When taken to failure, continuous tension (no lockouts) with lighter weight can build muscle similarly to a heavier weight with a lockout.
METABOLIC STRESS TRAINING? IS IT BETTER FOR GAINING MUSCLE SUMMARY
- Metabolic Stress Training does not seem to increase hypertrophy greater than traditional exercise.
- Blood flow restriction (BFR) training and moderately heavy weight programs (>65% of a 1 RM) result in similar increases in muscle growth.
- When taken to failure, continuous tension (no lockouts) with lighter weight can build muscle similarly to a heavier weight with a lockout.
- Blood Flow Restriction training can be effective for increasing muscle growth.
- BFR training with taking off a cuff during rest resulted in similar increases in muscle growth as BFR being left on the entire time.
- BFR training to failure causes more muscle damage and inflammation than BFR stopping short of failure; however, muscle growth is the same.
MECHANICAL TENSION VS METABOLIC STRESS: HOW TO MAXIMIZE HYPERTROPHY
Being in the gym for two decades, I once heard a trainer who had many elite-level bodybuilders and would tell them to never lockout at the end of the repetition because it takes more metabolic stress each repetition results in more muscle growth. This is complete bullshit, but let me explain why this makes no sense. You will accumulate more fatigue and metabolic stress if you don’t “lockout” at the end of the repetition.
Let’s look at the research for muscle growth for studies that did not lockout at the end of a repetition. One study found that subjects who lifted a weight in 1 second and lowered it in 1 second with no pause (i.e., did not lockout) with a heavier weight (i.e.,~80% 1RM) training to complete failure had similar increases in muscle growth as those who exercised with a lighter weight (~50% 1RM) with a slow lifter speed and a 1-second pause (3 seconds concentric, 3 seconds eccentric, 1 second isometric) training to failure. Despite having similar increases in muscle hypertrophy, the group that eliminated the isometric contraction (i.e., no pause) had greater metabolic stress consisting of higher lactate and lower muscular oxygenation.
METABOLIC STRESS MUSCLE GROWTH TRAINING
Another study by the same research group had subjects train with either constant tension (i.e., no pausing at the end of a repetition) or a regular resistance exercise group. Both groups trained to failure with the same exercises: machine squat, chest press, lat pulldown, abdominal crunch, and back extension. The normal group performed each exercise with a full range of motion, using an 80–90% one-rep max load and a 1-second lifting, 1-second lowering, and 1-second pause phase. The constant-tension group avoided locking out the joints, so there was continuous tension. They used a 55–60% one-rep max load and a 3-second lifting and 3-second lowering phase; there was no pause phase. At the end of the study, both groups increased muscle mass similarly.
This suggests that whether you want to lock out at the end of a repetition or keep continuous tension with no lockouts can increase muscle growth if you train to failure.  One important note, the continuous tension group used much less weight (i.e., 55-60% of a 1RM) but still built the same amount of muscle as the heavier weight group (i.e., 80-90% of a 1RM). This points to the fact that using a lighter weight until muscular failure with no lockouts at the end of repetition can build similar muscle growth as a heavier weight with a lockout. This again points to using lighter weights for periods to give tendons and ligaments recuperation time from using heavier weights while not sacrificing muscle growth.
METABOLIC STRESS STUDIES FROM BLOOD FLOW RESTRICTION TRAINING
Blood flow restriction (BFR) utilizes a tourniquet or other compression device around a muscle to reduce blood flow and create metabolic stress. It has been suggested that more metabolic stress stimulates muscle growth. Does this mean you should start using BFR training to increase muscle size?
If you look at the research, BFR training and moderately heavy weight programs (>65% of a 1-RM) result in similar increases in muscle growth.  BFR training can be good for injured people or people in rehabilitation because it incorporates very light weights but increases muscle growth. Some studies have found heavy lifting to have a slight edge in increased muscle and strength compared to whole-body BFR training.  If you want to experiment with BFR training, it may be worth trying on stubborn body parts that you are having issues growing, such as the calves and arms.  It has been documented that blood flow restriction training can result in similar increases in muscle growth as a high-rep, light weight traditional resistance training program, despite a lower training volume. 
A 2021 study found that calf muscle thickness increased after blood flow restriction training in well-trained resistance exercise men, despite a lower training volume. In the study, resistance-trained men exercised with 4 sets at 30% 1-RM until failure with and without a BFR cuff placed below the knee. At the end of the study, the average number of repetitions completed per training session was higher in the no BFR group compared (i.e., 70 reps) to the BFR group (i.e., 52 reps). Despite the higher training volume, the traditional resistance training group had slightly less muscle growth (+1.94%) than the BFR group (3.29%).
METABOLIC STRESS MUSCLE GROWTH TECHNIQUES
You can mimic BFR training or metabolic stress training without occluding blood flow. Researchers had subjects do BFR training with leg extension (20% of a 1-RM) in which they occluded blood flow with a cuff, or they had subjects do a leg extension but held their legs in the extended position (isometric position) for 5 seconds and squeezed as hard as they could with 20% of a 1-RM. At the end of the study, both groups had similar increases in leg size.  BFR training induces metabolic stress and less muscle damage than traditional exercise. Still, it has been found to induce similar or slightly less muscle growth than traditional resistance exercise.