Detraining and Training Periodization: 6 Months On "Six Weeks On + Three Weeks Off" Macrocycle Yields Identical Gains Strength and Size Gains as Continuous Training

"Is everyone at home taking some time off to recover + prime future muscle growth?"

Human beings are creatures of habit. This is particularly true, when it comes to those things and procedures we either like or enjoy or have found to be highly conducive to our goals, in the past. Just like some people simply won't drop their beloved Twinkies and Ding Dongs, although they know that these sugar bombs are bad for them, and others tend to stick to whatever dietary regimen has allowed them to lose 20lbs of body weight in the past, despite the fact that this "trick" has long ceased working for them, many "recreationally active" individuals (aka gymrats) are totally reluctant to any form of carefully planned deviation of their training regimen.

Six weeks on, three weeks off - for better or for worse!?

If anything, switching gears from a more hypertrophy to a more strength training oriented program, or vice versa, is probably the one modification most trainees could come to terms with. The notion to take one, let alone three weeks off after the completion of a 6 weeks mesocycle, on the other hand, scares the hack out of 99% of the ambitious strength trainees. Unjustly, as a study that's been published less than one week ago in the online edition of the European Journal of Physiology goes to show you (Ogasawara. 2013).

Systematically periodized trainig routines (yet often with only one detraining phase per season) are among the various reasons professional athletes are at a lower risk of developing the athletes' triad than overambitious gymrats.

As surprising as it may sound to the "I will lose my precious muscle" faction, the results of the study Riki Ogasawara and his colleagues from the University of Tokio conducted do actually just confirm what we knew all along:

"[A]fter short-term (>1 month) cessation of training (detraining), muscle adaptation responses may return to their initial levels, and the effects of retraining after short-term cessation on muscle growth are comparable with those observed during the early phase of training." (Ogasawara. 2013)

If we further acknowledge that the loss of protein from the muscle during the detraining phase is much slower than the rapid gain, during the early weeks of (re-)training, it should be obvious that any retraining phase will lead to overall increments in skeletal muscle cross sectional area that will easily overcompensate the small amount of size your muscles will have lost during the comparatively short phase without physical exercise.

Based on the actual results of previous research by Narici et al, Bemben et al. Hakkinen et al. and Hulmi et al., Ogosaware et al. propose the following example to illustrate this effect:

*Why is it problematic that the study participants were untrained? With the initial growth response to weight training being much more pronounced in previously untrained individuals, it is very likely that the same is going to be the case for the similarly pronounced response to "retraining" after a three-week detraining phase. This does not generally speak against the usefulness and maybe even the need for well-planned periodization in advanced trainees, but it renders the concept of a complete three weeks lay-off (=classic detraining) at least questionable. Read my comments towards the end of this post for possibly better-suited alternatives.

"[...] assuming that the decrease in thigh muscle CSA during 3 weeks of detraining is 2.1 % (estimated at 0.10 % per day and 21 days), and the increase in muscle CSA during 6 weeks of retraining is 5.9 % (estimated at 0.14 % per day and 42 days), the increase in muscle CSA during a 3-week detraining/6-week retraining period (estimated at 0.06 % per day during 9 weeks) would be 3.8 %. The estimated value of 0.06 % per day is similar to values obtained in previous studies, where the average increase in thigh muscle CSA was reportedly around 0.05 % per day." (Ogasawara. 2013)

Well, I see this alone can't convince you, right? What about the detailed results of Ogasawara very own study, then? Allegedly, it was done in untrained individuals*, 14 young men (age 25 ± 3 years, standing height 1.72 ± 0.06 m, body mass 65 ± 10 kg), but the results the training regimen the researchers characterize as follows,

"Both groups performed high-intensity, free-weight bench press exercise training 3 days per week. [...] Training intensity was set at 75 % of one repetition (rep) maximum (1-RM), and training volume was set at 3 sets of 10 reps (with 2–3 min rest between sets). To ensure an adequate training load, all training sessions were overseen by a supervisor. Training load was renewed every 3 weeks, and, if subjects could perform 12 reps or more at the 3rd set during training sessions, the training load was increased by about 5 % for the next training session." (Ogasawara. 2013)

speak for themselves and were virtually identical in both groups - regardless of whether the subjects trained for 24-weeks continuously (CTR), or performed their regimen in the form of two cycles of 3-week detraining/6-week retraining periods after an initial 6-week mesocycle.

