Strength, Cardio or Both? Study Sheds Light on Which of the Three Generates the Highest Testosterone to Cortisol Ratio. Plus: Why it May not Even Matter

Image 1: Best to be used on non-strength training days for an intense HIIT session or some regenerative cardio, these machines probably don't hamper your progress as much as bro-science would have it - even if you use them after your strength workout.

I would venture the guess that the earth-shattering recognition that testosterone-induced acute increases in protein synthesis are not the fundamental determinant of the sex-differences with respect to the ability to acquire lean muscle mass (cf. "45x More Testosterone"), did not unsettle your faith in the anabolic properties of the Big T (as discussed in "Zoning in on the Big T"). You will therefore probably be inclined to read my summary of the results of a recently published study that was conducted by scientists from the Department of Sports Physiology, Science and Research Branch in Teheran, Iran, which dealt with the differential effects of strength, endurance and concomittant strength and endurance training on the testosterone and cortisol levels of 24 previously untrained men (22y; 76kg; VO2Max 43ml/kg/min).

Strength, cardio or both? That is the question!

We have dealt with similar topics in the past, here at the SuppVersity. Those of you who have been around for some time, will remember the 2011 study by Sahlin et al. which showed that a bout of resistance training, when would increase mitochondrial biogenesis and protein synthesis and ramp up your fatty acid metabolism, when it was performed right after an endurance training session (cf. "Doing Legs after Cardio"). On the other hand, the results of a more recent study by Rosa et al. did suggest that doing weights first would be the way to go - at least if your focus was on keeping your leptin levels up (cf. "Greater Reductions in Leptin with Weights After Cardio"). And as if things were not yet complicated enough, a much-cited meta-review by Wilson et al. appears to suggest that neither one nor the other would be a good idea (Wilson. 2011).

The study protocol: Periodized strength or "HIIT" vs. both

In the study at hand (Shakeri. 2012), Nader Shakeri and his colleagues assigned their 24 participants, who had been randomly selected from a group of 86 volunteers, to one out of three homogeneous groups. Thusly, the scientists made sure that there were no statistical siginficant differences in terms of body composition, VO2max, etc. between the three study arms:

1. Endurance (interval) group: Three times per week the participants performed 4, 6 and 8 bouts of 3min cycling at 75%, 80% and 85% of their maximal heart rate in weeks 1-4, weeks 5-8 and weeks 9-12 respectively. This "quasi-HIIT" program, which obviously got intense, because the intervals were so longish, but is otherwise still different from e.g. my HIIT prescription in the templates I have provided in the last installment of the "Step by Step Guide to Your Own Workout", was preceded by an initial 5-min warm-up at 60W and followed by a short cool down [Note: There is no information about the rest periods between the intervals].
    
2. Resistance training group: Brief warm-up, followed by a standardized leg-training routine consisting of 3 sets with 12, 8, 6 repetitions of leg presses, the leg extensions, leg curls and adductor and abductor exercises at 70%, 80% and 85% of the 1RM with 3min rest between sets; training loads were progressively increases over the 12-week study period in the course of which all participants trained three times per week.
    
3. Concurrent training group: Same as endurance training, yet only half of the workload, with sessions comprising only one set of 10 reps of each exercise at 80% or the 1-RM and 2, 3 and 4, instead of 4, 6 and eight bouts of cycling at the given VO2max (see endurance training group for details; note: it is not quite clear from the study text, but it appears as if the strength training was performed first)

With the workload reduction in the strength and endurance components of the concomitant training group it does not really come as a surprise that the haemoglobin (Hb) and hematocrit (Hct) levels did not differ between the groups. After all, the dreaded reductions in "iron", as it is often called, are usually directly related to mostly exaggerated workloads.

Strength for T (testosterone), both for C (cortisol)

The testosterone and cortisol responses on the other hand, are also influenced by the type of training you perform. It is thusly not really surprising that we do see an increase in total testosterone in the strength training group.

Figure 1: Total testosterone (ng/ml) and cortisol levels (nmol/ml) - left; and total testosterone to cortisol ratio - right (data adapted from Shakeri. 2012)

What may yet come as a surprise are the decreasing cortisol levels in both, the endurance only and the strength training only groups and the magnitude by which the total testosterone levels of the subjects in the endurance group plummet after the 8x 85% "HIIT" sessions in week 9-12 (cf. figure 1).

Total or free testosterone - you better test for the right one!

If we consider only, the total testosterone levels (TT), conventional wisdom (see discussion at the end of this post) about the importance of the TT-toortisol (TT/C) would dictate that the high workload in weeks 6-12 would counter, or at least mitigate the beneficial effects of resistance training. After all, the TT/C ratios are significantly lower than at baseline in all, but the concurrent training group, in which the standard variation of ~50% was too large for the data to reach statistical significance (cf. figure 1, right).

Figure 2: Free testosterone (pg/ml) and free testosterone to cortisol ratio (data adapted from Shakeri. 2012)

If we use the free testosterone levels as a reference, though, a very different picture emerges (cf. figure 2). While neither the endurance, nor the concomitant training had any (statistically significant) impact on the latter, the FT/C ratio of the subjects in the strength only group increased by ~33% (p < 0.05 despite yet another >50% standard deviation).

So, Wilson was right? Never do cardio after weights?

As I have already hinted at between the lines, the ostensibly straight-forward conclusion that these results would simply confirm what the bros have been preaching for years, i.e. "Never to cardio after weights - regardless of the type and/or volume!", is more than debatable in view of the results from Stuart Phillips' lab at the McMaster University in Canada, Ontario. After all, in their 12-week resistance exercise training study, West and Phillips found no correlation for either strength or size gains with free testosterone, but a weak yet statistically significant correlation between increases in lean body mass and cortisol (West. 2011)!

Figure 3: Correlations (blue) and p-values (red) between serum hormone levels and increases in lean body mass in the West & Phillips 12-week resistance training study (based on data from West. 2011)

Despite differences in the groups under study, the evaluation procedures, the type of training and maybe most importantly the time of blood collection (in the study at hand in the morning before the next training session) and the gap between the training sessions, the current study does thusly not provide conclusive evidence for nor against concomitant strength and endurance training. If we put more faith in the correlations West and Phillips observed in their trial (cf. figure 3), than in the bro-scientific assumption that "cortisol is the devil", though, it appears that - aside from doing HIIT on an individual day - the combination of a higher volume (=higher than the one set per exercise in this study) strength training with a lower volume (4-5 intervals) higher intensity (all out, but shorter) or a more regenerative type of cardiovascular activity, could not only help you make leaner, but maybe even more pronounced gains in lean body mass - probably yet not because of maximal cortisol levels, but rather because of a maximal training stimulus (which in turn is to be expected to correlate with the levels of a hormone that is intricately involved in calming down inflammation).