Purpose:
To compare the pattern of the electrical activation of the vastus lateralis muscle during a maximal exercise test between children born prematurely and full-term.

Methods:
The study was conducted in preterm children born at less than 37 weeks of gestational age with a birth weight of less than 1500 g aged 6–9 years compared with children born at term of the same age. A rapidly incremental exercise test on a treadmill was performed, and surface electromyography signals of the vastus lateralis muscle were collected throughout the test. The root mean square (RMS) was calculated every minute. The Mann-Whitney and Friedman’s tests were applied to verify the differences in each minute between and within groups, and nonlinear regression analysis was performed to establish the factors associated with the pattern of vastus lateralis activation.

Results:
Overall, 68 children were analysed: 37 in the premature group and 31 in the term group. The preterm group showed higher RMS values than the full-term group throughout the test, with significant differences at rest and in the 3rd, 4th, 5th, and 6th minutes of the exercise test. Particularly, the preterm group presented 28.5% higher RMS values than the term group throughout the analysed period.

Conclusions:
The lower limbs of the children born prematurely showed higher excitability than those of the children born at full-term. These data could help maintain and/or improve their physical ability during exercise tests.