This is probably best discussed in the American College of Sports Medicine's position stand (Progression Models in Resistance Training for Healthy Adults). You will be interested in the Muscular Hypertrophy section, which starts approximate one-third of the way through the position stand.

http://journals.lww.com/acsm-msse/Fulltext/2009/03000/Progression_Models_in_Resistance_Training_for.26.aspx

Check the paper "Strength and hypertrophy adaptations between low- versus high-load resistance training: A systematic review and meta-analysis" by Schoenfeld et al. 2017 published in the JSCR.

The results of most studies  concerning developing muscle hypertrophy favoured 90% intensity with lower volume and longer interval of rest for resistance training athletes. healthy young men who are not athletes however need to start progressively from a lower intensity through periodization to arrive at 90% intensity in order to prevent injury to the big muscles especially.

The effect of training volume and intensity on improvements in muscular strength and size in resistance-trained men by Gerald T. M.  et al 2015 in Physiological Reports

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4562558/

Olufunmilola Leah Dominic:

Not sure how did you come to that conclusion. I would say that the majority of your recommendations are not supported by the current body of evidence.

It has been shown that both resistance trained and untrained individuals can achieve robust muscle hypertrophy using a low-load, nonperiodized program. I would direct your attention to the recent paper mentioned above.

Thanks Olufunmilola Leah Dominic, this paper is new for me, I'll read it ASAP. I already knew the others.Thanks guys!

90%

Dear Lenoid the only intensity of 90% do not provide you 100% hypertrophy. A lots of variables to consider.

Dear Antonino,

"the only intensity of 90% do not provide you 100% hypertrophy. A lots of variables to consider" - Yes, you are right. However, your question rings as: "...for a good muscle hypertrophy in young healthy males (70%-80%-90%?)". Like question, like answer.

Ah! You're right! You win...

A number of studies (ACSM, 2009; BAECHLE et al., 2008; BEHM, 1995; FIELDS et al. 2002) discuss the ideal percentage of 1RM for the promotion of hypertrophy. However, probably, due to differences in inter and intra-subjects, has not been possible to reach consensus on the matter. Anyway, the evidences suggests that the ideal loads for promotion of hypertrophy is in a range between 6 to15 voluntary maximum repetitions. Therefore, some time ago in our laboratory we chose to use periodizations with the maximum number of maximum repetitions-ranging from 6 to8 (heavy), 8-10 (moderate) and 10-12 (light), with greater emphasis to the 8-10 range. This way, we hope to cover all the possibilities of recommendation.

Amandio Geraldes

standard hypertrophy 70%-90% recommended which depends on variables

https://www.strengthandconditioningresearch.com/

Great Pic! Thanks to Suntharalingam Thanuraj

A lots of info are coming out from this generic and open question.

It is clear that training intensity is crucial, but also recovery and modality of execution are also determinant for ideal improvements.

2 seconds up and 4 seconds down is really different stimulus when compared with 1up/3down and so on. I mean concentric (up) and eccentric (down) phases...

yeah welcome that's right

For those wanting to improve their muscular endurance alongside muscle gains, it is traditionally recommended to use low to moderate intensity (50-75% 1RM - standing for 50 to 75 percent of your 1 rep max) with a very moderate volume (3-6 sets of 10-20 reps, with 8-12 reps being the hypertrophy range) (Charlebois, 2007 ...Apr 2, 2015)

The Schoenfeld et al. 2017 meta-analysis points out that heavy loading seems to be more interesting for hypertrophy. The studies of Campos et al., 2002 (experimental) and Fry et al., 2004 (review) have similar opinions. In my practical experience loads of 8-RM to 12-RM (75% to 85% of 1-RM) are the best for hypertrophy. However the interactions with the training volume, interval, periodization must be respected for the ideal physiological adaptation. Hormonal and inflammatory responses (arising from muscle damage) should be taken into account. One tip is that of Toigo et al., 2006, Spiering et al., 2008 and Ament & Verkerke, 2009.

Thanks Gilmar for this update!

Interesting Peter’s point of view.

Hi Antonino,

Some interesting responses, most of which are backed up by scientific rigour. I'd add that you would need to define 'young males' as depending on their age would impact the intensity as you would need to consider training age, prior experience, etc. Given the first 6-8 weeks (approximately) of resistance training gains are neural adaptations and not hypertrophy per say, you would need to consider additional factors rather than intensity.

Moreover, are we taking intensity via eccentric, concentric and/or isometric contractions? Each variable can be manipulated to further hypertrophy gains.

Like one of my peers previously posted, I'd refer to the ACSM guidelines for further guidance.

Stuart

Bachelor of Exercise and Sports Science and First Class Honours in biomechanics).

It is not only neural adaptations in first weeks. It is also restructering of muscle structures themselves. This goes hand in hand with more muscle protein synthesis. However, this is not hypertrophy. Of course some people have better structured muscle than others and get to hypertrophy rather quicker. The same with neural adaptations. In general though it takes some weeks. That is why I am against doing free weights in the initial weeks.

Normally eccentric should not be performed for beginners. There should be a normal pattern of 1-2 sec concentric. Maybe 1 sec hold isometric, and a controlled eccentric phase. The isometric can be negative because sometimes the end position is not most optimal for muscles. With a low row, the end position can have a small latissimus doris position and more impact on for instance the posterior deltoid.

ACSM is also sometimes to much average. There should be more elaborate guidelines and a combination of meta-analysis and inter-individual assessement by expert trainers.

I think that intensity is not the only factor. Surely, if you severely decrease your rest periods between sets (less than 30 seconds to increase metabolic pressure), then it's hard to increase your intensity. The general belief (at least in gym and IRAN) is that 60 to 80 % of the 1RM is appropriate, but this method often uses three-sets systems with 10-repetitions and one minute of rest. While there are dozens of different and affected systems now. I strongly recommend reading this book from Schoenfeld, Brad :

"Science and Development of Muscle Hypertrophy"

and this paper:

http://professoralexandrerocha.com.br/wp-content/uploads/2016/04/Effects-of-Low-Versus-High-Load-Resistance-Training-on-Muscle-Strength-and-Hypertrophy-in-Well-Trained-Men.pdf