Figure 1: Relative changes 1-RM and maximal voluntary contraction (MVC) + time-course of these changes (left); time-course of relative changes in cross sectional area in triceps bracchii (top, right) and pectoralis major (bottom, right; based on Ogasawara. 2013)

Aside from the already mentioned training status of the study participants there are yet two other things I am missing in this study:

Figure 2: Just in case you've forgotten about that - different muscles react in different ways to modulations in training volume. So why would they react identically to off-times? Moreover if legs benefit most from a higher training volume, wouldn't it be likely that they suffer most from longer periods of detraining?

1. Detailed data on the pre / post body composition. The identical increase in body weight (+2%) is not of interest to me (and probably to only very few of you) and the simple assumption that identical body weight gain + identical CSA gains of triceps brachii (TB) and pectoralis major (PM) would translate into identical changes in total body fatness / muscularity is about is unwarranted (see link in figure 2).
2. A realistic full-body workout routine: The low volume chest only workout regimen is not just unrepresentative of a real workout protocol, it does also raise the question if other body parts as the legs, for example, would not respond very differently to a three week lay-off phase (see figure 2 + respective reference to a previous post on training volume).

As far as the pectoralis and triceps specific gains in muscle size and strengths in strength training newbies are concerned, the results of the study at hand do however add  o the initially mentioned practicability of a simplistic, but effective "6 weeks on, 3 weeks off" approach to periodization, which - and this is a novel finding compared to Ogasawara's study from last year (Ogasawara. 2011) - does still work even in the third mesocycle (take another look at figure 1 the "catch up growth" does not diminish!).

Conclusion + "What about advanced athletes?"

Despite the fact that the last mentioned sustainability of this approach over a pretty long time period (24 weeks, i.e. 3x complete macrocycles) would indicate that a similar approach will work for trained (maybe even elite) athletes as well, I am pretty convinced that a period of three weeks of complete idleness is not the optimal periodization strategy for advanced trainees, because:

Possible alternatives for advanced athletes: Rather than taking a complete 3-week time out from all athletic endeavors, you can to stick to ...

• a maximal complete off-time of 1-week (as in not doing anything), 
• a 2-3 weeks of active off time (as in going on vacation w/ regular non-exhaustive physical activity), or
• the incorporation of a tapering regimen as described in Part VI of the Step By Step Guide to Your Own Workout

Alternatively you can combine / mix one or two of these (you won't go on vacation every 6 weeks, will you?)

• The discrepancy between the accrual of skeletal muscle protein and the loss of the latter in response to total laziness gets lower, if not totally reversed, the bigger you get. Consequently the added bonus of "faster gains" upon recommencing the training will diminish, or even disappear completely.
• Many more or less "professional" trainees follow dietary regimen that are not sustainable, when they are not training. During a complete time-off of three weeks without any alternative "outlet", the chances to gain fat are thus much higher for them, than for the average beginner, who - if anything - guzzles a protein shake after each of his three weekly training sessions.
• Competitive amateur athletes who are training 5x a week or more actually run the risk of both, physical and psychological withdrawl symptoms, when they simply stop training altogether (another argument in favor taper, if you asked me; see infobox on the right).

Regardless of which of the alternatives in the blue infobox next to the three arguments that make a complete 3-week lay off at least questionable for advanced / professional trainees you pick, if you decide against the "No, that's bullocks, I train day-in-day-out till I drop" approach, there is one thing you should keep in mind:

If you are not the one in a million expection from the rule,
you cannot simply "play this by ear"!

Periodization requires planning and planning is done in advance and not in a "well, I feel like I could go for another week" or "damn, I am tired today, let's take three weeks off and see how it goes then" fashion. Alright?

