Thursday, March 2, 2017

Training Volume, Intensity, and Your Libido - How Bad is It? Who Read the Study Knows: It's not Just About Cardio ... !

Both, the male and female libido are at risk by overtraining. So don't continue your daily 1h stairmaster sessions, ladies!
You may have seen this study elsewhere on Facebook before... and I have to apologize that I am late to the party, but it disappeared in the "to write about" pile on my virtual desktop and resurfaced only today when I didn't find another recent study worth writing about.

Enough of the excuses, though. After all, the SuppVersity is the place to get all the study details - including an assessment of its practical relevance and a brief glimpse at relevant related research. What? No, I bet you didn't get that in one of the reposts to the abstract on PubMed, did you? Or did you understand what a low, medium or high "total intensity" was when you read those copy and paste jobs? It's not simply the VO2max. If you thought so, you probably misunderstood the study.
Overly frequent use of intensity techniques will also put you at higher risk of libido loss:

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Now, without further delay, let's take a look at what the study actually did. To study the associations between aspects of endurance exercise training and the sexual libido in healthy men using a cross-sectional online survey was conducted. Since this is the first study of its kind, a new online survey questionnaire had to be developed. As the scientists explain, ...
"[t]he questionnaire was based upon pre-existing validated questionnaires and use to assess elements of physical characteristics, exercise traininghabits and libido of participants (n=1077). Three evidence-based categories were created for the primary outcome of total libido score and low, normal, and high response categories set. The high and normal categories were combined to form a high/normal score group and the low category formed a low score group" (Hackney 2017). 
The fact that it "was based on pre-existing validated questionnaires", namely the ADAM, the SDI-2 and the AMS questionnaire for the libido-, and the IPAQ and the Baecke questionnaire for the physical activity, i  quite important. Even though this gives it an air of authority, we have to keep in mind that questionnaires can be pretty misleading (de Yébenes Prous 2009; Rosen 2004) and eventually the one at hand is non-validated - regardless of the excellent Cronbach's alpha of 0.70 to 0.96 (Tavakol 2011) and thus a high internal consistency of the individual constituents.
Table 1: The physical and exercise training characteristics of the participants (Hackney 2017).
If we assume that there were no built-in problems with the questionnaire, and appreciate that the scientists recruitment via sports clubs, national sports organizations, university athletic departments, and sporting magazines was decently successful (N = 1077 participants filled out the questionnaires | see Table 1 for participant data | mind the age groups: 1: < 18 years = not included in analysis; 2: 18-25; 3: 26-40; 4: 41-55; 5: ≥ 56), I guess we can live pretty well with the correlations the scientists calculated between their three evidence-based categories: duration, intensity of the workouts, age and total libido score (all featuring low, normal, and high response category sets).
Update on the significance of the results for women:On Facebook, Lillian rightly asked how I could claim that women would have to avoid hours of medium-to-high intensity cardio based on a study in men. Here's a brief reminder of what I've discussed in other articles about overtraining and the (female) athlete triad. There's very good evidence that - unlike resistance training - high(er) intensity long-duration "cardio" messes with the female reproductive system and female libido (Boyden 1983; Warren 1992 & 2001). Later this week I will discuss a recent study showing that this is not the case for frequent intense resistance training, though.
The fact that all participants were men, by the way, reduces the significance of the absolute results (i.e. the hours of exercise per week and the so-called "total intensity", but the general trend(s) should be similar for women). Unlike men, however, women will yet not just lose their libido (early phase), but also notice concurrent irregularities in their menstrual cycle (later phase | see red box above).
Table 2: Part of the dataset the scientists generated - I will dissect and discuss the relevant parts below (Hackney 2017).
A problem that we cannot ignore, though, is that the high and normal categories were combined to form a high/normal score group, while the low category formed a low score group before the odds ratios (OR = how likely is it that...) - to identify what "promotes" your libido is thus not possible. What we can tell, is what will keep you in either the normal or the high libido zone and that's:
  • low "chronic duration" (1-16h per week; 4-fold more likely) and medium "chronic duration" (20-40h per week; 2.5-fold more likely) compared to high "chronic duration" training (50 – 100h per week for years)
  • training at low "total intensity" (0-1100 VO2max x hours per week; 6.9-fold more likely) and medium intensities (1140-2480 VO2max x hours per week; 2.8-fold more likely) compared to subjects with a high "total intensity (2500-1000 VO2max x hours per week).
So what do you make of the results? Well, the total intensity was a computed variable representative of a number of training sessions at a low, moderate, hard intensity times the hours of each per week using the well-known VO2 cutoffs of low ≤35% of VO2max, moderate ~50% of VO2max, and high ≥70% of VO2max. 
Figure 1: Odds ratio of having a normal or high libido with low and medium duration, intensity, and age (Hackney 2017).
This is an important insight, after all, it goes against the notion that "steady state cardio [even walking on the treadmill as a cool-down] is generally bad" that many people who shared this post online evoked (deliberately or not) - a HIIT session of only 10 minutes at 95% of VO2max would, after all, generate a higher "total intensity" than a steady state session of walking at 30% of your VO2max on the treadmill if both had been done five times a week in the past five years which was the median value. 
Figure 2: Intensity and duration for different types of training done five times per week for five years plotted alongside the calculated "total intensity" values and information about the risk of libido loss (Hackney 2017).
In general, however, there's no debating, the highest "total intensity" levels are probably going to be generated by the typical "fat burning workouts" I have been criticizing for years, i.e. the 45-90 minutes on the treadmill at ~70% of your VO2max, in the alleged "fat burning zone". An even higher value would be observed for the Crossfit addict doing 5x60 min workouts powering the weights up and down at 80% of his/her VO2max per week (see Figure 2 for a comparison of the different exercise modes and the corresponding "calculated intensity").

