The deadlift has the propensity to jump up really fast in terms of loading, then plateau and often regress after that. Why? Because the autonomic nervous system is highly affected by heavy pulls, so the sympathetic nervous system can become suppressed.
Avoiding the dreaded workout hangover from the deadlift is fairly simple: stay away from near maximal loading for long periods at a time. Actually focus on, you know, BUILDING deadlift strength and not just demonstrating it with 1RMs.
Don't Train the Deadlift "On the Nerve"
If you have to get psyched up for your top set of pulls then you're probably going to see this pattern of progression then regression: it goes up, it stalls, it regresses.
From an intensity/loading standpoint, the majority of your deadlift training should be done at loads of less than 85% of your 1 rep max. Trust me, you can build an impressive deadlift using sub-maximal loading while focusing on being explosive.
If you're adhering to not training on the nerve and being smart with your loading, then the other factor can be that the erectors (erector spinae muscles running the length of your back) are simply not recovering.
This can happen with those who like to squat one day during the training week, then deadlift on another day. Oftentimes they'll include direct low-back work like hypers or barbell rows where the lumbar has to do a lot of work in the static position.
All of this low-back work on top of the squats and deadlifts can create a high degree of fatigue in the erectors that'll suppress performance.
The solution to avoiding localized muscle fatigue in the erectors is to deadlift after your squats, and to switch over to chest-supported rowing variations. Deadlifting after squats isn't going to run you into the ground if you're smart with the loading, and the squats before the pulls actually serve as a great warm-up, eliminating the need for extended warm-ups for deadlifting.
Here's how I always worked this:
- Pause Squat
- Good Morning / Deficit Stiff Leg / Leg Press (usually there was a rotation here)
Day 2, later in the week
- Chest Supported T-Bar Row
- Lat Pulldown
- Leg Curl
- Leg Extension