References:

• Bemben DA, Fetters NL, Bemben MG, Nabavi N, Koh ET. Musculoskeletal responses to high- and low-intensity resistance training in early postmenopausal women. Med Sci Sports Exerc. 2000: 32:1949–1957
• Hakkinen K, Newton RU, Gordon SE, McCormick M, Volek JS, Nindl BC, Gotshalk LA, Campbell WW, Evans WJ, Hakkinen A, Humphries BJ, Kraemer WJ. Changes in muscle morphology, electromyographic activity, and force production characteristics during progressive strength training in young and older men. J Gerontol A Biol Sci Med Sci. 1998; 53:B415–B423
• Hakkinen K, Alen M, Kallinen M, Newton RU, Kraemer WJ. Neuromuscular adaptation during prolonged strength training, detraining and re-strength-training in middle-aged and elderly
  people. Eur J Appl Physiol. 2000; 83:51–62.
• Hakkinen K, Alen M, Kraemer WJ, Gorostiaga E, Izquierdo M, Rusko H, Mikkola J, Hakkinen A, Valkeinen H, Kaarakainen E, Romu S, Erola V, Ahtiainen J, Paavolainen L. Neuromuscular adaptations during concurrent strength and endurance training versus strength training. Eur J Appl Physiol. 2003; 89:42–52
• Hulmi JJ, Kovanen V, Selanne H, Kraemer WJ, Hakkinen K, Mero AA. Acute and long-term effects of resistance exercise with or without protein ingestion on muscle hypertrophy and gene expression. Amino Acids. 2009; 37:297–308.
• Narici MV, Hoppeler H, Kayser B, Landoni L, Claassen H, Gavardi C, Conti M, Cerretelli P. Human quadriceps crosssectional area, torque and neural activation during 6 months strength training. Acta Physiol Scand. 1996; 157:175–186
• Ogasawara R, Yasuda T, Sakamaki M, Ozaki H, Abe T. Effects of periodic and continued resistance training on muscle CSA and strength in previously untrained men. Clin Physiol Funct Imaging. 2011 Sep;31(5):399-404.
• Ogasawara R, Yasuda T, Ishii N, Abe T. Comparison of muscle hypertrophy following 6-month of continuous and periodic strength training. Eur J Appl Physiol. Oct 06, 2013. 

Want to Cut 12% Body Fat in 12 Weeks, Get Stronger, Bigger or Better Conditioned? Periodize Appropriately!

Image 1 (hitchfit.com): I know I am repeating myself, here, but 12% less body fat mass in 12 weeks without dieting should be a reason to pick up those dumbbells, ladies, right?

If you have read Adelfo's blogpost, yesterday, you will have noticed the versatility of his routine. The combination of volume, 5x5 and EDT training, which may appear somewhat chaotic at first, is yet well-planned, clearly structured and has little of the "cookie-cutter" approach to training people follow who will tell you in the locker room, whenever you meet them: "Ah, I better train biceps today, my legs don't feel right, bro" ;-) In the end, Adelfo's approach is just an unconventional twist on undulating periodization; in other words, a training split where you switch your rep and set numbers in relatively short (but regular!) intervals - often from one training to the next. But is this really the optimal way to train? I mean HST = hypertrophy specific training looks different and that is "hypertrophy specific", right? And in fact, if analyzed on its own, a recently published study from Brazil appears to suggest that what Adelfo feels is the best way to train could in fact be inferior to a less sophisticated linear periodization program  (de Lima. 2013). - and you know what? At least for his sedentary cousin that may in fact be right!

Lifting weights works! Regardless of how you periodize, but...

The 28 healthy, normal-weight, formerly sedentary women (age 20–35; body fat ~25%) from the de Lima study had been randomly assigned to follow 2-day body split routines which differed only with respect to the means of periodization, i.e. the sequence of lower vs. higher rep work (see illustration 1 for an outline of the training regimen) for 12 weeks (no dietary changes or other inventions).

Illustration 1: Outline of the workout (left) and periodization regimen (right) the 28 young women followed over the course of the 12-week intervention period (de Lima. 2013)

If we based our predictions on previous data in 28 recreationally trained college-aged men (Buford. 2007), 40 young men (21.5y) with a minimum 1-year strength training experience (Prestes. 2009a) and 20 resistance trained men (26y; 4-5 years of training experience; Miranda.. 2007) both conducted with linear vs. undulating periodization schemes in the strength-to-hypertrophy rep ranges of 4-8 and 4-14 reps, respectively, we would expect either no difference (Buford. 2007) or a slight advantage for the undulating periodization protocol with respect to its effects on maximal strength (Prestes. 2009 a,b).

