Limits...
Sex differences in response to maximal exercise stress test in trained adolescents.

Fomin Å, Ahlstrand M, Schill HG, Lund LH, Ståhlberg M, Manouras A, Gabrielsen A - BMC Pediatr (2012)

Bottom Line: Peak VO(2) was lower in females (2.37 ± 0.34 l/min) than in males (3.38 ± 0.49 l/min, P < 0.05).When peak VO(2) was normalized to leg muscle mass sex differences disappeared (females: 161 ± 21 ml/min/kg vs. males: 170 ± 23 ml/min/kg).The increase in cardiac index during exercise is the key factor responsible for the greater peak VO(2) in adolescent boys compared to girls.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Cardiology, Karolinska Institutet, Karolinska University Hospital, N1:05, SE-17176, Stockholm, Sweden.

ABSTRACT

Background: Sex comparisons between girls and boys in response to exercise in trained adolescents are missing and we investigated similarities and differences as a basis for clinical interpretation and guidance.

Methods: A total of 24 adolescent females and 27 adolescent males aged 13-19 years underwent a maximal bicycle exercise stress test with measurement of cardiovascular variables, cardiac output, lung volumes, metabolic factors/lactate concentrations and breath-by-breath monitoring of ventilation, and determination of peak VO(2).

Results: Maximum heart rate was similar in females (191 ± 9 bpm) and males (194 ± 7 bpm), cardiac index at maximum exercise was lower in females (7.0 ± 1.0 l/min/m(2)) than in males (8.3 ± 1.4 l/min/m(2), P < 0.05). Metabolic responses and RQ at maximum exercise were similar (females: 1.04 ± 0.06 vs. males: 1.05 ± 0.05). Peak VO(2) was lower in females (2.37 ± 0.34 l/min) than in males (3.38 ± 0.49 l/min, P < 0.05). When peak VO(2) was normalized to leg muscle mass sex differences disappeared (females: 161 ± 21 ml/min/kg vs. males: 170 ± 23 ml/min/kg). The increase in cardiac index during exercise is the key factor responsible for the greater peak VO(2) in adolescent boys compared to girls.

Conclusions: Differences in peak VO(2) in adolescent boys and girls disappear when peak VO(2) is normalized to estimated leg muscle mass and therefore provide a tool to conduct individual and intersex comparisons of fitness when evaluating adolescent athletes in aerobic sports.

Show MeSH

Related in: MedlinePlus

Oxygen uptake in boys and girls. Peak oxygen uptake (peak VO2, l/min) and peak oxygen uptake normalized to total body mass (ml/min/kg), normalized to estimated fat free mass (ml/min/kg lean body weight), and normalized to estimated total leg muscle mass (ml/min/kg leg muscle) in female (♀, N = 23) and male (♂, N = 27) subjects. *) denotes statistical significant difference (p < 0.05 by unpaired t-test with correction for multiple comparisons) between female and male subjects with regard to peak VO2, peak VO2 normalized to total body mass and estimated lean body mass, but not comparing peak VO2 normalized to estimated leg muscle mass.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3472286&req=5

Figure 2: Oxygen uptake in boys and girls. Peak oxygen uptake (peak VO2, l/min) and peak oxygen uptake normalized to total body mass (ml/min/kg), normalized to estimated fat free mass (ml/min/kg lean body weight), and normalized to estimated total leg muscle mass (ml/min/kg leg muscle) in female (♀, N = 23) and male (♂, N = 27) subjects. *) denotes statistical significant difference (p < 0.05 by unpaired t-test with correction for multiple comparisons) between female and male subjects with regard to peak VO2, peak VO2 normalized to total body mass and estimated lean body mass, but not comparing peak VO2 normalized to estimated leg muscle mass.

