Effects of an Acute Strength and Conditioning Training Session on Dual-Energy X-Ray Absorptiometry Results

Abstract

In the use of dual x-ray absorptiometry (DXA) scans to obtain reliable measures of body composition, athletic staff must be aware of acute factors that may alter scan estimates. Although factors such as hydration status and food intake have been shown to alter DXA results (Tinsley, MSSE 2016), it is unknown whether an acute strength and conditioning (S&C) session will alter DXA scan estimates. PURPOSE: To determine if a strength and conditioning (S&C) training session, based upon what athletes regularly engage in, will alter body composition estimates (lean mass, fat mass, and bone mineral content) of a DXA scan. METHODS: The S&C session lasted ~ 90 minutes and consisted of upper and lower body resistance exercises and interval running. Twenty-two strength-trained subjects (15 men, 7 women, age 24 ± 2 yrs, height 174.2 ± 8.5 cm, weight 83.5 ± 15.0 kg) volunteered to participate in the study. A food log was distributed during the informed consent process, which participants maintained for 24 hours prior to the DXA scans. Each subject completed two standard DXA scans on the same day, before and within 45 minutes of completing the S&C session. Participants were instructed to consume a normal, free-living breakfast prior to the first scan, and to then avoid all food intake until completing the second scan. Throughout the S&C session, subjects were encouraged to drink water ad libitum. RESULTS: No significant difference was found on any of the total body measures between pre and post DXA body composition measurements except for total mass, which was found to be lower after the S&C session (pre to post: 83.8-83.5 kg). Compartmental results showed significant differences between pre and post scans in the arms, legs, and trunk. Arm and leg % fat were found to be lower (pre to post: arm % fat 20.5-19.9, leg % fat 23.2-22.6); arm total and lean mass, and leg lean mass were found to be higher (pre to post: arm total mass 10.8-11.0 kg, arm lean mass 8.3-8.5 kg, leg lean mass 21.5-21.8 kg); and trunk lean mass was found to be lower (pre to post: 28.7-28.2 kg) after the S&C session. CONCLUSION: Based on the results of the present study, the acute physiological effects of a S&C session alter body composition measures obtained by DXA scan. Thus, athletic staff should consider the timing of DXA scans in relation to S&C sessions.

Tracking changes in body composition: comparison of methods and influence of pre-assessment standardisation

“…Although numerous studies have documented the potential for transient, artificial changes in body composition estimates in response to food ingestion, fluid intake or exercise (3,(49)(50)(51)(52)(53)(54) , limited prior data have demonstrated the longitudinal implications of these errors (6,38) . In this regard, Kerr et al (6) performed an informative investigation of the consequences of unstandardised assessments before and after a 6-month period of unsupervised training in exercising adults.…”

Acute exercise affects dual‐energy X‐ray absorptiometry body composition estimates but not standardised ultrasound measurements of subcutaneous adipose tissue

“…Reductions in DXA total mass, trunk mass and trunk LM estimates were also observed in strength‐trained individuals following a strength and conditioning session (Lytle et al, 2020). Additionally, the authors observed increased leg mass (200 g) and leg LM (300 g) in all participants but only males increased arm mass (320 g) and arm LM (350 g).…”

“…Reductions in total LM observed in male cyclists were attributed to dehydration whereas decreases in trunk LM in conjunction with increases in arm LM were due to blood volume being shunted from the trunk to the periphery (Nana et al, 2013). Similarly, total body RE combined with interval running ( n = 21, seven females, 24 ± 2 years, ∼ 80 min) before a DXA assessment was observed to decrease trunk LM and arm and leg % fat and increased leg LM estimates (Lytle et al, 2020). Additionally, arm LM increased in male participants but decreased in females.…”

“…It is hypothesised that standardised B‐mode US measurements of SAT and ISAK skinfolds are unlikely to be implicated by prior exercise, with no differences between the sexes (Norton et al, 1998; Wagner & Cotter, 2021). However, prior exercise may compromise the precision of DXA body composition estimates with possible disparate outcomes between males and females (Lytle et al, 2020).…”

Positional Analysis of Body Composition Using Dual-Energy X-Ray Absorptiometry in National Collegiate Athletic Association Division I Football and Men's Lacrosse

“…Previous research (33) has demonstrated that exercise designed to induce dehydration (i.e., thermal chamber and cycling until 2.5% body mass is lost) results in statistically significant alterations to body composition (Δ LM = 1.7 kg, 2.8%). Others (16,22) have documented compositional responses to exercise and feeding in designed experiments more consistent with the conventional athlete training model. Nana et al (22) had subjects undergo DXA after exercise during which they were permitted to eat and hydrate ad libitum.…”