Check out these studies on testosterone levels and strength training:

Scand J Med Sci Sports. 2001 Dec;11(6):347-54.

The effect of short-term strength training on human skeletal muscle: the importance of physiologically elevated hormone levels.

Hansen S, Kvorning T, Kjaer M, Sjøgaard G.

Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense University.
Abstract

The effect of strength training and endogenously elevated hormone levels (plasma testosterone, growth hormone (GH) and cortisol) was studied in 16 young untrained males, divided into an arm only training group, A, and a leg plus arm training group, LA, in order to increase circulating levels of anabolic hormones. Both groups performed the same one-sided arm training for 9 weeks, twice a week. Group A trained only one arm (AT), the contralateral arm serving as control (AC), whereas group LA additionally trained their legs following the training of the one arm (LAT), with the contralateral arm serving as control (LAC). In spite of the attempt to match the two groups, the initial isometric arm strength was 20-25% lower for group LA compared to group A (significant for the arm to be trained). Isometric strength increased significantly in LAT and LAC by 37% and 10%, respectively, while the 9% and 2% increases in AT and AC, respectively, remained insignificant. Isokinetic strength increased at one out of three velocities tested for the trained arm relative to the untrained arm in both group A and group LA (P<0.05). Functional strength increased significantly by 20% in LAT, 18% in LAC, 19% in AT, and 17% in AC. Hormonal responses were monitored during the first and last training sessions. Resting hormone levels remained unchanged for both groups. However, during the first training session plasma testosterone as well as plasma cortisol increased significantly in group LA but not in group A. Plasma GH rose in all exercise tests, except during the last test in group LA, but was significantly higher in group LA than in group A in the first training session. In conclusion, a larger relative increase in isometric strength was found in the group having the highest hormonal response. However, due to the initial difference in isometric strength caution must be taken with the interpretation of this finding, which may only indicate a possible link between anabolic hormones and muscle strength with training.

PMID: 11782267 [PubMed - indexed for MEDLINE]

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Journal of Applied Physiology
Vol. 82, No. 1, pp. 49-54, January 1997
EXERCISE AND MUSCLE

Testosterone and cortisol in relationship to dietary nutrients and resistance exercise

Volek, Jeff S., William J. Kraemer, Jill A. Bush, Thomas Incledon, and Mark Boetes.

Testosterone and cortisol in relationship to dietary nutrients and resistance exercise. J. Appl. Physiol. 82(1): 49-54, 1997.---Manipulation of resistance exercise variables (i.e., intensity, volume, and rest periods) affects the endocrine response to exercise; however, the influence of dietary nutrients on basal and exercise-induced concentrations of hormones is less understood. The present study examined the relationship between dietary nutrients and resting and exercise-induced blood concentrations of testosterone (T) and cortisol (C). Twelve men performed a bench press exercise protocol (5 sets to failure using a 10-repetitions maximum load) and a jump squat protocol (5 sets of 10 repetitions using 30% of each subject's 1-repetition maximum squat) with 2 min of rest between all sets. A blood sample was obtained at preexercise and 5 min postexercise for determination of serum T and C. Subjects also completed detailed dietary food records for a total of 17 days. There was a significant (P <= 0.05) increase in postexercise T compared with preexercise values for both the bench press (7.4%) and jump squat (15.1%) protocols; however, C was not significantly different from preexercise concentrations. Significant correlations were observed between preexercise T and percent energy protein (r = -0.71), percent energy fat (r = 0.72), saturated fatty acids (g · 1,000 kcal-1 · day-1; r = 0.77), monounsaturated fatty acids (g · 1,000 kcal-1 · day-1; r = 0.79), the polyunsaturated fat-to-saturated fat ratio (r = -0.63), and the protein-to-carbohydrate ratio (r = -0.59). There were no significant correlations observed between any nutritional variables and preexercise C or the absolute increase in T and C after exercise. These data confirm that high-intensity resistance exercise results in elevated postexercise T concentrations. A more impressive finding was that dietary nutrients may be capable of modulating resting concentrations of T. nutrition; carbohydrate; fat; protein; steroid hormones

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Journal of Applied Physiology, Vol 69, Issue 4 1442-1450, Copyright © 1990 by American Physiological Society

Hormonal and growth factor responses to heavy resistance exercise protocols

W. J. Kraemer, L. Marchitelli, S. E. Gordon, E. Harman, J. E. Dziados, R. Mello, P. Frykman, D. McCurry and S. J. Fleck

Exercise Physiology Division, US Army Research Institute of Environmental, Natick, Massachusetts 01760-5007.

