Endocrine Response Patterns to Acute Unilateral and Bilateral Resistance Exercise in Men

Abstract

Rehabilitation programs and research experiments use single-arm protocols in which the contralateral arm is not functional or used as a control limb. This study was interested in determining the hormonal signal impacts of such one- versus two-arm exercise responses that might have an impact on adaptational changes with training. The purpose was to examine the acute hormonal responses to a unilateral and a bilateral upper-body resistance exercise (RE) protocol. A balanced randomized treatment intervention with series time frame for blood collections before and after exercise was used as the basic experimental design. Ten recreationally resistance trained men (18-25 years, 20.4 +/- 1.2 years, 175.6 +/- 4.5 cm, 81.7 +/- 9.3 kg) gave informed consent to participate in the investigation. Each subject performed unilateral (dominant arm only) and bilateral upper-body RE protocol separated by 1 week in a balanced randomized fashion. The RE protocol consisted of 3 sets of 10 repetitions of 5 different dumbbell upper-body exercises at 80% of 1-repetition maximum, and blood samples were obtained before and 5, 15, and 30 minutes immediately postexercise (IP). Blood was obtained and analyzed for lactate, immunoreactive growth hormone (iGH), cortisol (C), total testosterone (T), and insulin concentrations. Total volume of work also was determined for the 2 exercise sessions. Total volume of work performed during the unilateral protocol was 52.1% of that for the bilateral protocol. Both RE protocols elicited a significant (p < or = 0.05) increase in lactate and iGH, but the increase for the bilateral condition was significantly greater. Cortisol decreased significantly during recovery for the unilateral condition. Testosterone was not affected by either protocol. Insulin was significantly increased at IP and 5 minutes postexercise for both conditions.These results indicate that the hormonal responses to dominant-arm unilateral RE is blunted compared to that for bilateral RE. This differential endocrine response is likely a result of the difference in volume between the protocols. It is important to pay attention to the amount of muscle mass utilized in a resistance exercise protocol to optimize endocrine signaling.

Influence of upper-body exercise order on hormonal responses in trained men

“…In accordance with these previous findings, in our study, sequence A (which involved a 40% greater volume of work) promoted a significantly greater GH response than sequence B. The absolute GH responses, as well as the difference in responses between the 2 sequences, are similar to the GH responses found by Migiano et al (2010) for unilateral and bilateral (approximately twice the work as unilateral) upper--body resistance exercise. The effect of total volume of work on GH secretion from the anterior pituitary is in large part due to the metabolic demand caused by the volume during the exercise session; this metabolic demand is generally reflected by the lactic acid response pattern (Kraemer et al 1990;Smilios et al 2003;Migiano et al 2010).…”

“…Because the load was constant for all sets of a particular exercise, the volume completed (load × repetitions) was solely dependent on the total repetitions completed; thus, the total repetitions and volume were greater when the larger muscle--group exercises were performed first (sequence A). It is well established that the total volume of work completed during a resistance exercise session influences the magnitude of the hormonal response, especially that of GH (Hansen et al 2001;Migiano et al 2010;Kraemer et al 1990;Leite et al 2011;Smilios et al 2003). In accordance with these previous findings, in our study, sequence A (which involved a 40% greater volume of work) promoted a significantly greater GH response than sequence B.…”

“…The absolute GH responses, as well as the difference in responses between the 2 sequences, are similar to the GH responses found by Migiano et al (2010) for unilateral and bilateral (approximately twice the work as unilateral) upper--body resistance exercise. The effect of total volume of work on GH secretion from the anterior pituitary is in large part due to the metabolic demand caused by the volume during the exercise session; this metabolic demand is generally reflected by the lactic acid response pattern (Kraemer et al 1990;Smilios et al 2003;Migiano et al 2010). The drop in blood pH that is concurrent with a large increase in blood lactate concentration during exercise can increase GH secretion; conversely, infusion of the pH buffer sodium bicarbonate (NaHCO3) results in a reduction in GH both at rest and after exercise (Elias et al 1997).…”

“…In contrast, Migiano et al (2010) found that neither unilateral nor bilateral (twice the volume) upper--body dumbbell exercises resulted in an exercise--induced increase in TT, despite a similar repetition and load range (4 sets of 10 repetitions at 80% of 1--RM for 5 exercises). Our data confirm the literature (Migiano et al 2010) demonstrating that the involvement of only the upper--body musculature in trained men appears to be insufficient to induce significant increases in FT or TT. An exercise--order effect for testosterone is, therefore, not likely to exist for upper--body resistance--exercise sessions in trained men.…”

“…Resistance--exercise protocols are often structured to concentrate on upper--and lower--body muscle groups in separate sessions, and often on separate days; this is particularly true for hypertrophy--oriented protocols practiced by bodybuilders, rehabilitation sessions during physical therapy, and for individuals who have only upper--body capabilities. The hormonal response to an upper--body resistance session in men is generally much less than that from a lower--body exercise session, but the response is affected by the volume of the session (Migiano et al 2010). Because the potential for acute hormonal responses is correspondingly less, the order of exercises for an upper--body session might be especially important for creating the most effective anabolic stimulus for that session.…”