Evidence is split throughout multiple reviews and papers into two separate categories – those that showed no change in HbA1c and those that showed an improvement in HbA1c.
A 2014 systematic review covering six randomised controlled trials with a total 323 participants found four studies showing an improvement in HbA1c . There is no mention however of the remaining two’s results and the paper goes on to conclude there is insufficient well-designed studies to ascertain the true effect on HbA1c.
A 2019 systematic review of 24 both randomised and non-randomised control studies found that exercise training decreased HbA1c. 
A 2016 systematic review totalling 15 studies covering both t2dm and t1dm found only one study which showed an improvement in T1DM with combined resistance and aerobic training. 
A 2017 systematic review of prospective randomised or controlled trials found no evidence of significant changes in HbA1c. 
A 2013 meta-analysis of 12 both randomised and non-randomised control studies found no evidence of benefit on glycaemia but went on to recommend PA to type 1 diabetics regardless. It aslos stated that glycaemic variability may be a better outcome measure for improvement in glycaemia and this should be studied further. 
A 2018 study of 21 male participants conducting either aerobic or resistance training 2x a week for 3 months showed no significant change in HbA1c for either intervention however a non significant downtrend was seen in the aerobic group. 
A 2011 study of 66 subjects in a T1-DARTE trial to investigate the effects of aerobic and resistance training found no significant difference between aerobic, resistance, both or a sedentary control on HbA1c. 
Quality of evidence
Grade C– Low quality
Strength of recommendation
1 – Strong
Exercise may reduce HbA1c or may produce no change. Evidence seems to suggest that the specific participant and length, frequency and type of exercise intervention may affect the response in HbA1c and further study is needed. Other potential benefits to conducting exercise along with minimal negative effects makes PA a valid recommendation
 – (Yardley JE, Hay J, Abou-Setta AM, Marks SD, McGavock J. A systematic review and meta-analysis of exercise interventions in adults with type 1 diabetes. Diabetes Res Clin Pract. 2014 Dec;106(3):393-400. doi: 10.1016/j.diabres.2014.09.038. Epub 2014 Oct 7. PMID: 25451913)
 – (Ostman C, Jewiss D, King N, Smart NA. Clinical outcomes to exercise training in type 1 diabetes: A systematic review and meta-analysis. Diabetes Res Clin Pract. 2018 May;139:380-391. doi: 10.1016/j.diabres.2017.11.036. Epub 2017 Dec 6. PMID: 29223408)
 – (Chimen, M., Kennedy, A., Nirantharakumar, K. et al. What are the health benefits of physical activity in type 1 diabetes mellitus? A literature review. Diabetologia 55, 542–551 (2012). https://doi.org/10.1007/s00125-011-2403-2)
 – Wu N, Bredin SSD, Guan Y, Dickinson K, Kim DD, Chua Z, Kaufman K, Warburton DER. Cardiovascular Health Benefits of Exercise Training in Persons Living with Type 1 Diabetes: A Systematic Review and Meta-Analysis. Journal of Clinical Medicine. 2019; 8(2):253. https://doi.org/10.3390/jcm8020253
 – Kennedy, A., Nirantharakumar, K., Chimen, M., Pang, T.T., Hemming, K. et al. (2013). Does Exercise Improve Glycaemic Control in Type 1 Diabetes? A Systematic Review and Meta-Analysis. PLoS ONE, 8(3): e58861. doi:10.1371/journal.pone.0058861
 – Röhling, M., Herder, C., Roden, M. et al. (2016). Effects of Long-Term Exercise Interventions on Glycaemic Control in Type 1 and Type 2 Diabetes: a Systematic Review. Experimental and Clinical Endocrinology and Diabetes, 124(8), pp. 487-494.
 – Wróbel, M., Rokicka, D., Czuba, M., Gołaś, A., Pyka, Ł., Greif, M., … Gąsior, M. (2018). Aerobic as well as resistance exercises are good for patients with type 1 diabetes. Diabetes Research and Clinical Practice, 144, 93–101.