Impact of 6-Week Combined Gym and Climbing Training on Handgrip Strength and Arm Size—GRIP-6 Study

<b>Background</b>: Climbing and strength training are among the most popular types of sports among recreational athletes. However, many newcomers quickly lose motivation and abandon training due to a lack of visible and athletic progress. Hence, we assessed whether a 6-week combined structured gym and climbing training could improve arm muscle strength and size. <b>Methods</b>: We recruited 25 healthy recreational athletes (14 [56.0%] females, age = 20.4 ± 1.7 years, BMI = 21.8 ± 1.7 kg·m^-2). Most participants trained several times per week (N = 12, 48.0%), and training sessions lasted between 1 and 2 h (N = 11, 44.0%). Most athletes rated their current fitness level as "very good" (N = 15, 60.0%). Subjects performed two gym sessions and two climbing training sessions per week and avoided other training for 6 weeks. We measured the time of bar hang, handgrip strength, and forearm circumference before and after 6 weeks. <b>Results</b>: Hanging time increased from 55.3 ± 3.2 s to 60.9 ± 31.3 s (t(24) = 6.68, <i>p</i> < 0.001). Right handgrip strength increased from 31.6 ± 8.4 N to 34.3 ± 7.6 N (t(24) = 5.58, <i>p</i> < 0.001). Left handgrip strength increased from 29.4 ± 9.9 N to 31.0 ± 9.8 N (t(24) = 4.62, <i>p</i> < 0.001). Right forearm circumference increased from 24.6 ± 1.5 cm to 25.4 ± 1.7 cm (t(24) = 9.04, <i>p</i> < 0.001). Left forearm circumference increased from 24.6 ± 2.0 cm to 25.1 ± 2.1 cm (t(24) = 5.94, <i>p</i> < 0.001). All the relationships remained significant when stratified between males (<i>p</i> < 0.001-0.003) and females (<i>p</i> < 0.001-0.008). <b>Conclusions</b>: A 6-week training intervention consisting of structured climbing and strength training induces significant improvements in grip strength and the appearance of arm muscles in recreational athletes. Amateurs could benefit even from shorter training mesocycles, as a 6-week window to see visible progress.