What are the best exercises for individuals with Spinal Muscular Atrophy (SMA)?

Exercise Recommendations for Spinal Muscular Atrophy (SMA)

Combined aerobic and strength training exercises are recommended for individuals with SMA type 3, though current evidence remains very limited and of very low quality. Based on the single available randomized controlled trial, a home-based program combining moderate-intensity aerobic exercise (recumbent cycling) with strength training performed 2-3 times per week appears safe, though efficacy remains uncertain 1.

Aerobic Exercise Protocol

For ambulatory individuals with SMA type 3:

• Frequency: 2-3 days per week 1
• Modality: Recumbent cycle ergometry is preferred over upright cycling due to better trunk support and reduced fatigue 1
• Duration: Progress toward 20-30 minutes per session 1
• Intensity: Moderate intensity (60-65% of peak oxygen uptake or 60-80% peak heart rate) 2

The trial evidence showed that 50% of participants could not achieve the intended aerobic training regimen, highlighting that prescribed intensity may need adjustment based on individual tolerance 1.

Strength Training Protocol

Resistance exercise parameters:

• Frequency: 2 days per week minimum, targeting major muscle groups 1
• Sets and repetitions: Start with 1 set of 10-15 repetitions at low resistance (40% of one-repetition maximum) 2
• Progression: Gradually increase resistance and/or repetitions as tolerated 2
• Rest intervals: Allow at least 48 hours between sessions for any single muscle group 2
• Pattern: Perform exercises in a rhythmical manner at moderate to slow controlled speed through full range of motion 2

The single RCT showed a modest improvement in manual muscle testing scores (mean difference of 11.94 points) in the training group, though this did not reach statistical significance 1.

Functional Outcomes and Monitoring

Expected changes are minimal but potentially meaningful:

• Walking distance on the six-minute walk test showed no detectable difference between exercise and usual care groups (mean difference 9.54 meters, well below the minimal detectable change of 24 meters) 1
• Hammersmith Functional Motor Scale-Expanded scores increased by only 2 points in the training group (below the clinically meaningful threshold of 3 points) 1
• Peak oxygen uptake (VO2max) showed no significant change, with a mean difference of 1.22 mL/kg/min (below the clinically meaningful threshold of 3.5 mL/kg/min) 1

Critical Safety Considerations

Post-exertional symptoms require careful monitoring:

• Screen for respiratory insufficiency and nutritional deficits as contributing factors to post-exertional exhaustion 3
• Chronic malnutrition and negative nitrogen balance are common in SMA patients and contribute to fatigue after high-energy activity 3
• No serious adverse events or withdrawals occurred in the available trial, but this very low-certainty evidence cannot support broader safety conclusions 1

Common Pitfalls to Avoid

Do not prescribe exercise without addressing these factors:

• Avoid high-intensity protocols that 50% of patients cannot complete; start conservatively and progress slowly 1
• Do not ignore respiratory function monitoring, as respiratory decline is a primary concern in SMA 1
• Avoid assuming exercise benefits based on other neuromuscular conditions; SMA-specific evidence is extremely limited 1
• Do not overlook nutritional status, which directly impacts exercise tolerance and recovery 3

Evidence Quality and Clinical Implications

The evidence base is critically weak:

• Only one small RCT (n=14) exists for SMA type 3, with high risk of bias due to lack of participant blinding 1
• The certainty of evidence is very low for all outcomes due to study limitations and imprecision 1
• A 2025 narrative review identified predominantly low to unacceptable quality across 36 rehabilitation intervention studies in SMA, with only 18 studies addressing physiotherapy interventions 4
• Well-designed, adequately powered studies using standardized protocols are urgently needed 1, 4

Emerging Therapeutic Context

Exercise recommendations must consider disease-modifying therapies:

• The landscape of SMA has drastically changed with disease-modifying treatments (nusinersen, onasemnogene abeparvovec), emphasizing the need for comprehensive rehabilitation strategies to maximize functional outcomes 4, 5
• Recent evidence shows epidural spinal cord stimulation can improve motoneuron function, increasing strength (up to +180%), gait quality (+40% step length), and endurance (+26 meters on six-minute walk test) in adults with SMA type 3 6
• These advances highlight that exercise interventions may have greater potential when combined with therapies that address the underlying motoneuron dysfunction 6

Given the very low quality of evidence, proceed cautiously with combined aerobic and strength training at low to moderate intensity, closely monitoring for respiratory decline, nutritional status, and post-exertional symptoms, while recognizing that current evidence cannot definitively establish benefit or harm 1, 4.