Much easier to understand than the total intensity is the "chronic duration". Being computed as the arithmetic product of the time you spend in the gym or elsewhere doing any sports it is a simple proxy of your total training volume irrespective of the form and intensity of your training that - and this is important - does not involve the number of years you've been following this approach already (for me that is a questionable methodological choice the scientists made with the previously discussed "total intensity"). The unmistakable message here is: the more you work out on a weekly basis (or the less you recover per workout hour?), the higher your risk will be.
Could something as simple as a saliva test tell you if you or your clients are overtraining? I mean, common sense would dictate that cortisol, free T and IL-6 should tell us something. Learn more in my 2016 article "Overtrained or in the Zone? Tests & Analyses of Samples of Athletes' Saliva Shall Help Determine Objective Criteria" | more
So, you better limit your weekly sports activity to 16h total!? True, that's the message the non-exercise and non-intensity specific "chronic duration" data sends. If you train more than 50hrs per week your risk of suffering from a low libido is maximal. On the other hand, people who train only 20-40h per week and 1-16h per week are 4x and 2.5x more likely to have either normal or even high libido ratings on the subjective tests that were used in the test at hand.

The "total intensity" data, on the other hand, is hard to interpret. It mixes training volume, intensity, and number of the years of sticking to this madness. So, don't remember the actual figures, but rather the following interpretation: the higher your intensity, the lower your training frequency, training time and the time you stick to this intensity withing your year-long periodization regimen should be.

Practically speaking this means: Yes, you can CrossFit or do the classic 1h cardio regimen five days a week for some time, but you should know that after months and years this is going to crush your libido, while 5x20 minutes walking or doing 5x10 minute of HIIT at 95% of your VO2max are not that likely to induce the same libido reduction | Comment!
  • Boyden, Thomas W., et al. "Sex steroids and endurance running in women." Fertility and sterility 39.5 (1983): 629-632.
  • de Yébenes Prous, M. Jesús García, Francisco Rodríguez Salvanés, and Loreto Carmona Ortells. "Validation of questionnaires." Reumatología Clínica (English Edition) 5.4 (2009): 171-177.
  • Hackney, Anthony C., et al. "Endurance Exercise Training and Male Sexual Libido." Medicine and science in sports and exercise (2017).
  • Rosen, Raymond C., et al. "Male Sexual Health Questionnaire (MSHQ): scale development and psychometric validation." Urology 64.4 (2004): 777-782.
  • Tavakol, Mohsen, and Reg Dennick. "Making sense of Cronbach's alpha." International journal of medical education 2 (2011): 53.
  • Warren, MICHELLE P. "Clinical review 40: Amenorrhea in endurance runners." The Journal of Clinical Endocrinology & Metabolism 75.6 (1992): 1393-1397.
  • Warren, M. P., and N. E. Perlroth. "The effects of intense exercise on the female reproductive system." Journal of Endocrinology 170.1 (2001): 3-11.