Description
PURPOSE: to determine whether acute exercise in the heat alters 24-hr breastmilk production and composition among lactating women. METHODS: Seven participants (34±5yrs, 163.7±4.8cm, 66.7±3.0kg, 25.0±14.2 weeks postpartum) completed the study. Participants were eligible if they were breastfeeding (6-week to 12-month infants), aged 18-45 years old, and delivered between 37 and 42 weeks. The study was a randomized, crossover design with three visits: 1) baseline and metabolic heat production testing; 2) acute exercise in the heat (HOT; 36°C, 40% relative humidity[RH]), and 3) acute exercise in a thermoneutral environment (THERM; 20°C, 20%RH). Participants walked for 60 minutes at 8 watts per total body weight (W/kg; 3.0-4.1mph). Core temperature (Tcore), Skin temperature (Tsk), and heart rate (HR) were measured during exercise. Lactation performance was assessed by logging lactation frequency (LF) and 24-hour breast milk production before (PRE24) and after (POST24) each trial using an infant scale. Breastmilk lipid (kcal[Equation]dL-1) and energy (g[Equation]L-1) composition was analyzed at PRE24, 1 hour post (POST1), and POST24 exercise via the creamatocrit technique. Statistical analyses were performed using paired t-tests and repeated measures analysis of variance. Data are presented as mean ± standard deviation. RESULTS: Max Tcore and Tsk (°C) were higher in HOT (Tcore:38.25±0.60, Tsk:35.9±0.4) compared to THERM (Tcore:37.79±0.33, Tsk:31.62±1.31; p=0.045, p< 0.001, respectively). Max HR (bpm) was higher in HOT (p=0.012). Total milk production (mL) and LF (feeds) did not differ between HOT (milk production, LF: PRE24=648.1±275.1mL, 6±1; POST24=618.1±357.1, 6±2) and THERM (milk production, LF: PRE24=24:774.3±381.9, 7±2; POST24=707.5±300.3mL, 7±2). There were no differences in breastmilk lipid content between HOT (PRE24=46.05±16.90, POST1=35.14±12.48, POST24=43.69±9.96) and THERM (PRE24=38.89±18.56, POST1=33.64±21.08, POST24=32.75±19.67; p=0.969). There were no differences in breastmilk energy content (p=0.759).CONCLUSION: Despite elevated thermoregulatory strain during exercise in HOT, acute exercise in the heat did not adversely affect lactation performance in lactating women.
Publisher
Providence College
Date
Spring 4-22-2026
Start Date
4-22-2026 11:00 AM
Type
Poster
Format
Text
.pdf (text under image)
Language
English