Figure 1: Rel. changes in body composition, maximal strength and strength endurance (de Lima 2013)

As the data in figure 1 shows, neither of those predictions is accurate. Contrary to Buford et al. de Lima et al. did observe statistically significant differences between the study arms, yet other than Prestes et al. those changes were not in the maximal strength, but rather in the strength endurance domain. And while the latter showed significantly greater improvement in the women who trained according to the undulating periodization protocol, the classic, some people would probably say "boring", linear periodization protocol elicited a substantially more pronounced decreases in body fat and increases in strength.

Periodicize according to your training level & goals

As boring as those highly structured linear periodization protocols may be, the results from the de Lima study would suggest that there is a reason why Brian Haycock's HST (=Hypertrophy Specific Training) periodization prescriptions are downright anal. It is also reasonable to assume that for beginners and (early) advanced trainees, long(er) cycles will allow for optimal structural adaptations to the individual loading patterns, with the "growths" phases in the medium (8-12) rep ranges and facilitative strength gains and endurance gains in the lower-rep (4-6) respectively higher rep (15-20) weeks. It is also interesting to note that in these early days, when trainees makes the transition from undermuscled couch potato to "recreationally active" muscle gains and fat loss are coupled and can, as the data from the de Lima study shows, be influenced not just by modulating the total number of sets (volume) or the rep range, but also by changing the sequence of phases of training at the upper, medium and lower range of a given set x rep continuum (here 3x15-3x30) - that the latter was somewhat higher than normal (here "normal" indicates 6-15), may have exerted confounding effects, but it does not take away from the constantly overlooked, yet non-negligible effects different means of periodization exert on both your performance and your body composition!

Chest	Biceps	Back	Core	Legs	Triceps	Shoulders
Navigate the SuppVersity EMG Series and learn about the best exercises for a given body part (incl. example workouts).

The studies by Buford Miranda and Prestes on the other hand, suggest that those facilitative strength and strength endurance gains, without which no strength trainee, rookie, advanced or veteran will be able to generate the necessary overload to cause structural adaptations, or put simply, skeletal muscle hypertrophy, may require a slightly more creative, yet by no means chaotic workout organization, once you have a couple of years of weight lifting under your belt.

Daily vs. weekly undulation? I am with Dr. Hatfield and prefer the former!

Personally I prefer the intra-workout or as Miranda et al. call it "daily undulatory" periodization à la Dr. Squat (Hatfield): It makes training more fun and allows me to perform every exercise and train for every body part in a rep range of which I feel that it suits it best:

• lower rep work and a focus on continuously increasing the poundage on compound exercises, such as the squat, deadlift, bench press, military press, pull ups and bend over rows at the beginning of my workouts or as the first exercise for a given body part
• medium and sometimes high(er) rep work and a focus on maximal muscle tension on auxiliary exercises such as biceps curls, triceps extensions, flys, cable cross, pullovers, seated rows, dumbbell rows, reverse DB/cable flys, side laterals, upright rows and shrugs in the latter part of my workouts or as follow up exercises for a given body part

And though Miranda et al. may not have found statistically significant differences in any of the individual tests the 20 strength training veterans in their study had to perform, the greater effect sizes in the undulating periodization group (1.54 = large for daily undulating periodization vs. 1.04  = moderate for linear periodization) appear to prove my instincts and training experience right ... but to be honest, even if it didn't I would rather train "suboptimal" than bore myself to death during another HST (=linear periodization) cycle.

Ressources:

1. Buford TW, Rossi SJ, Smith DB, Warren AJ. A comparison of periodization models  during nine weeks with equated volume and intensity for strength. J Strength Cond Res. 2007 Nov;21(4):1245-50. 
2. de Lima C, Boullosa DA, Frollini AB, Donatto FF, Leite RD, Gonelli PR, Montebello MI, Prestes J, Cesar MC. Linear and Daily Undulating Resistance Training Periodizations Have Differential Beneficial Effects in Young Sedentary Women. Int J Sports Med. 2013 May 4
3. Miranda F, Simão R, Rhea M, Bunker D, Prestes J, Leite RD, Miranda H, de Salles BF, Novaes J. Effects of linear vs. daily undulatory periodized resistance training on maximal and submaximal strength gains. J Strength Cond Res. 2011 Jul;25(7):1824-30.
4. Prestes J, Frollini AB, de Lima C, Donatto FF, Foschini D, de Cássia Marqueti R, Figueira A Jr, Fleck SJ. Comparison between linear and daily undulating periodized resistance training to increase strength. J Strength Cond Res. 2009 Dec;23(9):2437-42.
5. Prestes J, De Lima C, Frollini AB, Donatto FF, Conte M. Comparison of linear and reverse linear periodization effects on maximal strength and body composition. J Strength Cond Res. 2009 Jan;23(1):266-74.

