5/3/1 FSL vs BBB vs SSL: Choosing Your Supplemental Template

You’ve done your main work — the 5/3/1 sets with the AMRAP on top. Now what? The supplemental template you choose determines the character of the rest of your training session. It shapes how much volume you accumulate, how fatigued you get, and ultimately what adaptation you drive.

The three templates you’ll encounter most often in 5/3/1 are FSL (First Set Last), BBB (Boring But Big), and SSL (Second Set Last). Each has a specific purpose, a specific feel, and a specific place in your training year.

This guide breaks down all three so you can pick the right one — or know when to switch.

The Three Templates at a Glance

FSL: First Set Last

FSL means you go back to the weight of your first working set after completing your main 5/3/1 sets. On Week 1 (5s week), your first working set is at 65% of your training max. So you’d do 5 sets of 5 at 65%.

Why FSL works

FSL is the lowest-fatigue supplemental option. The weight is light enough that form stays clean, bar speed stays high, and you accumulate meaningful volume without digging into your recovery. This makes it the default recommendation for:

• Beginners learning the 5/3/1 system
• Older lifters managing recovery
• Anyone running 5/3/1 alongside a sport where gym fatigue can’t interfere with practice
• Lifters refining technique on a main lift

FSL is also Wendler’s recommended starting point in 5/3/1 Forever. If you’re new to the program, start here. Run it for 2-3 cycles. Get the rhythm of the program down before adding intensity.

FSL variations

The standard is 5x5, but FSL has several variations:

• FSL 5x5 — the default, great balance of volume and recovery
• FSL 3x5 — reduced volume for high-stress periods
• FSL AMRAP — a single set at FSL weight for max reps (typically 15-20); a solid conditioning finisher
• FSL Widowmakers — one set of 20 reps at FSL weight; brutal but effective for hypertrophy

Progressing with FSL

FSL weight increases automatically as your training max goes up each cycle. Beyond that, you can progress by:

1. Reducing rest times between sets
2. Moving from 3x5 to 5x5
3. Adding the AMRAP or Widowmaker variation
4. Eventually graduating to SSL or BBB

BBB: Boring But Big

BBB is the most popular 5/3/1 supplemental template, and it earns its name. After your main 5/3/1 sets, you do 5 sets of 10 reps at a lower percentage — typically 50-60% of your training max.

Fifty reps of squats. Fifty reps of bench. Every session. It’s boring, and the sets are big.

For a deep dive, see our complete BBB guide.

Why BBB works

The mechanism is simple: volume drives hypertrophy. Five sets of ten at moderate weight accumulates substantial training volume in the muscles you’re targeting. Over months, this builds the muscle mass that supports heavier lifting.

BBB is best for:

• Lifters who want to get bigger — BBB is a hypertrophy program disguised as a strength program
• Intermediate lifters with solid technique who can handle the volume
• Off-season athletes focused on building a base

BBB intensity progressions

Wendler has laid out several BBB challenges that increase intensity over a cycle:

• Standard BBB: 5x10 at 50% for the entire cycle
• BBB 3-month challenge: 50% → 60% → 70% across three cycles
• BBB Beefcake: 5x10 at FSL weight (much harder — not for beginners)

The key with BBB is managing accessories. Because the supplemental volume is already high, accessory work should be minimal — 25-50 total reps of push, pull, and single-leg/core work. Don’t pile more volume on top of 50 reps of a compound lift.

When BBB goes wrong

BBB breaks lifters who treat 50% as easy and chase higher percentages too fast. Five sets of ten at 70% of your TM — especially on squats or deadlifts — is genuinely crushing. Start conservative. If the last set of ten is a grind, the weight is too heavy.

SSL: Second Set Last

SSL uses the weight of your second working set — the middle set. On Week 1, that’s 75% of your training max. On Week 3 (5/3/1 week), it’s 85%. You do 5 sets of 5 at that weight.

This is meaningfully harder than FSL. On 5/3/1 week, you’re doing 5x5 at 85% of your TM after already hitting your AMRAP at 95%. That’s real weight for real sets.

Why SSL works

SSL sits in the sweet spot between volume and intensity. The weight is heavy enough to drive strength adaptations directly — not just through the hypertrophy pathway like BBB. This makes SSL the choice for:

• Intermediate-to-advanced lifters whose strength responds more to intensity than volume
• Lifters focused purely on getting stronger without necessarily getting bigger
• Anyone who has outgrown FSL but doesn’t respond well to high-rep work

SSL demands respect

SSL is the most fatiguing of the three standard templates. On Week 3, you’re handling 85% of your TM for 25 reps across 5 sets — after already doing your top set. This requires:

• A properly set training max — if your TM is too high, SSL becomes impossible to recover from
• Adequate sleep and nutrition
• Honest autoregulation — if you can’t complete the sets with good form, the weight needs to come down
• A real deload every 2-3 cycles, not optional

SSL variations

• SSL 5x5 — the standard
• SSL 5x3 — reduced reps for even higher-intensity focus
• SSL 3x5 — reduced sets for recovery-limited lifters

Choosing Your Template

The right template depends on where you are and what you need. Here’s a decision framework:

Choose FSL if:

• You’re new to 5/3/1 (first 2-3 cycles)
• You’re recovering from injury or illness
• You’re in-season for a sport
• You want to prioritize AMRAP performance on the top set
• You’re over 40 and recovery isn’t what it used to be

Choose BBB if:

• You want to gain muscle mass
• You’ve run FSL for at least 2 cycles
• You can handle high-volume training (good sleep, good nutrition)
• You’re in an off-season or growth phase
• You don’t mind workouts lasting 60-75 minutes

Choose SSL if:

• You’ve been running 5/3/1 for 6+ months
• Your primary goal is strength, not size
• You respond better to heavier weights than high reps
• You’re willing to manage fatigue carefully
• Your training max is dialed in accurately

Switching Between Templates

Periodizing your supplemental work across the training year is one of the most effective strategies in 5/3/1. A common approach:

1. 2 cycles of FSL — build a base, dial in technique
2. 2-3 cycles of BBB — accumulate muscle mass
3. 2 cycles of SSL — realize that muscle mass as strength
4. 1 cycle of FSL or deload — recover and reset

This isn’t a rigid prescription. Listen to your body, track your AMRAP performance and estimated 1RM trends, and switch when the current template stops producing results or starts producing too much fatigue.

Deload Considerations

Each template has different deload needs:

• FSL: Deload every 3rd cycle (two cycles on, one deload)
• BBB: Deload every 2nd or 3rd cycle depending on intensity — BBB at 70% may need deloads every other cycle
• SSL: Deload every 2nd cycle — the accumulated fatigue from heavy supplemental work is real

During the deload, drop supplemental volume to 3x5 at FSL weights regardless of which template you’re running. The point is recovery, not stimulus.

Let the Program Do the Work

The beauty of 5/3/1’s supplemental templates is that they give you clear, structured options instead of leaving you to guess. Pick one, run it for at least two full cycles, track your progress, and let the data tell you when to switch.

Train531 lets you select your supplemental template and adjusts your workout programming automatically — including the progression, the percentages, and the deload timing. One less thing to think about so you can focus on the lifting.