Effects of global versus local trunk muscle strength training on muscle strength, proxies of power and rowing-specific performance in pubertal male rowers.

Significant group-by-time interactions were found for all strength, power, and rowing performance outcomes.

• Effect sizes for strength outcomes ranged from d = 3.04 to 3.84 (p < 0.001)
• Effect sizes for power outcomes ranged from d = 0.75 to 2.34 (p < 0.01)
• Effect size for rowing performance was d = 1.61 (p < 0.001)
• Twenty-eight Tier 2 male rowers aged 12-13 years (circa-PHV = 0.2-0.3) completed the study
• Training consisted of a 6-week program with two weekly sessions

Global trunk strength training (GST) produced greater improvements than local trunk strength training (LST) across all measured outcomes.

• Post-hoc analyses indicated greater improvements in GST with effect sizes d = 0.28–1.87 (p < 0.001)
• LST also showed significant improvements with effect sizes d = 0.11–0.73 (p < 0.001)
• GST involved machine-based and free-weight trunk exercises at 70% 1-RM
• LST emphasized body-weight trunk exercises on stable and unstable surfaces
• The authors note that differences in external loading between conditions confound the comparison of exercise modalities

Both GST and LST interventions produced statistically significant within-group improvements in lower- and upper-limb power, trunk strength, and 700-m rowing ergometer performance.

• Pre- and post-tests included lower- and upper-limb power, trunk strength, and a 700-m rowing ergometer test
• LST effect sizes ranged from d = 0.11 to 0.73 (p < 0.001)
• GST effect sizes ranged from d = 0.28 to 1.87 (p < 0.001)
• Participants were pubertal male rowers classified as Tier 2 athletes aged 12–13 years

The differential effects of GST versus LST cannot be attributed solely to trunk muscle recruitment patterns due to the confounding influence of external loading intensity.

• GST used 70% of 1-RM as external loading, whereas LST used athletes' body mass
• The authors state these effects 'likely reflect the combined influence of exercise modality and higher external loading intensity, rather than trunk muscle recruitment patterns alone'
• The authors recommend 'further research controlling for training load is needed to isolate the effects of exercise modality'
• The abstract explicitly states 'differences in external loading between conditions (70% 1-RM vs. athletes' body mass) confound the comparison of GST versus LST modalities'

The study recommends that strength and conditioning specialists consider incorporating GST to enhance foundational strength and power in pubertal male rowers.

• Participants were circa-PHV = 0.2–0.3, indicating they were near peak height velocity
• The 6-week pre-season program was designed to support long-term athlete development
• Trunk muscles were highlighted as stabilizers that transmit forces between lower and upper limbs in rowing
• The recommendation is qualified with the caveat that further research controlling for training load is needed