Background: The benefit and safety of exercise training for patients with neuromuscular disorders has long been a contentious topic. This is, in part, due to recognised challenges associated with rare diseases including small and heterogenous patient populations. We performed a systematic review and meta-analyses to evaluate the effectiveness and safety of interventional exercise and establish minimal clinically important differences (MCID) in outcome measures in neuromuscular disorders to facilitate clinical interpretation. Methods: For this systematic review and meta-analyses, we searched MEDLINE, Embase, Scopus, Web of science, SportDiscus and Cochrane Library databases for articles on exercise interventions in patients with NMD, published from inception to Mar 26, 2018. Aerobic, strength, and combined (aerobic and strength) exercise intervention studies in NMD were eligible for inclusion. Meta-analyses was performed to compare outcome measures at baseline with those after at least six weeks of exercise training (i.e. before-after exercise training within individuals). A further meta-analysis was performed to compare outcome measures before-after exercise training between groups (exercise training versus usual care). Impact of disease heterogeneity was explored using a random effect model. Study quality was evaluated via The Cochrane risk of bias tool and NIH Quality Assessment Tool. This study was registered with PROSPERO, number CRD42018102183. Interactive online databases were developed to facilitate full interrogations of data. Findings: We identified 130 articles describing 1,805 participants with 35 different forms of neuromuscular disorders (NMD). Of these studies, 76 were suitable for inclusion in the tabular meta-analyses. Within group and between group meta-analyses showed peak aerobic capacity (SMD 0·56 [95% CI 0·20, 1·10]; p=0·04), and peak power (SMD 0·70 [95% CI 0·15, 1·24]; p=0·01) were able to detect objective changes in exercise capacity. Distance walked (6MWT) (SMD 0·29 [95% CI 0·01, 0·57]; p=0·04), sit-to-stand (STS) (repetitions) (SMD 0·63 [95% CI 0·06, 1·21]; p=0·03), STS (seconds) (SMD -0·67 [95% CI -1·31, 0·03]; p=0·04), rise from supine (SMD -0·50 [95% CI -0·87, -0·13]; p=0·008), SF-36 (SMD 0·70 [95% CI 0·32, 1·07]; p=0·0003), fatigue severity scale (SMD -0·65 [95% CI -1·01, -0·29]; p=<0·0001), citrate synthase (1·81 [95% CI 0·87 to 2·76]; p=0·0002), type 1 fibre area (SMD 0·50 [95% CI 0·19, 0·81]; p=0·002), type II fibre area (SMD 0·63 [95% CI 0·22, 1·05]; p=0·003), and central nuclei (SMD 0·44 [95% CI 0·01 to 0·88]; p=0·04) were only able to detect change within individuals but not between groups (exercise training versus usual care). Ten of 18 meta-analysed articles between groups (exercise training versus usual care) and 30 of 58 meta-analysed articles within-group (before versus after exercise) were judged to be of unclear risk of bias. Substantial I 2 statistic heterogeneity was revealed for STS (seconds) (I²=58·5%; p=0·04) and citrate synthase (I²=70·90%; p=0·002), otherwise heterogeneity for all outcomes was low. No study-related serious adverse events were reported nor significant increases in CK. Interpretation: Exercise training in patients with NMD is safe across a range of systemic outcome measures and appears to cause no harm. With the emergence of new therapeutic strategies, defining minimal clinically important differences (MCID), at this critical juncture, is vital in informing future clinical trial design. Funding Statement: Wellcome Centre for Mitochondrial Research, Newcastle University. Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: This study was registered with PROSPERO, number CRD42018102183 and utilized the PRISMA 2009 checklist.