Mentions: Maximum systolic blood pressure during exercise was lower in female (171 ± 20 mmHg) than in male subjects (185 ± 17 mmHg, p < 0.05), whereas maximum heart rate was similar (females: 191 ± 9 bpm vs. males 194 ± 7 bpm, Figure 1). Cardiac index at maximum exercise was lower in females (7.0 ± 1.0 l/min/m2) than in males (8.3 ± 1.4 l/min/m2, P < 0.05, Figure 1). Ventilation and ventilated lung volume at maximum exercise were significantly lower in females than in males (P < 0.05, Table 2), whereas metabolic responses to maximum exercise were very similar with only a minor incremental increase in blood lactate levels in males compared to females and without differences in blood pH, blood base excess, or blood HCO3- (Table 2). Peak VCO2 were lower in females (2.45 ± 0.36 l/min) than in males (3.50 ± 0.51 l/min) but was matched to peak VO2 in a similar manner in both sexes as RQ at maximum exercise was similar (females: 1.04 ± 0.06 vs. males: 1.05 ± 0.05). Absolute peak VO2, peak VO2 normalized to total body mass, and peak VO2 normalized to lean body mass were lower in females (2.37 ± 0.34 l/min; 39.1 ± 5.1 ml/min/kg; 51.2 ± 6.8 ml/min/kg, respectively) compared to males (3.38 ± 0.49 l/min; 48.7 ± 5.5 ml/min/kg; 56.0 ± 7.6 ml/min/kg, respectively, P < 0.05; Figure 2), but when peak VO2 was normalized to leg muscle mass sex differences disappeared (females: 161 ± 21 ml/min/kg vs. males: 170 ± 23 ml/min/kg; Figure 2). Normalization of peak VO2 to estimated leg muscle mass, when compared to normalization to total body mass/lean body mass had an impact on the classification rank of training-level in girls. In our group of girls, 25% (N = 6) were reclassified and shifted from the half of subjects with peak VO2 below the median to the group above the median when normalization to total body mass/lean body mass was compared to peak VO2 normalization to estimated leg muscle mass. This impact of normalization on classification rank of training-level was less apparent in boys (2 subjects reclassified) – mainly because their estimated fat mass in legs exhibits very low levels with low variation.


Sex differences in response to maximal exercise stress test in trained adolescents.

Fomin Å, Ahlstrand M, Schill HG, Lund LH, Ståhlberg M, Manouras A, Gabrielsen A - BMC Pediatr (2012)

Oxygen uptake in boys and girls. Peak oxygen uptake (peak VO2, l/min) and peak oxygen uptake normalized to total body mass (ml/min/kg), normalized to estimated fat free mass (ml/min/kg lean body weight), and normalized to estimated total leg muscle mass (ml/min/kg leg muscle) in female (♀, N = 23) and male (♂, N = 27) subjects. *) denotes statistical significant difference (p < 0.05 by unpaired t-test with correction for multiple comparisons) between female and male subjects with regard to peak VO2, peak VO2 normalized to total body mass and estimated lean body mass, but not comparing peak VO2 normalized to estimated leg muscle mass.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472286&req=5

