The same Pilates exercises were performed during the Mat Pilates and Reformer apparatus sessions. For each exercise, one set of 10 repetitions was performed. Between each exercise, participants were allowed to rest for 2 minutes in a lying position. For each exercise in the Reformer apparatus, the number of springs used was defined during the familiarization sessions as the highest number of springs the participant could perform the 10 repetitions of the exercise with proper technique and following the 5 Pilates principles correctly. The exercises performed were (Stott 2003; Stott 2001): 1) Cat stretch; 2) Hip rolls; 3) Ab prep; 4) Breast stroke preps; 5) Hundred; 6) Breast stroke; 7) Half roll back; 8) Single leg stretch; 9) Slow double leg stretch; 10) Double leg stretch; 11) Double leg circle; 12) Scissors; 13) Roll over; 14) Teaser; 15) Spine stretch forward.

The same Pilates exercises were performed during the Mat Pilates and Reformer apparatus sessions. For each exercise, one set of 10 repetitions was performed. Between each exercise, participants were allowed to rest for 2 minutes in a lying position. For each exercise in the Reformer apparatus, the number of springs used was defined during the familiarization sessions as the highest number of springs the participant could perform the 10 repetitions of the exercise with proper technique and following the 5 Pilates principles correctly. The exercises performed were (Stott 2003; Stott 2001): 1) Cat stretch; 2) Hip rolls; 3) Ab prep; 4) Breast stroke preps; 5) Hundred; 6) Breast stroke; 7) Half roll back; 8) Single leg stretch; 9) Slow double leg stretch; 10) Double leg stretch; 11) Double leg circle; 12) Scissors; 13) Roll over; 14) Teaser; 15) Spine stretch forward.

The participants attended two half-hour Pilates exercise classes twice a week, for one month, to familiarize themselves with the exercises and to learn the 5 Pilates' principles. After the learning period, two experimental sessions were performed: a Mat Pilates session and a Reformer apparatus Pilates session. The order of each session was randomized and drawn beforehand. Each experimental session lasted about one and a half hours and the interval between the sessions was 48 hours. Participants were asked to not perform any exercise and to refrain from food or fluids except water eight hours prior to each experimental session. Prior to the start of the experimental sessions, participants received a standard breakfast of 321 kcal that was 76% (61 g) carbohydrate, 8% (6,7 g) protein, 16% (5,9) fat, provided by the study researchers. All sessions were conducted at the same time in the morning, and the room temperature (22°C) and humidity (40-50%) were controlled during the whole session.

VO2 was measured continuously for both Mat and Reformer apparatus Pilates as described previously. Data were calculated on breath-by-breath intervals at rest and during exercise. The absolute EE in kilocalories per minute was estimated using a constant value of 5.05 kcal.L-1 O2, so the O2 values expressed in L/min were multiplied by 5.05. VO2 values in ml/min/kg were also considered for the analysis.

Capillary blood samples were collected from a fingertip before the first exercise and immediately after the last exercise of the Mat Pilates and Reformer apparatus experimental sessions. These samples were added into a 3mL eppendorf tube with sodium fluorite and this mixture was frozen to be further analyzed via spectrophotometry using a YSI 2300 STAT Plus (Yellow Springs Instrument, Yellow Springs, Ohio, USA).