fact glycogen use and fat oxidation during steady state exercise after 3 weeks of training (Yeo. 2008)

As you can see markers of mytochondrial beta oxidation (citrate synthase), as well as the glycogen concentrations and whole body fat oxidation during the 60 minute steady state ride pre-/post-test increased exclusively in the "two-a-day" group. That's a relevant results, even though the increase in cycling performance improved by 10% in both Low and High and the performance during the HIIT trials, which were performed after the aerobic rides, suffered in the LOW, i.e. the "Two-a-Day" arm o the study (see Figure 2, right).

Figure 2: During the training sessions the HIIT performance is initally lower, but even then the increased capacity to oxidize fat and thus ability to spare gluocose pays off in slowly increasing performance markers (no sign. difference anymore) after only 7 HIIT sprints - during a race the fat oxidation boost (right) may be even more important (Yeo. 2008)

Why's that beneficial? Well, while it is not relevant for short bouts of HIIT, the significant increase in fat oxidation during the exercise test (see Figure 2, right) indicates that, the subjects' ability to use fuel as substrate during steady state, as well as longer interval rides increased significantly. The spared glycogen may then, during a longer race, for example, decide victory and defeat when the glycogen depleted every-day trainer cannot keep up with the glycogen sparing two-a-day every other day trainer during a sprint at the end of a race.

Want to learn more? At this point you may be reminded of a previous article of mine with the telling title "8x Increase in "Mitochondria Building" Protein PGC1-Alpha W/ Medium Intensity Exercise in Glycogen Depleted Elite(!) Cyclists: Training Revolution or Recipe for Disaster?". If not, I suggest you head back and read it now!

The obvious question that's probably preying on your minds already is: How on earth does that relate to strength training, bro? Well, let's see... so, in the strength training study by Hansen, et al., the authors actually speculated to observe an effect as it was observed in the study I discuss in the article I referenced in the red box, i.e.  that "training at a low muscle glycogen content [during a second workout on the same day] would enhance training adaptation" (Hansen. 2005). Therefore, the Hansen et al performed a study in which seven healthy untrained men performed knee extensor exercises with one leg trained in a two-a-day fashion (2h rest between the 1h sessions), the other one in everyday. Luckily, the study duration in this study was 10 and not just 3 weeks.

Against that background it is not surprising that the training load increased significantly. Since the latter has little to do with the mitochondria, it is also not that surprising that the increase in maximal workload was identical for the two legs. What may be surprising for those who think that training twice a day would be bogus, however, is that the time until exhaustion and total volume during the post-test was "markedly more increased" in the leg that was trained twice a day, albeit only every other day vs. the one that was trained daily, but only once (see Figure 3).

Figure 3: Relative performance increases from pre- to post-test (left) and glycogen levels before and after exhausting bouts of knee extensor exercises (right) | high = daily training, low = twice a day, but only every other day (Hansen. 2005).

Just like in the previously cited cylcling study by Yea et al, the effect may be attributed to (a) increased resting muscle glycogen and (b) higher activities of the mitochondrial enzyme 3-hydroxyacyl-CoA dehydrogenase and citrate synthase which are both involved in the oxidation of fat in the mitochondria of your muscle.

"Just One More Set" (1/2): Metabolic Response to 10,000kg vs. 20,000kg Regimen. EPOC: Do Reps and Loads Both Figure? And What About Elite Athletes Do They Need More? Find answers to these questions, here!

Bottom line: While it should be obvious that (a) further research is necessary and (b) the benefits of two-a-day training will depend on your training goals, the (older) studies presented in this article clearly support what Hansen et al phrase like this: "training twice every second day may be superior to daily training" (Hansen. 2005).

Ok, while the benefits for cyclists are obvious, it will have to be proven that the additional one or two reps or the extra high intensity set you may be able to do due to the improvements in glycogen sparing fatty oxidation will actually increase your muscle gains, but the mere possibility that training twice a day every other day could be better than training everyday, which is something I see people do at the gym regularly, is intriguing, isn't it? Comment!