Figure 2: Oxygen uptake in boys and girls. Peak oxygen uptake (peak VO2, l/min) and peak oxygen uptake normalized to total body mass (ml/min/kg), normalized to estimated fat free mass (ml/min/kg lean body weight), and normalized to estimated total leg muscle mass (ml/min/kg leg muscle) in female (♀, N = 23) and male (♂, N = 27) subjects. *) denotes statistical significant difference (p < 0.05 by unpaired t-test with correction for multiple comparisons) between female and male subjects with regard to peak VO2, peak VO2 normalized to total body mass and estimated lean body mass, but not comparing peak VO2 normalized to estimated leg muscle mass.
Mentions: Maximum systolic blood pressure during exercise was lower in female (171 ± 20 mmHg) than in male subjects (185 ± 17 mmHg, p < 0.05), whereas maximum heart rate was similar (females: 191 ± 9 bpm vs. males 194 ± 7 bpm, Figure 1). Cardiac index at maximum exercise was lower in females (7.0 ± 1.0 l/min/m2) than in males (8.3 ± 1.4 l/min/m2, P < 0.05, Figure 1). Ventilation and ventilated lung volume at maximum exercise were significantly lower in females than in males (P < 0.05, Table 2), whereas metabolic responses to maximum exercise were very similar with only a minor incremental increase in blood lactate levels in males compared to females and without differences in blood pH, blood base excess, or blood HCO3- (Table 2). Peak VCO2 were lower in females (2.45 ± 0.36 l/min) than in males (3.50 ± 0.51 l/min) but was matched to peak VO2 in a similar manner in both sexes as RQ at maximum exercise was similar (females: 1.04 ± 0.06 vs. males: 1.05 ± 0.05). Absolute peak VO2, peak VO2 normalized to total body mass, and peak VO2 normalized to lean body mass were lower in females (2.37 ± 0.34 l/min; 39.1 ± 5.1 ml/min/kg; 51.2 ± 6.8 ml/min/kg, respectively) compared to males (3.38 ± 0.49 l/min; 48.7 ± 5.5 ml/min/kg; 56.0 ± 7.6 ml/min/kg, respectively, P < 0.05; Figure 2), but when peak VO2 was normalized to leg muscle mass sex differences disappeared (females: 161 ± 21 ml/min/kg vs. males: 170 ± 23 ml/min/kg; Figure 2). Normalization of peak VO2 to estimated leg muscle mass, when compared to normalization to total body mass/lean body mass had an impact on the classification rank of training-level in girls. In our group of girls, 25% (N = 6) were reclassified and shifted from the half of subjects with peak VO2 below the median to the group above the median when normalization to total body mass/lean body mass was compared to peak VO2 normalization to estimated leg muscle mass. This impact of normalization on classification rank of training-level was less apparent in boys (2 subjects reclassified) – mainly because their estimated fat mass in legs exhibits very low levels with low variation.

Bottom Line: Peak VO(2) was lower in females (2.37 ± 0.34 l/min) than in males (3.38 ± 0.49 l/min, P < 0.05).When peak VO(2) was normalized to leg muscle mass sex differences disappeared (females: 161 ± 21 ml/min/kg vs. males: 170 ± 23 ml/min/kg).The increase in cardiac index during exercise is the key factor responsible for the greater peak VO(2) in adolescent boys compared to girls.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Cardiology, Karolinska Institutet, Karolinska University Hospital, N1:05, SE-17176, Stockholm, Sweden.

ABSTRACT

Background: Sex comparisons between girls and boys in response to exercise in trained adolescents are missing and we investigated similarities and differences as a basis for clinical interpretation and guidance.

Methods: A total of 24 adolescent females and 27 adolescent males aged 13-19 years underwent a maximal bicycle exercise stress test with measurement of cardiovascular variables, cardiac output, lung volumes, metabolic factors/lactate concentrations and breath-by-breath monitoring of ventilation, and determination of peak VO(2).

Results: Maximum heart rate was similar in females (191 ± 9 bpm) and males (194 ± 7 bpm), cardiac index at maximum exercise was lower in females (7.0 ± 1.0 l/min/m(2)) than in males (8.3 ± 1.4 l/min/m(2), P < 0.05). Metabolic responses and RQ at maximum exercise were similar (females: 1.04 ± 0.06 vs. males: 1.05 ± 0.05). Peak VO(2) was lower in females (2.37 ± 0.34 l/min) than in males (3.38 ± 0.49 l/min, P < 0.05). When peak VO(2) was normalized to leg muscle mass sex differences disappeared (females: 161 ± 21 ml/min/kg vs. males: 170 ± 23 ml/min/kg). The increase in cardiac index during exercise is the key factor responsible for the greater peak VO(2) in adolescent boys compared to girls.

Conclusions: Differences in peak VO(2) in adolescent boys and girls disappear when peak VO(2) is normalized to estimated leg muscle mass and therefore provide a tool to conduct individual and intersex comparisons of fitness when evaluating adolescent athletes in aerobic sports.

Show MeSH
Related in: MedlinePlus