Tapering 101: What It Is, How It's Done and Why It Works. Plus: Why Tapering & Detraining Are Not Interchangeable

Tapering is a must for professional athletes before an event like the Olympic games. Many recreational trainees think of more as a necessary evil that should at least be able to replace the dreaded detraining phases... little do they know.

Since the feedback on yesterday's post on detraining tells me that this is a topic of interest for the majority of SuppVersity readers (which it incidentally should be), I thought I'd follow this up with a brief review on tapering, which is often falsely considered as a "not so hardcore" alternative to keeping away from the gym all-together. While detraining means exactly what the word implies "away from training", tapering is usually described as "the training phase characterized by a  reduction of the amount of training that athletes undergo" (Mujik. 2010), which is often timed before the final days leading to a major competition.  In that it is up to the athlete / trainer to pick whether he/she wants to alter the training volume, intensity, and frequency, whether he / she picks a progressive or step taper (Bosquet. 2007).

Beware of the cookie cutters and take responsibility for your training success and failure

If this is not your first visit to the SuppVersity, you should be aware of my take on "cookie-cutter approaches", when it comes to exercise, nutrition and supplementation: They suck! That being said, I will try my best to provide you an overview over the available evidence, so that you can decide on whether or not you will benefit from tapering and what may be the most suitable form for you as an individual. The person to answer above question, specifically the latter part of it, namely "which one is best for me?" will therefore be no one else than you!

"Ok, which methods of tapering are there and which one is best for me?"

That tapering is a viable strategy to increase exercise performance is indisputable and has in fact been shown for various types of sports which range from running, over swimming and cycling up to triathlon. Tapering (or similar protocols) is likewise common practice in almost all team sports activities, such as football, soccer, basketball etc. In view of the tight on-season schedule of team sport athletes, these tapering periods are yet not part of the day-to-day business. The basic idea behind a taper is, as Bosquet et al. aptly put it, ...

"[to] maximize the decrease in accumulated fatigue while retaining or further enhancing physical fitness, thus leading to peak performance." (my emphases in Bosquet. 2007)

Contrary to a detraining period, of which we have learned yesterday, that it is supposed to maintain / increase the long-term output of your training regimen. Tapering aims at acute peak performance and is therefore not a replacement, but a complement to regular detraining periods in your training cycles.

Intensity , volume, frequency - the common set-screws for tapering

I've mentioned the three main parameters athletes and trainers will be modulating, when they taper in the introduction, already (intensity , volume and frequency), and while there is an overall scientific consensus that all of them can be beneficial, the extend to which each of this is supposed to be reduced is still highly debated:

Ronnie Coleman is just one of the pros who trained with crazily high volume and weights. If like to train similar, tapering alone won't cut it. Detraining is a must if you want to keep the anabolic response to workouts like these intact (read more)

• intensity reductions are interestingly less common than you would think, in a previous study I wrote about, here at the SuppVersity a taper with a very low volume, but higher intensity did yield beneficial results (read more)
• volume reductions range from ~10%-85% of the original training volume and are the "standard" set screw during a taper; oftentimes reductions in volume are yet accompanied by other twists, like a higher training frequency, or heavier weights / training intensity for special purposes
• frequency reductions are particularly indicated for people who train more than three times a week, everyone else would probably be better advised to reduce the overall training volume by making each of the sessions shorter (remember: tapering is a training strategy that's mostly employed by serious, but not necessary "professional" athletes, and those people don't train just 2 times per week ;-)

Additionally the length of the taper, which is usually around two weeks will obviously be a confounding factor of the degree of intensity, volume or frequency reductions that will be necessary to elicit the desired performance improvements. In that, tapering regimen as short as 7 days have been shown to increase 40km time trial performance in trained cyclist via its beneficial effects on cytochrome oxidase expression and succinate dehydrogenase levels in the type I muscle fibers (Neary. 2003).