References:

• Hansen, Anne K., et al. "Skeletal muscle adaptation: training twice every second day vs. training once daily." Journal of Applied Physiology 98.1 (2005): 93-99.
• Yeo, Wee Kian, et al. "Skeletal muscle adaptation and performance responses to once a day versus twice every second day endurance training regimens." Journal of Applied Physiology 105.5 (2008): 1462-1470.

Nine Short Workouts (AM+PM) p. Week Yield Extra Strength, Size and Performance Gains Compared to Volume Matched 3-Day Split, All Differences are Non-Significant, Though

Nine Short Workouts (AM+PM) p. Week Yield Extra Strength, Size and Performance Gains Compared to Volume Matched 3-Day Split, All Differences are Non-Significant, Though

AM/PM bodybuilding build muscle exercise science fitness fitness model frequency high volume lose fat performance training science training volume workout frequency workout routines

15 min in the AM, 15 in the PM = Win? For many of you that may sound laughable, but according to a recent study from the University of Copenhagen it is at least as effective as three "mammoth" workouts-sessions per week.

What kind of trainee are you? Do you hit the gym thrice a week, spend two hours there and crawl out of the gymdoors totally exhausted? Yeah... Well that means you're not the fitness model guy, who trains twice a day for 15-20 minutes only and swears that this is the only way to do it?

After all these questions you're probably asking yourself if the answers you gave in your mind were good or bad for ya? Right? Well, eventually, both forms of training can be equally effective. If we take a closer look at the non-significant study outcomes in a recent paper by scientists from the University of Copenhagen (Kilen. 2015), though body composition and strength may in fact benefit more if you train more frequently - even if the total workout volume is the same.

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Workout volume? Yes, that's the number of sets and reps. So, let's say you do three 45-minute training sessions weekly, including 1 strength on Monday, 1 high intensity cardiovascular (HIIT) session on Wednesday, and 1 muscle endurance session on Thursday, then those 3x45 minutes + warm-up exercise are your total workout volume.

In case that's what you're doing on a regular basis, you're training just like those of the 21 study subjects (10 men, 11 women; 25 +/- 3 years) with some previous training experience who were randomly assigned to the "classical" training program in the previously mentioned study by Kilen, et al. (2015). If you're rather the fitness model type, you may recognize your own training in what the other subjects did, i.e. a "micro training" program with a total of nine 15-minute training sessions weekly that were divided equally between strength training, high-intensity cardiovascular training, and muscle endurance training and performed in the AM and PM from Monday to Friday (there was no PM training on Friday, though, and cardio and strength were rotated | see caption of Table 1).

Table 1: Description of the two different training regimen (Kilen. 2015) | *To minimize the potential negative effect of concurrent cardio + strength training, MI performed 2 days of strength (Mon and + Tue) and 1 day of cardio training (Wed) in odd weeks, and 1 day of strength (Mon) and 2 days of cardio training (Tue + Wed) in even weeks.

Unlike the training frequency and rest between workouts, the strength training, HIIT and muscular endurance training sessions, themselves, were identical in both groups:

• Strength training consisted of leg exercises (deadlifts, lunges, step-ups, and 1 leg squats), with 1–2 warm-up sets and 2–3 target sets of 8RM, and upper-body exercises (pullups, dips, weighted push-ups, and 1 arm rows), with 1–2 warm-up sets and 2–3 target sets of 5RM. For progression, the exercises were adjusted using extra loading (sandbags in 1-kg steps) if the subjects were able to accomplish more repetitions than prescribed. If the subjects were not able to perform the number of repetitions prescribed, they performed as many as they could in proper form and finished the set conducting only the eccentric phase of the exercise. 
• High-intensity cardiovascular training (HIIT) consisted of running for 2 and 4 minutes at an average speed of 15.1 and 14.5 km/h, respectively, which elicited ;90% maximal heart rate during exercise. Micro training performed two 4-minute run intervals in the morning with 3 minutes of rest in between and four 2-minute run intervals in the afternoon with 1 minute of rest in between. Classical training performed three 4-minute and six 2-minute run intervals in the same training session with the same rest as MI in between. The training volume was evaluated and the only significant difference was running distance during 2-minute and 4-minute intervals, where MI ran significantly further than CL in each interval. 
• Muscle endurance training consisted of three 5-minute exercise sessions involving 5 different exercises performed continuously for 30 seconds with 30-second rest periods. Micro training conducted 3 sessions; the first was “easy,” the second “hard,” and the third “very hard.” Classical training conducted 9 sessions in the same order, starting over with “easy” on the fourth and seventh sessions. The exercises were weighted lunges (with a 20-kg sandbag); push-ups; shuttle runs; abdominal exercises ([a] regular sit-ups from a supine position with knees bent at 908, fists in contact with the ears and the lumbar arch supported by a folded towel, and [b] diagonal sit-ups from a horizontal supine position, outstretched hand to opposite raised foot, alternating); and back exercises ([a] back extensions on an incline bench and [b] kettlebell swings in a standing position). 

