BackgroundCardiorespiratory　fitness　(CRF)　is　a　critical　indicator　of　overall　health,　while　the　glycation　gap　(G-Gap)　emerges　as　a　potential　novel　biomarker　for　metabolic　and　cardiovascular　risk　assessment.　However,　the　relationship　between　G-Gap　and　CRF　remains　incompletely　understood.ObjectiveTo　investigate　the　association　between　glycation　gap　and　impaired　CRF,　and　evaluate　its　potential　as　an　early　health　risk　indicator.MethodsUsing　data　from　the　National　Health　and　Nutrition　Examination　Survey　(NHANES,　1999-2004),　we　conducted　a　comprehensive　analysis　of　3,818　adult　participants.　G-Gap　was　calculated　by　standardizing　glycated　albumin　(GA)　and　glycated　hemoglobin　(HbA1c)　levels,　comparing　actual　and　predicted　HbA1c　values.　Cardiorespiratory　fitness　was　assessed　through　maximal　oxygen　uptake　(VO2　max),　with　impaired　CRF　defined　as　performance　below　the　20th　percentile　for　gender　and　age-specific　thresholds.　Multivariate　logistic　regression　models　were　employed,　adjusting　for　demographic　characteristics,　laboratory　parameters,　and　potential　confounding　factors.ResultsIn　unadjusted　models,　For　every　1　increase　in　G-Gap　as　a　continuous　variable,　the　chance　of　CRF　damage　increased　by　65%　(OR　1.65,　95%　CI　1.29-2.11).　After　comprehensive　covariate　adjustment,　the　association　remained　statistically　significant,　with　odds　ratios　of　1.87　(95%　CI　1.41-2.49)　in　partially　adjusted　and　1.41　(95%　CI　1.01-1.98)　in　fully　adjusted　models.　Quartile　analysis　revealed　significantly　higher　risks　of　impaired　CRF　in　the　third　and　fourth　G-Gap　quartiles　compared　to　the　first　quartile.ConclusionsThis　study　demonstrates　an　association　between　higher　G-Gap　values　and　an　increased　likelihood　of　impaired　CRF.