To examine endogenous anabolic hormone and growth factor responses to various heavy resistance exercise protocols (HREPs), nine male subjects performed each of six randomly assigned HREPs, which consisted of identically ordered exercises carefully designed to control for load [5 vs. 10 repetitions maximum (RM)], rest period length (1 vs. 3 min), and total work effects. Serum human growth hormone (hGH), testosterone (T), somatomedin-C (SM-C), glucose, and whole blood lactate (HLa) concentrations were determined preexercise, midexercise (i.e., after 4 of 8 exercises), and at 0, 5, 15, 30, 60, 90, and 120 min postexercise. All HREPs produced significant (P less than 0.05) temporal increases in serum T concentrations, although the magnitude and time point of occurrence above resting values varied across HREPs. No differences were observed for T when integrated areas under the curve (AUCs) were compared. Although not all HREPs produced increases in serum hGH, the highest responses were observed consequent to the H10/1 exercise protocol (high total work, 1 min rest, 10-RM load) for both temporal and time integrated (AUC) responses. The pattern of SM-C increases varied among HREPs and did not consistently follow hGH changes. Whereas temporal changes were observed, no integrated time (AUC) differences between exercise protocols occurred. These data indicate that the release patterns (temporal or time integrated) observed are complex functions of the type of HREPs utilized and the physiological mechanisms involved with determining peripheral circulatory concentrations (e.g., clearance rates, transport, receptor binding). All HREPs may not affect muscle and connective tissue growth in the same manner because of possible differences in hormonal and growth factor release.

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Eur J Appl Physiol. 2000 May;82(1-2):121-8.

Hormonal responses to high- and moderate-intensity strength exercise.

The hormonal responses of nine male, strength athletes to strength exercise were examined. The athletes performed one moderate- and one high-intensity strength exercise workout. In the high-intensity workout, the load was 100% of each subject's three-repetition maximum (3-RM) for squats and front squats, and 100% of each subject's six-repetition maximum (6-RM) for leg extensions. In the moderate-intensity workout, the load was 70% of the high-intensity protocol. Rest periods between sets were 4-6 min for both workouts. Blood samples were taken before, 30 min into, and every 15 min for the 1st h after exercise, and then 3, 7, 11, 22 and 33 h after exercise, thus allowing examination of both the acute and prolonged hormonal responses. Blood samples were analyzed for testosterone, luteinizing hormone (LH), follicle stimulating hormone (FSH), cortisol, adrenocorticotrophic hormone (ACTH), growth hormone (GH), insulin-like growth factor (IGF-1), insulin, sex hormone binding globulin, creatine kinase, total protein, glucose and lactate. The acute responses of testosterone and cortisol were greater during the high-intensity protocol as compared to the moderate-intensity protocol. The cortisol response was associated with an increase in ACTH concentration. LH and FSH showed no response to either protocol. Acute GH responses were not different between protocols. There were great inter-individual differences in acute GH responses to both protocols. There were no significant differences between protocols with regard to prolonged responses for any hormone. In both trials, IGF-1 concentrations were significantly lower at 0800 hours the morning after exercise as compared to concentrations found at 0800 hours the morning before exercise. The mechanisms responsible for reducing IGF-1 concentration in these trials are unclear, and it is not known if this reduction observed 22 hours after exercise is of physiological significance.

PMID: 10879453 [PubMed - indexed for MEDLINE]

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Endogenous anabolic hormonal and growth factor responses to heavy resistance exercise in males and females.

Int J Sports Med. 1991 Apr;12(2):228-35.

Kraemer WJ, Gordon SE, Fleck SJ, Marchitelli LJ, Mello R, Dziados JE, Friedl K, Harman E, Maresh C, Fry AC.

Exercise Physiology Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760-5007.
Abstract

To examine endogenous anabolic hormonal responses to two different types of heavy resistance exercise protocols (HREPs), eight male and eight female subjects performed two randomly assigned protocols (i.e. P-1 and P-2) on separate days. Each protocol consisted of eight identically ordered exercises carefully designed to control for load, rest period length, and total work (J) effects. P-1 utilized a 5 RM load, 3-min rest periods and had lower total work than P-2. P-2 utilized a 10 RM load, 1-min rest periods and had a higher total work than P-1. Whole blood lactate and serum glucose, human growth hormone (hGH), testosterone (T), and somatomedin-C [SM-C] (i.e. insulin-like growth factor 1, IGF-1) were determined pre-exercise, mid-exercise (i.e. after 4 of the 8 exercises), and at 0, 5, 15, 30, and 60 min post-exercise. Males demonstrated significant (p less than 0.05) increases above rest in serum T values, and all serum concentrations were greater than corresponding female values. Growth hormone increases in both males and females following the P-2 HREP were significantly greater at all time points than corresponding P-1 values. Females exhibited significantly higher pre-exercise hGH levels compared to males. The P-1 exercise protocol did not result in any hGH increases in females. SM-C demonstrated random significant increases above rest in both males and females in response to both HREPs.(ABSTRACT TRUNCATED AT 250 WORDS)