As Kilen et al. point out, "[a]ll training sessions were supervised by scientific staff, and subject attendance" as well as "[h]eart rate [...] during high-intensity cardiovascular training and muscle endurance training for the last 5 weeks of the training intervention" (Kilen. 2015) were recorded.

Figure 1: Relative pre- vs. post changes in all measures performance markers (calculated based on Kilen. 2015).

After the 8-weeks on the respective training regiment, a comparison of the pre- vs. post-training data yielded the following results:

• Increases in shuttle run performance were observed in both group, albeit with a higher significance as far as the pre- vs. post-difference is concerned in the classical training (CL) vs. micro training (MI) group (MI: 1,373 +/- 133 m vs. 1,498 +/- 126 m, p < 0.05; CL: 1,074 6 213 m vs. 1,451 6 202 m, p , 0.001).
• Significant improvements in peak oxygen uptake (3,744 6 +/- 615 mL/min vs. 3,963 +/- 753 mL/min | p < 0.05), maximal voluntary isometric (MVC) force of the knee extensors (646 +/- 135 N vs. 659 +/- 209 N | p < 0.001), MVC of the finger flexors (408 +/- 109 N vs. 441 +/- 131 N, p < 0.05), and the maximal number of lunges performed in 2 minutes (65 +/- 3 vs. 73 +/- 2, p , 0.001), however, were seen only in the micro = high frequency training group.

The question you may be asking yourselves now is: Why does the headline say that there were no significant differences? Well, the lack of statistical significance of the improvements in the classical training group does not suffice for a statistically significant between difference to the micro training group. Statistical significant inter-group differences did not exist either before or after the study. The scientists conclusion that

"similar training adaptations can be obtained with short, frequent exercise sessions or longer, less frequent sessions where the total volume of weekly training performed is the same" (Kilen. 2015)

is thus absolutely correct. The fact that statistical significance for the aforementioned study outcomes was achieved in the micro, yet not in the classical training group does still suggest that the high(er) frequency training regimen may have an adaptive edge... albeit in terms of study outcomes not everyone will deem practically relevant.

Figure 2: Neither the in-group nor the inter-group changes in body composition did reach statistical significance (calculated base on Kilen. 2015). At least in my humble opinion, though, they are still interesting.

Speaking of what people will deem relevant: We haven't addressed the changes in body composition yet. Why's that? Well, if we go by statistical significance, there were none. If we go by %-ages, though, the increase in lean and decrease in fat mass in the micro training, as well as the opposite trends in the classical training group add to the non-significant evidence that it may make sense to train more frequent and that - when all is said and done - total volume may eventually not be the only thing that matters... I mean, if you look at the data in Figure 2 it would - in defiance of the statistical insignificance of the changes - still seem as if the previously mentioned fitness model was right: For him or her, for whom improves body composition are the primary goal, his / her frequent AM/PM training regimen does in fact appear to be the training model of choice | Comment!

References:

• Kilen, Anders, et al. "Adaptations to Short, Frequent Sessions of Endurance and Strength Training Are Similar to Longer, Less Frequent Exercise Sessions When the Total Volume Is the Same." The Journal of Strength & Conditioning Research 29 (2015): S46-S51.