Acute effects of a cluster-set protocol on hormonal, metabolic and performance measures in resistance-trained males

Abstract

Limited research exists on rest-pause or cluster-set (CS) protocols. Acute effects of a traditional set (TS) and CS protocols of resistance exercise on serum growth hormone (GH), cortisol (C), blood lactate (BL), countermovement vertical jump (CMVJ) and standing long jump (SLJ) were compared. Eleven resistance-trained males (22.9 ± 2.6 year; 176.9 ± 10.6 cm; 78.5 ± 1.6 kg; 12.9 ± 3.1% BF) completed one repetition maximum tests for clean pull (CP), back squat (BS) and bench press (BP). Subjects were then randomly assigned to TS or CS protocols for sessions 2 and 3, and performed CP and BS lifts followed by two circuits of three sets of three exercises. GH, C, BL, CMVJ and SLJ were measured pre-exercise (Pre), mid-exercise following completion of CS or TS protocol (Mid), immediately (IP), 15 (15P) and 30 (30P) minutes post-exercise. Repeated measures ANOVAs examined differences in GH, C, BL, CMVJ and SLJ. No differences (p>0.05) existed between protocols for GH and C. GH levels 15P were elevated (p<0.05) above 30P (15.78 + 4.66 vs. 12.10 + 4.66 µg·L(-1)). C levels 30P were elevated (p<0.05) above Pre (716.85 + 102.56 vs. 524.79 + 75.79 nmol·L(-1)). Interaction (p <0.05) existed between protocol and time for BL; mid-BL was lower for CS than TS (7.69 ± 3.73 vs. 12.78 ± 1.90 mmol·L(-1)). Pooled data for CMVJ and SLJ were greater (p <0.05) across the CS protocol. The less metabolically taxing CS protocol resulted in better sustainability of jump measures.

Acute response to cluster sets in trained and untrained men

“…In the current study, cortisol increased in a linear fashion in the TRD condition, remaining elevated 30 min post-exercise, while a lesser slope of increase was observed in CLU achieving only one value (15 min) above baseline values. This is in disagreement with Girman et al (2014) in which the authors reported a similar cortisol response for both CLU and TRD conditions. The similar high lactate values and accompanying pattern of growth hormone observed immediate post-exercise in that study likely contributed to the divergent findings.…”

“…TUT was not controlled during the current study, but TUT in Set 4 was 2.43 ± 0.09 and 2.26 ± 0.09 s in the TRD and CLU condition, respectively. In the study conducted by Girman et al (2014), TUT was controlled in a 2-0-2 tempo, providing for more than 1.5 s longer TUT than that reported in the current study. Further studies are necessary to examine the potential differences in effect of TUT and lactate on the growth hormone response following exercise.…”

“…While significantly lower lactate values were observed immediately following CLU performance, higher lactate values than those reported herein were reported immediately following performance of a final circuit (14.6 ± 0.4 mmol l −1 , TRD; 14.3 ± 0.4 mmol l −1 , CLU), and these did not differ between conditions. Thus, the similar lactate values could have contributed to the similar growth hormone response; however, differences in TUT may, too, have influenced the results by Girman et al (2014). Growth hormone has been shown to be elevated to a greater degree following slow movement exercise compared to normal movement (Goto et al 2009).…”

“…Goto et al (2005) reported no elevation in growth hormone post-CLU; however, it is again likely the failure of that exercise program to induce significant elevations in blood lactate was responsible for the lack of response, as there appeared to be a similar pattern in the CLU condition although not statistically significant. On the contrary, Girman et al (Girman et al 2014) found no difference in growth hormone between CLU and TRD conditions in a group of trained males. In an effort to mimic a typical hypertrophy off-season training day, subjects in that study performed two exercises (clean pull and back squat) using TRD and CLU followed by two circuits in which the set and rep configurations did not differ between conditions.…”

“…CLU incorporate a short rest (typically 15-30 s) between individual repetitions (inter-repetition rest) or group of repetitions (intra-set rest) (Haff et al 2008). The ability to maintain greater mechanical power output is facilitated by the ability of the phosphagen and glycolytic energy systems to recover during the added rest periods as evidenced by studies demonstrating lower blood lactate concentrations (Girman et al 2014;Goto et al 2005) following CLU when compared to TRD configurations, as well as greater intramuscular adenosine triphosphate (ATP) and phosphocreatine (PCr) concentrations (Gorostiago 2012).…”