PMID: 1860749 [PubMed - indexed for MEDLINE]

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So basically doing the strength lifting, like SQUATS and dead-lifts which uses the majority of your muscles increases testosterone levels which will than increase muscle size and strength of other muscles too.

If you want to build big muscles with weights
don't look any further. Here we will show you
the smart way of building muscle, without drugs!

There a few keys to building big, strong, powerful
muscles that will turn heads, and increase your
performance in your sports or activities.

You must eat more than you burn off, you must
lift more weight, and you need to rest more.

Here we will cover the training methods to build
major muscles quickly, to blow away the competition
and surpass people who are currently bigger or
stronger than you.

The reason for this is that I will show you
techniques that most people don't do, because
they don't understand how muscles operate or
they get their information from steroid driven
bodybuilders who do a ton of sets and reps that
are not needed for the average no-steroid man.

First before we go into some techniques, you must
understand how muscle works. Muscles love to sleep.
if they could they would sleep 24/7. The only
way they get used is because YOU choose to use
them! So if you don't work out you muscles won't grow.

Also if you can't beat your last workout you
won't get bigger, so if you can't push the extra
rep or lift that extra 5lbs you will just stay
the same.

Ok so now here are a couple excellent weight training
techniques to build muscle, strength and power:

1. The King Set!
 

WARNING: Not for the faint of heart!

This is basically the exercise above the super-set.
So for this technique you want to pick 3 compound
exercises for each major/minor muscle group.

Then you aim for using a weight for 10 reps per exercise
back to back to back with 10 - 30 seconds rest max.
in between exercises, this is usually the time
it takes to get to the next workout station.

You will only need to do the king set ONCE per muscle group.
Then move onto the next muscle group. Do
a king set for every muscle group you want to work on for
the session at the gym but don't overtrain, 20 mins - 1 hour of weights
is ideal for recovery and rest and growth. This way you
will be more refreshed and leaving the gym with higher
energy than when you went in.

Record the exercises, reps, weight used, rest times too.
You goal is to fully rest for 2-3 days to fully recover and aim to beat
your current workout numbers, if you are too sore still,
don't workout on that muscle group. If you can beat your
numbers you will grow every time you come into the gym,
for hard gainers, 2-4 times a week is enough and try to avoid no back
to back heavy lift days.

For example, let's say you wanted to workout on your
chest, the 3 exercises you could choice are flat bench press,
incline bench press, and standing cable flies. Don't be
afraid to be creative, and switch around the exercises, you
don't have to do the same ones each time either, maybe
you could add dumbbells presses, or push ups, or decline
bench presses.

NOTE: Your body will remember how to do everything you have
done in the last 6 months, but even better the last
3 months.

2. The Giant Set!
 

WARNING: May cause muscles to grow larger and turn heads in the gym..lol ;)

This method of weight training is excellent for
building raw power and strength, as well as build
your muscles thicker.

You will be using much more weight and resting much
more in between sets.

Like the King set, you only need to do one Giant set
per muscle group.

Pick ONE exercise per muscle group.

So again lets use the chest again for an example, let's say your
choice is the flat bench dumbbell press, after warming
up, pick a weight you can lift about 5 times, after
repping the weight for an all out effort of about 5 reps,
rest for about 30 seconds to a minute and then rep out
the same weight for as many more reps as you can, you
may be able to do another 4-5 or so then, you can stop
or you can rest another 30 to a minute and rep it out
again for as many reps as you can which may only be 2-4
Try not to go past 12-13 reps for the total reps of the
giant set. The goal will be to increase the weight or
decrease the rest time in-between sets

(Note: the dumbbell press is a safer choice when
lifting heavy weight, and the bench press
takes great technique to do really heavy and you better
have a spotter, also flat bench can cause other injuries
as well, like in your elbows and shoulders, or back)

With these two muscle building weight training techniques
you will be able to literally control how big and strong
you get as long as you are recording everything trying to beat your numbers and eating
properly and resting allot to recover fully between workouts so you can go all out each time.