You Need to Be Unbalanced & Eccentric

In order to have a really good, PROGRESSIVE workout program, you need to shake things up atl LEAST every 4-6 weeks. Your body adapts and plateaus within that time frame.

Some trainers recommend a unique program EVERY workout, but that's counterproductive for 99% of the general public. If you're an outlier like I train, then that might be feasible under special cicumstances.Anyway, that's another post.You can still raise the intensity of each exercise within a workout program.
There are many ways of increasing your workout intensity, and here I will focus on  two methods:

 
BE UNBALANCED:

Stability is a "state" that's constantly in flux based on the positioning of your center of mass (or gravity) within your base of support.

Balance, on the other hand, is ability - something that can be trained. Your stability changes transiently when you reposition yourself (e.g., squat lower) or enter a different environment (e.g., stand on ice.) Your balance changes only chronically when you improve (or decrease) strength, kinesthetic awareness, coordination, or proprioception.

An exercise with a wide base of support will always be easier to accomplish than one with a narrow base of support. A simple example of this is a bilateral squat (the wide base is the distance between the two feet) as compared to a single-leg squat (narrow base: the surface area of just one foot).

BE ECCENTRIC:

The "eccentric" part of a motion is where the muscle length is increased. The "downward" phase of a dumbbell or leg curl "lengthens" the biceps and hamstrings group, respectively. Slowing down your tempo to increase the eccentric portion of the lift increases its intensity ( and is the part that will really make you sore!)

 As my friend at Testosterone Nation wrote: "Decelerative movements like forward lunges and lateral lunges are much more unstable and challenging than predominantly accelerative exercises like reverse lunges and step-ups.

 If you wanted to look at it as somewhat of a continuum, here's what you'd have (from accelerative on the left to decelerative on the right):

Sled Push/Drag →Step-up → Reverse Lunge → Slideboard Reverse Lunge → Forward Lunge

There's really no eccentric stress on a sled push/drag — which is why it really won't make you sore . Step-ups have slightly more eccentric stress, but less than reverse lunges. Add a slideboard to those reverse lunges, though, and the lifter has to work harder to control the exaggerated eccentric component."

So, consult with your highly-trained fitness consultant and get to work. It takes time to GET CRAZY FIT!