Friday, August 5, 2016

Building Extra-Strength With Cluster Training (6x1 With 25s Rest) - Works, but Classic Strength Training is also Effective

Cluster training is something most of you will be familiar with. To do it back squats, instead of curls or bench presses, however, is something you don't see very often in the gym, these days - rightly so?
If you want to build muscle strength or size, muscle contractions are obligatory. If that should necessarily be done at high intensities and until failure is still a much debated topic - just as debated as the link between strength and size gains.

Cluster training (CL) is a way of training that's supposedly helpful in building strength and hypertrophy. How effective it actually is, however, has rarely been studies in detail... until scientists from the Carnegie School of Sport at the Leeds Beckett University compared the acute (metabolic and mechanical) and chronic responses to classic strength (STR), hypertrophy (HYP), and two novel cluster training CL regimens involving the back-squat exercise.
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As Nicholson et al. point out, "[t]his approach was intended to answer key questions regarding the magnitude and type (i.e. neural) of adaptations resulting from workouts which set out to empha sise contrasting mechanical and metabolic responses" (Nicholson. 2016). The authors hypothesised that the CL regimens would "optimise the acute kinematic and kinetic responses with an attenuated metabolic response and that a CL regimen which permits a higher load would result in the largest increases in strength and muscle activity" (Nicholson. 2016).
"The actual study consisted of two separate investigations. Forty-six male subjects (age: 21.76 ± 2.60 years; height: 178.0 ± 6.3 cm; body mass: 81.14 ± 8.83 kg; 1RM: body mass ratio: 1.6 ± 0.3) volunteered to participate in both parts of the study. The subjects were chosen due to their experience in structured strength training (minimum 12 months) and their profciency in the back-squat exercise. During familiarisation, if subjects were unable to complete multiple repetitions (>8) of the parallel back squat with a weight equal to their own body mass on the bar they were excluded from the study. All subjects were not taking medication or any other nutritional supplements (e.g. creatine) known to affect energy metabolism or physical performance. The Faculty’s Research Ethics Committee approved the details of the study and all subjects gave written informed consent to indicate their voluntary participation" (Nicholson. 2016)
The actual study began with after the familiarisation with a standardised two-week pre-conditioning period, where subjects were matched according to 1RM strength in the back-squat exercise.
How does cluster training work? Well, the idea is that the resting 10-30s after each rep will improve the quality of performance during each of the repetitions - thus performing each and every repetition with a higher power output, peak barbell velocity, and peak barbell displacement, athletes are expected to be able to make the most of each rep and thus their workouts.

As Lawton et al. (2006) suggest that the inclusion of a cluster set–loading paradigm may be most beneficial for explosive or ballistic strength training methods such as those used in programs that rely on weightlifting movements. In their 2008 review Haff et al. write that this idea is supported - at least partly - by studies from Rooney et al. (1994); They do yet also acknowledge that Kraemer et al. (1996) "suggest that lactate production favors a hypertrophic response" (Haff. 2008).
Subjects were subsequently assigned to either a strength- (STR; n = 11) or hypertrophy-type (HYP; n = 12) regimen, a cluster-type (CL) regimen involving greater total resting time (CL-1; n = 12) or a CL regimen involving greater total rest and volume load (CL-2; n = 11).
Figure 1: Schematic representation of the experimental groups and design. 6/1 denotes six single reps (Nicholson. 2016)
The primary investigation then examined the chronic effects of these back-squat workouts performed twice weekly for a 6-week period. Specifically, subjects were tested for dynamic, isometric and isokinetic strength, sEMG activity and power performance during 1 testing session at pre-, mid- and post-training (see details in Figure 1).
Figure 2: Changes in 1RM back squat strength during and following the training period (Nicholson. 2016).
The secondary investigation examined the acute effects of the experimental workouts on blood lactate (BL) concentration and repetition quality during one visit to the laboratory. Data from both investigation were analyzed and yielded both surprising and unsurprising results:
  • chronically - significant improvements in 1RM strength in the STR (12.09 ± 2.75 %; p < 0.05, d = 1.106) and CL-2 (13.20 ± 2.18 %; p < 0.001, d = 0.816) regimens compared to the HYP regimen (8.13 ± 2.54 %, d = 0.453)
  • acutely - greater time under tension (TUT) and impulse generation in individual repetitions with STR and CL-2 than with HYP workouts (p < 0.05), while STR (+3.65 ± 2.54 mmol/L−1) and HYP (+6.02 ± 2.97 mmol/ L−1) workouts resulted in significantly greater elevations in blood lactate concentration (p < 0.001) than the CL-1 and CL-2 workouts
What about the muscle gains? No, those were not assessed at any timepoint. Not exactly what you'd expect if you include a "hypertrophy" group, ... a pity, because one can only speculate whether either of the increased metabolic stress markers in the HYP regimen may be related to increased skeletal muscle hypertrophy.
Polarized training? What is it, how can you use it and why you even use it? Find out more...
What appears to be unquestionable is that the good old strength training regimen still is an effective means of building strength and power under the bar. On the other hand, Nicholson et al. (2016) were able to demonstrate that 25s of inter-set rests won't impair the strength response to back squats - specifically, if the extra rest is used to increase the load by another 10%.

This evident link between how much you weight you add to the bar today and how much you can add during your next workout is everything but news, though.

Unlike hypertrophy, i.e. the growth of skeletal muscle, maximal strength development appears to require maximal weights. In that, the small increase in volume load with CL-2 vs STR could be ascribed to the lack of difference in central mechanical variables such as the concentric time-under-tension, the average force production per lbm body weight, the impulse, velocity and power between the STR and CL-2 regimen | Comment!
  • Haff, G. Gregory, et al. "Cluster training: A novel method for introducing training program variation." Strength & Conditioning Journal 30.1 (2008): 67-76.
  • Kraemer, William J., Steven J. Fleck, and William J. Evans. "Strength and power training: physiological mechanisms of adaptation." Exercise and sport sciences reviews 24.1 (1996): 363-398.
  • Lawton, Trent W., John B. Cronin, and Rod P. Lindsell. "Effect of interrepetition rest intervals on weight training repetition power output." The Journal of Strength & Conditioning Research 20.1 (2006): 172-176.
  • Nicholson, G., T. Ispoglou, and A. Bissas. "The impact of repetition mechanics on the adaptations resulting from strength-, hypertrophy-and cluster-type resistance training." European Journal of Applied Physiology (2016): 1-14.
  • Rooney, KIERAN J., Robert D. Herbert, and Ronald J. Balnave. "Fatigue contributes to the strength training stimulus." Medicine and science in sports and exercise 26.9 (1994): 1160-1164.