Fatigue in Lambert-Eaton Myasthenic Syndrome (LEMS): Pacing Your Way to a More Active Day

Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune condition that disrupts communication between nerves and muscles, leading to weakness and fatigue. In LEMS, the signal from the nerve doesn’t fully reach the muscle, which makes it harder for muscles to contract and sustain activity.

That breakdown in signaling is what drives fatigue in LEMS. The more you use your muscles, the harder they have to work — and the more quickly they tire.

Overexertion in people with LEMS can lead to a prolonged decrease in function rather than just temporary tiredness, says Georgette Dib, MD, a neurologist at Cleveland Clinic in Ohio.

“That’s why energy management is one of the most important long-term strategies,” says Dr. Dib. By pacing your activity, planning ahead, and building in rest, many people with LEMS can be more active while limiting fatigue.

Fatigue in LEMS is closely tied to how the condition affects muscle function, which in turn impacts weakness and energy level.

Muscle Weakness vs. General Exhaustion

Fatigue in LEMS can show up in different ways.

One is muscle weakness, which often begins in the hips and thighs. This can make movements like standing up from a chair, climbing stairs, or walking feel physically difficult, because the muscles aren’t receiving strong enough signals to sustain the effort, says Andrea Jaworek, a physical therapist at the Ohio State University Wexner Medical Center in Ohio.

Muscle weakness can involve other muscle groups in your arms, as well as those involved in swallowing and speech.

The ‘Warm-Up’ Phenomenon

One unique feature of LEMS is the “warm-up” effect, where muscle strength may briefly improve with repeated movement. It can be used to help with more challenging activities — for example, marching in place before walking up the stairs.

“I describe it as needing to ‘prime’ your body,” says Kathryn Jira, a physical therapist at the Ohio State University Wexner Medical Center in Columbus.

But the improvement is temporary and doesn’t prevent fatigue from building over time, she adds.

The Cumulative Effect

While staying active and exercising within safe limits is encouraged, overworking muscles isn’t a good idea. It can lead to increased fatigue or worsening weakness, and that can add up, says Katie Gingras, DPT, a board-certified neurologic physical therapist with UC Health in Cincinnati.

“Patients often notice that their muscles fatigue with activity, but there can also be an overall sense of decreased endurance as the day goes on,” says Dib. Activities that feel manageable in the morning can become much harder later on, as muscle endurance declines, she says.

Getting through the day with LEMS requires a thoughtful approach to how you use your energy.

Effective pacing means breaking tasks into smaller steps, alternating more demanding activities with easier ones, and stopping before fatigue sets in — typically at about 50 to 70 percent of your perceived capacity, says Dib.

The Spoon Theory

When you have LEMS, it can be helpful to think about your energy in terms of something concrete.

Prioritize What Matters Most

Because energy is limited, it’s important to focus on what needs to get done.

Planning your day around times when you have more energy — often earlier in the day — can help you tackle more demanding tasks first, says Dib. “Breaking activities into smaller parts and alternating effort with rest can also help prevent fatigue from building too quickly,” she says.

Gingras agrees: Prioritizing essential tasks and pacing activity can help you accomplish more over the course of a day rather than pushing through until exhaustion.

Modify Tasks to Conserve Energy

Small adjustments to how you perform everyday activities can significantly reduce strain.

“Simple changes like sitting instead of standing, using a cart to move items, or keeping frequently used objects within easy reach can lower the physical cost of daily tasks,” says Dib.

Assistive equipment can also help you preserve energy for more challenging movement. “This allows you to maintain strength for higher-demand tasks, such as sit-to-stand transfers and stair negotiation,” says Gingras.

She helps her clients remember the key principles of energy conservation by framing them as the “four Ps”:

• Planning Spread out more demanding activities and schedule rest ahead of time.
• Pacing Work in shorter bursts instead of pushing to exhaustion.
• Prioritizing Focus on essential tasks and delegate when possible.
• Positioning Sit instead of stand and use tools to reduce strain.

When you have LEMS, it’s important to rest before you feel tired, says Dib. “Once fatigue sets in, recovery is slower and weakness can temporarily worsen,” she says.

The best approach is to schedule short, regular rest breaks throughout the day rather than rely on long recovery periods, says Dib.

Short breaks — about 5 to 15 minutes after 20 to 40 minutes of activity — can allow partial recovery and maintain more consistent function, she says.

“This approach prevents deeper fatigue that is harder to reverse and helps stabilize performance,” says Dib.

Jaworek agrees: Staying ahead of fatigue — instead of playing catch-up once exhaustion sets in — can make it easier for muscles to recover.

Medication, particularly amifampridine, can complement pacing strategies by improving neuromuscular transmission, says Dib.

Prescribed under the brand names Ruzurgi and Firdapse, amifampridine works by blocking potassium channels in nerve endings, she says. This makes it easier for nerves to send stronger signals to the muscles, which can improve muscle strength and reduce fatigue.

“It often starts working quickly, within about 30 to 60 minutes, and many people notice a difference the same day they begin taking it,” says Jira.

While amifampridine doesn’t prevent or reverse muscle weakness and fatigue, it can help make everyday activities like standing, walking, or climbing stairs feel easier — and make day-to-day life much more manageable, she says.

Though helpful in reducing fatigue for periods throughout the day, amifampridine doesn’t eliminate it or fully normalize strength, so behavioral strategies like pacing and safe movement techniques remain essential, says Dib.

• Lambert-Eaton myasthenic syndrome (LEMS) causes muscle weakness and fatigue because signals from the nerves do not fully reach the muscles.
• Strategic pacing and energy conservation — such as breaking tasks into smaller steps and sitting instead of standing — can help you stay active while preventing overexertion.
• While medications like amifampridine can improve muscle strength and reduce fatigue, they should be used in combination with behavioral strategies like the "four Ps": planning, pacing, prioritizing, and positioning.