A study has revealed that pre-training glycemic level has considerable effect on exercise-induced improvements.

A total of 105 overweight people with an average age of 61, who suffered from impaired glucose tolerance or type 2 diabetes mellitus (T2DM), participated in a 12-to 16-week period of aerobic exercise training.
Researchers measured the participants' body composition, aerobic fitness, and glycemic control, and assessed the relationships between pre-intervention variables and intervention-induced changes.
Average change in body weight, whole-body fat, fasting plasma glucose and 2-hour oral glucose tolerance test (OGTT) were significantly improved following exercise training.
However, researchers found that aerobic exercise-induced improvements in glycemic control were reduced by ambient hyperglycemia, particularly in participants with T2DM.
Source-ANI