Author(s): ALVES, I., CASTRO, M.A., TAVARES, S., ALVES, E., FERNANDES, O., Institution: UNIVERSITY OF ÉVORA, Country: PORTUGAL, Abstract-ID: 1443

INTRODUCTION:
Achondroplasia (ACH) is a rare skeletal dysplasia characterised by short disproportionate stature, increased cardiovascular disease and tendency to obesity [1]. Reduced physical fitness, muscle strength and lung capacity have been reported in adults with achondroplasia (AwACH) [2]. The cardiorespiratory functional capacity is influenced by body size, physical activity level (PAL), and genetics [3]. We hypothesise that higher levels of regular physical activity are associated with better physical fitness, lower adiposity, and cardiometabolic optimization in AwACH.
METHODS:
Participants performed a maximal treadmill exercise test to measure metabolic parameters: VO2max, peak VO2 (pVO2), peak ventilation (pV), maximum heart rate (maxHR), anaerobic threshold (AT), and functional Capacity (FC). Anthropometrics were collected and body composition parameters as fat mass (FM%), lean mass (LM%) and water (BW%) percentages, were estimated by bioimpedance. Physical fitness, with the 6 minutes walking test (6MWT) and strength test by handgrip strength (HGS) were performed. The International Physical Activity questionnaire (IPAQ) was self-administered to obtain a PA score (PAS) and PAL.
RESULTS:
Seven AwACH, 4 women, mean age 37.3±11.9 years, body weight 53.7±15.2kg and height 129.0±13.9cm. Based on PAS (723±768 MET-min/week), two groups were identified: PAL1 (n=5) and PAL2 (n=2), inactive and minimally active, respectively. Multivariate analyses revealed PAL2 significantly outperformed PAL1 across functional exercise capacity and cardiovascular fitness indicators. Significant differences (p<0.05) existed between groups in favour of PAL2 on FC (3.924), pVO2 (2.847), VO2max (4.055), AT (2.564), 6MWT (3.03), PAS (3.176) and height (3.752). PAL2 participants showed lesser 15.52% FM% and 2.7bpm maxHR. Strong correlations (p<0.001) existed between HGS and pV (0.955), VO2max and PAS (0.967) and FM% (-0.842), indicating lower cardiometabolic risk, favouring PAL2. Other correlations (p<0.01) were found between pVO2 and HGS (0.939), bW (0.928) and LM with AT (0.873). VO2max predictors were identified: FM (R2=0.709) and 6MWT (R2=0.699), p<0.01.
CONCLUSION:
These preliminary results show that increased PA is associated with cardiorespiratory function in AwACH, which can improve cardiometabolic health. Higher PAL showed association with lower FM% mass and maxHR. The 6MWT and HGS may represent surrogate markers of fitness and are promising clinical proxies for exercise tolerance in AwACH. Results provide insights in developing strategies to increase PA among AwACH for cardiometabolic optimization.

References
1.Hoover-Fong J, et al., Lifetime impact of achondroplasia. Bone. 2021 May; 146:115872.
2. de Vries O, et al., Physical fitness and activity level in Norwegian adults with achondroplasia. AmJMedGenet, 2021 Apr;185(4):1023-1032.
3.Mezzani A et al., Standards for the use of cardiopulmonary exercise testing for the functional evaluation. EJCardiov Prev Rehabil. 2009 Jun;16(3):249-67