Can regional phase angle reflect changes in physical fitness and body composition from late childhood to adolescence? A cohort study.

Changes in arm phase angle were associated with changes in handgrip strength in both girls and boys.

• ΔPhA-Arm was associated with ΔHS with β = 0.23 in girls and β = 0.24 in boys
• Participants were from the Physical Activity and Nutrition in Children (PANIC) study, n=270 (122 girls)
• Measurements taken at ages 9.7 ± 0.4 years (T1) and 15.8 ± 0.4 years (T2)
• Regression models were adjusted for pubertal status

Changes in arm phase angle were associated with changes in standing long jump performance in both sexes.

• ΔPhA-Arm was associated with ΔSLJ with β = 0.29 in girls and β = 0.38 in boys
• Standing long jump was scaled by body mass
• Associations were adjusted for pubertal status

Changes in arm phase angle were associated with changes in total lean mass in both sexes.

• ΔPhA-Arm was associated with ΔLM with β = 0.33 in girls and β = 0.45 in boys
• Lean mass was determined by dual-energy X-ray absorptiometry (DXA)
• The association was stronger in boys than in girls

Changes in arm phase angle were associated with changes in fat mass percentage in boys but not girls.

• ΔPhA-Arm was associated with Δ%FM with β = -0.22 in boys only
• Fat mass percentage was determined by DXA
• The negative beta coefficient indicates that increases in arm PhA were associated with decreases in fat mass percentage

Changes in leg phase angle were associated with changes in handgrip strength in boys only.

• ΔPhA-Leg was associated with ΔHS with β = 0.29 in boys
• No significant association was observed for girls
• Handgrip strength was scaled by body mass

Changes in leg phase angle were associated with changes in standing long jump in both sexes.

• ΔPhA-Leg was associated with ΔSLJ with β = 0.23 in girls and β = 0.25 in boys
• Associations were adjusted for pubertal status

Changes in leg phase angle were associated with changes in peak oxygen uptake in girls only.

• ΔPhA-Leg was associated with ΔVO₂peak with β = 0.25 in girls
• No significant association was observed for boys
• VO₂peak was measured using a cycle ergometer test and scaled by lean mass

Changes in leg phase angle were associated with changes in lean mass in both sexes, with a stronger association in boys.

• ΔPhA-Leg was associated with ΔLM with β = 0.26 in girls and β = 0.59 in boys
• The association in boys (β = 0.59) was notably stronger than in girls (β = 0.26)
• Lean mass was determined by DXA

Changes in leg phase angle were associated with changes in fat mass percentage in both sexes, but in opposite directions.

• ΔPhA-Leg was associated with Δ%FM with β = 0.20 in girls and β = -0.24 in boys
• The positive association in girls and negative association in boys suggest sex-specific relationships between leg phase angle and fat mass changes

Changes in regional phase angle positively predicted handgrip strength and standing long jump at adolescence in both sexes.

• At T2, ΔR-PhA positively predicted HS and SLJ in both sexes
• Regression models predicting T2 outcomes were adjusted for baseline outcome, body composition, pubertal status, and moderate-to-vigorous physical activity at T1
• This finding held for both arm and leg phase angle measures

Changes in arm phase angle predicted lean mass at adolescence in girls, while changes in regional phase angle predicted lean mass in boys.

• ΔR-PhA positively predicted LM in boys at T2
• ΔPhA-Arm predicted LM in girls at T2
• Lean mass was assessed by DXA at both time points

The study used a longitudinal cohort design spanning approximately six years from late childhood to adolescence.

• 270 participants (122 girls) from the Physical Activity and Nutrition in Children (PANIC) study were analyzed
• Baseline age was 9.7 ± 0.4 years (T1) and follow-up age was 15.8 ± 0.4 years (T2)
• Multifrequency BIA provided regional phase angle measures for arm and leg
• DXA was used as the reference method for body composition assessment