Effects of a SMART Goal Setting and 12-Week Core Strength Training Intervention on Physical Fitness and Exercise Attitudes in Adolescents: A Randomized Controlled Trial

This study aimed to analyze the impacts of a 12-week core strength training (CST) and goal-setting (GS) program on the core endurance, agility, sprinting, jumping, grip strength, and exercise attitude in a group of adolescents. This study followed a randomized parallel design in which 362 adolescents (age: 14.5 ± 1.07 years; body mass index: 19.82 ± 3.64) were allocated to a GS (n = 89), CST (n = 92), or GS + CST (n = 90) program or to a control group (n = 91). Participants were assessed two times (baseline and postintervention) for the following tests: (i) 50 m dash, (ii) grip strength, (iii) long jump, (iv) 1000 m running for boys and 800 m for girls, (v) core endurance, and (vi) exercise attitude. Significant differences (p < 0.05, η2p = 0.035−0.218) were found between the four groups of the six components of physical fitness and the three components of attitude toward exercise (target attitudes, behavioral habits, and sense of behavioral control). Between-group analysis revealed that the GS + CST had significant advantages (p < 0.05) over the CON in terms of the 50 m dash (Cohen’s d = 0.06), grip strength (Cohen’s d = 0.19_left, 0.31_right), 800/1000 m running (Cohen’s d = 0.41), core endurance (Cohen’s d = 0.95), and sense of behavioral control (Cohen’s d = 0.35). Between-group analysis also revealed that the CST had significant advantages over the CON in terms of grip strength (Cohen’s d = 0.27_left, 0.39_right), 50 m (Cohen’s d = 0.04), long jump (Cohen’s d = 0.21), 800/1000 m (Cohen’s d = 0.09), and core stability (Cohen’s d = 0.63), which were significantly different from CON (p < 0.05). GS differed from CON only on 50 m (Cohen’s d = 0.02) and core stability (Cohen’s d = 0.13) with a small effect (p < 0.05). We conclude that the combined intervention of GS and CST is more effective in promoting fitness in adolescents, i.e., GS + CST > CST and GS + CST > GS.