Effects of Detraining on Left Ventricular Mass in Endurance-Trained Individuals: A Systematic Review and Meta-Analysis.

Detraining refers to a loss of training adaptations resulting from reductions in training stimulus due to illness, injury, or active recovery breaks in a training cycle and is associated with a reduction in left ventricular mass (LVM). The purpose of this study was to conduct a systematic review and meta-analysis to determine the influence of detraining on LVM in endurance-trained, healthy individuals. Using electronic databases (e.g., EMBASE & MEDLINE), a literature search was performed looking for prospective detraining studies in humans. Inclusion criteria were: adults, endurance-trained individuals with no known chronic disease, detraining intervention >1 week, and pre- and post-detraining LVM reported. A pooled statistic for random effects was used to assess changes in LVM with detraining. Fifteen investigations (19 analyses) with a total of 196 participants (ages 18 to 55 years, 15% female) met inclusion criteria, with detraining ranging between 1.4 and 15 weeks. The meta-analysis revealed a significant reduction in LVM with detraining (standardized mean difference = -0.586; 95%CI = -0.817, -0.355, p<0.001). Independently, length of detraining was not correlated with the change in LVM. However, a meta-regression model revealed length of the detraining, when training status was accounted for, was associated with the reduction of LVM (Q=15.20, df=3, p=0.0017). Highly trained/elite athletes had greater reductions in LVM compared with recreational and newly trained individuals (p<0.01). Limitations included limited number of female participants and inconsistent reporting of intervention details. In summary, LVM is reduced following detraining of one week or more. Further research may provide a greater understanding of the effects of sex, age and type of detraining, on changes in LVM in endurance-trained individuals.