More tapering does not yield more benefits - there is, as usual, a happy medium

Mujika et al., on the other hand, have shown that an extended taper of four vs. just three weeks yielded an additional increase in performance gains. During a 6-week taper, however, the "peak" increase of +3% that occurred after four weeks of tapering could not be sutstained (Mujika. 1996).

Figure 1: Effect sizes calculated based on 27 studies; green bars indicate stat. significant and "optimal" strategies, orange bars indicate likewise significant or borderline significant alternatives, blue bars indicate non-significant effects and the red bars should tell you that you better keep away from messing with these parameters (based on Bosquet. 2007)

If you take a look at the effect sizes Bosquet et al. calculated in one of the few, if not the only large scale meta-analysis (including 27 studies), the "optimal" strategy appears to taper by reducing your training volume by at least 21-40% - better make it 41-60%. Practically speaking, this would mean

• if you usually do 10 HIIT intervals, you would now do five, 
• if you usually do two exercises per body part, you will now do one, 
• if you usually do steady state cardio for 40 minutes you hop of the treadmill after 20min, now

Since the optimal duration appears to be two weeks, an additional and in fact often used tweak to the regular single-step progression would be to drop down by 50%  in the first week and then increase you training volume by 25-50% (of the reduced volume) in week two. If you decided to go for a 50% on-ramp you would thus do 7-8 intervals, 2 exercises for the larger muscle groups, one for the small ones, and cardio for 30 min. Yet despite the fact that this two- or more-step tapering is common practice within the athletic community, it has as of now not been confirmed in peer-reviewed studies that the "ramp" before the peak will produce greater performance increases, than the classic one-step drop (Bosquet. 2007).

What does actually happen during a taper?

Now that we did shed some light on the practical side of things, let's briefly take a parting look at what the research says about the underlying mechanism that's behind the performance increment after a taper. As Bosquet et al. point out in their excellent meta-analysis:

NaHCO3 loading is less taxing on your digestive tract and is an effective strategy to increase your performance during both high intensity sprints and high volume resistance training. Learn more about NaHCO3 loading for cyclists and it's beneficial effects on "old-school" high volume resistance training. Don't be fooled, though, no dietary supplement will make tapering and detraining obsolete!

• increased VO2max due to taper-induced hypervolemia and enhanced red cell production and an increase in oxidative enzyme activity
• reduced  energy cost of exercise is another possible explanation, which has yet not observed in all of the few studies that even tested for it; there are respective reports for swimming and running; according to Houmard et al. the most likely cause of these beneficial adaptations are of biomechanical and neural origin (Houmard. 1994); this hypothesis is also supported by more recent research
• increased aerobic endurance due to improved contractile and metabolic properties of the muscle fiber, yet probably not due to fiber type transitions; additional increases / supercompensation effects pertaining to the intramuscular glycogen stores may also contribute to the aerobic (and strength) endurance increases

I know you are missing bodybuilding / strength training specific data, right? Well, this is a simple result of the fact that tapering is a typical endurance training thing and imho it is that for two reasons, namely:

Go back to yesterday's post about the effects of detraining if you are still afraid of losing muscle from taking 1-2 weeks off.

1. It is unlikely that tapering will yield similar restorative effects on the hypertrophy response to your workouts as they were observed in the detraining study that was in the news, yesterday.
2. Any sane periodized strength training program does already have built-in "tapering" and "detraining" phases, which are yet rarely labeled as such - think of the "deconditioning" phases in the infamous hypertrophy specific strength training (HST), or the periodic cycling between high volume, medium intensity and high intensity low volume training.

The scarce literature on the effects of "tapering" on resistance training performance does yet suggest that the latter is the preferred strategy in longer phases (>3 weeks), in which your time-schedule simply does not allow you to spend as much time in the gym as usual, as it will preserve lean mass and performance compared to longer phases of detraining (Gibala.1994).

Tapering to bridge time-periods, where you cannot make it to the gym as often

The 2007 study by Izquierdo et al. I discussed in Part VI of the Step By Step Guide to Your to Your Own Training Regimen does confirm the notion that a high intensity, low volume tapering regimen (in and out of the gym in less than 20min) would be the appropriate strategy to maintain performance during periods, in which you cannot muster the time to perform your regular workout routine.

The fact that the researchers also observed that only detraining, yet not tapering increased the IGF-1 levels of the participants, does yet confirm the fact that tapering and detraining are not interchangeable. While the former will give your body time to recuperate, it probably cannot replace detraining the 1-2 week phases of detraining or "strategic deconditioning" which should be an obligatory part of your training regimen.

