Periodization in training: does the plan matter?

The short answer

• 35

  Studies in a 2022 review. Planned changes gave a small strength boost but no extra muscle

• 29

  Studies in a 2026 review. Linear and undulating plans built strength about equally

• ≈20kg

  Squat gain in 8 weeks, whether lifters added reps or added weight

• 4–6wk

  Usual gap between easier weeks in coaching practice

Key findingAny sensible plan that slowly asks more of you will work. The style of periodization is a detail. It may help strength a little in experienced lifters, but it doesn’t add muscle.

What is periodization in training?

Periodization means planning changes to your training over weeks or months. You might change how heavy the weights are, how many reps you do or how many sets. The aim is to keep making progress and to manage tiredness.

A plan that stays the same on purpose is called non-periodized. You do the same sets and reps each time and add weight as you get stronger. That is still progress. It just isn’t planned in phases.

The 2026 guideline from the American College of Sports Medicine (ACSM) describes three common styles:

• Linear periodization. The weights get heavier and the reps fewer as the weeks go by.
• Undulating periodization. The reps and weights change from day to day or week to week. Daily undulating periodization (DUP) might mean a heavy day, a medium day and a light day in one week.
• Block periodization. Training is split into blocks of a few weeks, each with one main goal.

Does periodization beat a plan that stays the same?

A 2022 review tested this. It pooled the results of 35 earlier studies. In every study, both groups did the same total amount of training, so only the plan was different.

Planned changes gave a small extra gain in one-rep max. That is the most weight you can lift once with good form. Muscle growth was the same either way.

Look at the trained lifters. For them, undulating plans beat linear plans for strength. In beginners, there was no difference. The authors suggest the extra strength may come from the nerves getting better at heavy lifts, not from more muscle.

The 2026 ACSM guideline looked at 137 reviews. It found that periodization didn’t change muscle growth, and that its effect on strength was unclear. The guideline says periodization matters less than experts used to think.

Linear or undulating periodization: which is better?

A newer review from 2026 compared linear and undulating plans head to head. It pooled 29 studies with 704 people aged 14 to 80.

Strength gains were about the same. That held for upper-body pushing in 23 studies and for the squat in 25 studies. It held for beginners and for trained lifters.

So the two reviews don’t fully agree about trained lifters. The newer one is bigger, and it found no difference. If undulating plans do help experienced lifters, the gain is small.

Block periodization has less research. The National Strength and Conditioning Association (NSCA) describes a 22-week trial in adults in their early 70s. It compared no periodization, block periodization and daily undulating periodization. All three helped, with no differences between them.

Should you add reps or add weight?

Progressive overload means making training a bit harder over time. You can add weight, or keep the same weight and add reps. Our progressive overload guide shows both, step by step. A 2022 trial compared them.

Researchers put 43 trained young adults into two groups by chance. One group added weight while staying at 8 to 12 reps. The other kept the same weight and added reps. Both did 4 sets of 4 leg exercises, twice a week, for 8 weeks.

Muscle grew about the same in both groups. Strength did too. On average, the weight group gained 21.8 kg on the squat and the reps group gained 19.3 kg. That gap was too small to be sure of.

Do you need a deload week?

A deload is a planned easier spell. In 2023, experienced coaches from several countries agreed on a definition. It is a period of lighter training to reduce tiredness, help recovery and get ready for the next block.

The coaches agreed you can deload by doing fewer sets, fewer reps or fewer sessions. A deload can be planned, or taken when you feel worn out. Earlier interviews found that coaches usually deload every 4 to 6 weeks, for about a week. For a sample week, see our deload week guide.

The first trial on deloads came out in 2024. Researchers put 50 trained young adults into two groups by chance, and 39 finished. Both groups did a hard 9-week leg programme. One group took week 5 completely off. The other trained straight through.

Muscle grew the same in both groups. Strength rose a bit less in the group that took a week off. The researchers put the chance that training straight through gave more strength at about 85% for the squat and 92% for the knee test. Many people said they felt sluggish after the break, not refreshed.

Keep two things in mind. The deload here was a full week off, not a lighter week. And almost nobody in the study felt they needed a break. So the trial doesn’t show that a lighter week is bad. It does suggest that a break you don’t need won’t bring extra gains.

Does exercise order matter?

A 2021 review of 11 studies asked whether to do big or small exercises first. Big, multi-joint lifts move several joints, like squats and presses. Small, single-joint lifts move one joint, like curls.

Strength grew most on the exercises that came first in the session. Muscle grew the same either way. The 2026 ACSM guideline agrees. Doing a lift early helped its strength but not muscle growth. So put the lift you most want to improve first.

Claims and evidence

• ClaimYou need a periodized plan to build muscle.

  EvidenceWhen total work was matched, planned changes didn’t add muscle in a review of 35 studies. The 2026 ACSM guideline found the same.

• ClaimUndulating periodization is always better than linear.

  EvidenceA 2022 review found a small strength edge for undulating plans, in trained lifters only. A bigger 2026 review of 29 studies found no clear difference.

• ClaimYou have to add weight every week to keep progressing.

  EvidenceIn an 8-week trial, adding reps built about as much muscle and strength as adding weight. Both groups gained about 20 kg on the squat.

• ClaimEveryone needs a deload every four weeks.

  EvidenceThere is just one trial. A full week off didn’t help muscle and slowed strength a little. Expert coaches favour lighter weeks, planned or taken when you feel worn out.

What this means for you

What the research can’t tell you yet

• Long-term results. Most studies lasted weeks or a few months, not years.
• Who was studied. Most people were young adults. The deload trial only included people aged 18 to 40.
• Small trials. The two trials here had about 20 people in each group, so small differences are hard to spot.
• Lighter deloads. The deload trial tested a full week off, not the lighter week most lifters use.

How Bodyvault uses this research

Bodyvault’s programme library includes plans built on linear progression, double progression, daily undulating and block periodization. Generated plans, part of Bodyvault Pro, run in blocks of 4 to 6 weeks. Weekly sets rise by about one per muscle, and the last week is a deload with about 45% fewer sets and easier effort. You can also turn a deload on early. Between sessions, Bodyvault suggests adding a rep until every set reaches the top of your rep range, then the smallest weight step. Its generated sessions put the big multi-joint lifts first.

General information about fitness and nutrition, not medical advice. If you have a health condition, are pregnant or take medication, talk to your doctor before changing your diet or training.