If This Is Your First Week
Welcome. The first week of any training block is about finding your weights, not testing your limits. Every exercise will be new or have a new rep range, tempo, or variation. Take your time. It’s better to finish Week 1 feeling like you went a little too light than to start too heavy and have to drop weight mid-set.
By Week 2, you’ll know your numbers for every exercise and can start pushing harder.
If you’re on the FLEX Dumbbell track, everything in this guide applies the same way. Where we mention a barbell, just think of it as your dumbbells. The principles don’t change.
How Sets Work in FLEX
Each workout tells you exactly how many sets to do. These are your “working sets,” which just means your challenging sets where you’re lifting at the intended effort level. They don’t include any warm-up sets you do before them.
Before your first working set of any major exercise, always do 2-4 lighter warm-up sets. Start with an empty barbell (or the lightest dumbbells available) and add weight gradually until you’re close to your planned working weight. Your Prep Work warms up your whole body, but you still need these exercise-specific warm-up sets to prepare for heavier loads.
Each exercise in the app comes with a video demonstration and coaching notes. If you’re unsure how a movement should look or feel, check those before you start.
Choosing Your Weight: The RIR System
RIR means “Reps in Reserve.” It’s how many more reps you could have done if you kept going. For most performance work, aim for 2-3 RIR. This means you finish each set feeling like you could do 2-3 more reps with good form, but those extra reps would be very hard.
We use RIR instead of percentages (like “80% of your max”) because RIR adjusts to how you feel each day. On a good day you’ll naturally use heavier weight. On a tough day you’ll use lighter weight. Either way, you get the right training effect because the effort level stays the same.
Your First Set of Any Exercise
If you already have a sense of what you can lift for a given movement, start about 10-15% lighter than that. If you’ve never done the exercise before or you’re not sure where to start, pick a weight that feels comfortable and manageable. You can always go up.
After your first working set, check how it felt:
- You could have done 5 or more extra reps → go heavier next set
- You barely finished the minimum reps → go lighter next set
- You had about 2-3 reps left in the tank → perfect, stay there
This “check and adjust” process is how you find the right weight. It’s completely normal to adjust between your first and second set, especially in the first few weeks of a new block.
Example
Your workout says: 5 Sets of BB Front Squat, 3-second lowering phase
- Warm-up: empty bar for 8 reps, add some weight for 6 reps, add more for 4 reps
- Set 1: Pick a weight you think you can handle for all the reps with the slow lowering phase. Complete your reps. Check: could you have done 2-3 more? If yes, good weight. If you had 5 or more left, go up. If you barely made it, go down.
- Sets 2-5: Stay at the same weight if you’re still hitting your reps with 2-3 left in reserve.
Should I Use the Same Weight Every Set?
Generally yes. If you picked the right weight, you should be able to use it across all your working sets. If your last set drops below the prescribed reps, the weight was slightly too heavy. Make a note and adjust next session.
Some exercises have specific loading instructions built into the workout (for example, wave loading where the reps change but the weight stays the same, or a pyramid where reps decrease each set). When your workout includes specific loading instructions, follow those instead of this general guideline.
Progression Through a 6-Week Block
Each training block in FLEX runs for 6 weeks. Here’s how your effort should gradually build:
- Weeks 1-2: Keep 2-3 reps in reserve on every set. Focus on learning the movements and finding your weights. There is no rush. This is your foundation.
- Weeks 3-4: Start pushing a little harder. On your last set of the main exercises, you can go to 1-2 reps in reserve.
- Weeks 5-6: On your final 1-2 sets of the main lifts, push to 0-1 reps in reserve. This is where you test what you’ve built over the block.
When the Workout Uses Special Techniques
Some workouts include techniques that make the exercise harder than regular reps. For example:
- Tempo work (a “3-second lowering phase” means you lower the weight slowly over 3 seconds)
- Pauses (holding at the bottom of a squat for 2 seconds before standing up)
- AMRAP sets (doing as many reps as possible in a set time window on your final set)
When you see these, use lighter weight than you normally would. A 3-second lowering phase on a squat makes each rep significantly harder than a regular speed rep at the same weight.
Adjusting Day to Day
Your strength changes based on sleep, stress, and recovery. This is normal and expected. On days you feel strong, work toward the higher end of the rep range. On days you feel off, stay at the lower end and focus on movement quality.
The RIR system handles this automatically. As long as you finish each set with about 2-3 reps in reserve, you’re getting the right training effect regardless of what the number on the bar or dumbbell says. A “bad” day at lighter weight with proper effort is just as productive as a “good” day at heavier weight.
Common Questions
I finished all my reps but it felt too easy. Go heavier next set. If you consistently have 4-5 reps left in reserve, you’re not getting enough out of the exercise.
I couldn’t finish all the reps. Drop the weight 5-10% and finish your remaining sets. This is completely normal, especially in the first few weeks. Getting the full number of sets at the right effort matters more than the number on the bar.
I don’t know my starting weights for a new block. Start with a weight you’re confident you can handle for the top of the rep range. If your workout says 6-8 reps, pick a weight you can definitely do for 8. You can always go up. You can’t undo a set that was too heavy.
The workout says a specific tempo or technique I don’t understand. Check the coaching notes and video demo attached to the exercise in the app. If you’re still unsure, post in the community group. The coaching team and other members are happy to help.
I train with dumbbells only. Does all of this still apply? Yes. Everything in this guide works the same for the Dumbbell track. The only difference is the equipment. The principles of RIR, weight selection, and progression are identical.