---

Bottom line(s): Per definition, the best time to "taper" is before a meet or competition. It could also help you peak before a bodybuilding show or photoshoot, as it will support a more muscular and less "watery" look that often comes with the glucose depleting and muscle damaging high volume (+high intensity) routines.

According to what we know now, 2-3 weeks of tapering appear to yield the most pronounced benefits. In that, it should be obvious that the way you taper will determine the optimal length: A low volume high intensity taper, for example, can also help maintain muscle mass over longer periods of time, whenever your "real life" does not allow you to train as regularly as usual.

Tapering and detraining both have their place in your training regimen, in which "inverse tapering" aka "retraining" may provide a third way to increase your gains (read more)

The best way to use and combine the individual set-screws volume, intensity and frequency has yet to be determined. It is likely to be highly sport specific and will definitely depend on the training regimen you were on before the taper. A 40%-60% reduction in training volume does yet stand out as the common denominator of successful tapering interventions. Concurrent increases in training intensity can make sense especially for strength, yet probably not so much for endurance athletes. Changes in training frequency are less promising. If you do yet train more than 4 times per week or in AM and PM sessions, it would appear prudent to cut volume by simply dropping down to to three workouts per week.

Don't use tapering to replace the obligatory back-off week(s) = detraining. Both the effects, as well as the underlying mechanisms are different. If you switch back between more strength and more hypertrophy oriented periods of strength training, it may make sense to do a high intensity taper after the hypertrophy phases to precondition your body for the strength phase and take 1-2 weeks off (detraining) after the ensuing strength period to return to the gym with an optimal growth response.

References:

• Bosquet L, Montpetit J, Arvisais D, Mujika I. Effects of tapering on performance: a meta-analysis. Med Sci Sports Exerc. 2007 Aug;39(8):1358-65.
• Gibala MJ, MacDougall JD, Sale DG. The effects of tapering on strength performance in trained athletes. Int J Sports Med. 1994 Nov;15(8):492-7.
• Hooper SL, Mackinnon LT, Ginn EM. Effects of three tapering techniques on the performance, forces and psychometric measures of competitive swimmers. Eur J Appl Physiol Occup Physiol. 1998 Aug;78(3):258-63.
• Houmard JA, Costill DL, Mitchell JB, Park SH, Hickner RC, Roemmich JN. Reduced training maintains performance in distance runners. Int J Sports Med. 1990 Feb;11(1):46-52. 
• Houmard JA. Impact of reduced training on performance in endurance athletes. Sports Med. 1991 Dec;12(6):380-93. Review. 
• Houmard JA, Hortobágyi T, Johns RA, Bruno NJ, Nute CC, Shinebarger MH, Welborn JW. Effect of short-term training cessation on performance measures in distance runners. Int J Sports Med. 1992 Nov;13(8):572-6.
• Houmard JA, Scott BK, Justice CL, Chenier TC. The effects of taper on performance in distance runners. Med Sci Sports Exerc. 1994 May;26(5):624-31.
• Izquierdo M, Ibañez J, González-Badillo JJ, Ratamess NA, Kraemer WJ, Häkkinen K, Bonnabau H, Granados C, French DN, Gorostiaga EM. Detraining and tapering effects on hormonal responses and strength performance. J Strength Cond Res. 2007 Aug;21(3):768-75.
• Mujika I, Busso T, Lacoste L, Barale F, Geyssant A, Chatard JC. Modeled responses to training and taper in competitive swimmers. Med Sci Sports Exerc. 1996 Feb;28(2):251-8.
• Mujika I. The influence of training characteristics and tapering on the adaptation in highly trained individuals: a review. Int J Sports Med. 1998.
  
• Mujika I. Intense training: the key to optimal performance before and during the taper. Scand J Med Sci Sports. 2010 Oct;20 Suppl 2:24-31.
• Neary JP, Martin TP, Quinney HA. Effects of taper on endurance cycling capacity and single muscle fiber properties. Med Sci Sports Exerc. 2003 Nov;35(11):1875-81.
• Thomas L, Busso T. A theoretical study of taper characteristics to optimize performance. Med Sci Sports Exerc. 2005 Sep;37(9):1615-21.