Effects of nutrition- and exercise-based performance enhancements in rowing: A network meta-analysis

INTRODUCTION: Previously rowing performance improvements were elicited via numerous different exercise-based approaches like (i) resistance training [1]; (ii) plyometric training [2]; (iii) high-intensity training [3]; (iv) blood flow restriction methods [4]; and (v) various nutritional supplementation strategies [5]. Therefore, network meta-analytical approach was used to examine all those rowing-specific findings within one analysis. Thereby, this network meta-analysis assessed via direct and indirect comparison the occurrence and magnitude of effects following different nutritional supplementation strategies and exercise interventions on acute and chronic rowing performance and its surrogates.
METHODS: PubMed, WebofScience, PsycNet and SPORTDiscus searches were conducted until march 2022 in order to identify studies with the following inclusion criteria: (a) controlled trials, (b) rowing performance and its surrogate parameters as outcomes (c) peer-reviewed published in English. A Frequentistic network meta-analytical approaches were calculated based on standardized mean differences (SMD) using a random effects model.
RESULTS: 71 studies with 1229 healthy rowers (21.5 ± 3.0 years) were included and two networks (acute and chronic) have been created. Both, networks revealed low heterogeneity and non-significant inconsistency (I2 ≤ 35.0% and Q statistics: p ≥ 0.12). Based on P-score rankings, caffeine (P-score 84%; SMD = 0.43) revealed relevantly favorable effects in terms of acute rowing performance enhancement, whilst prior weight reduction (P-score 10%; SMD = -0.48) and extensive preload (P-score 18%; SMD = -0.34) impaired acute rowing performance. Chronic blood flow restriction training (P-score 96%; SMD = 1.26) and the combination of β-hydroxy-β-methylbutyrate and creatine (P-score 91%; SMD = 1.04) induced remarkably large positive effects, while chronic spirulina (P-score 7%; SMD = -1.05) and black currant (P-score 9%; SMD = -0.88) supplementations revealed impairment effects.
CONCLUSION: Homogeneous and consistent findings based on numerous studies indicate that choice of the nutritional supplementation strategy and the exercise training regime is vital for acute and chronic performance enhancement in rowing. While caffeine supplementation increases acute rowing time trial performance, prior weight reduction or extensive preload could impair performance. Furthermore, chronic rowing time trial performance was increased via blood flow restriction training and the combination of β-hydroxy-β-methylbutyrate and creatine supplementation. In contrast chronic spirulina and black currant supplementations might impair chronic rowing performance adaptations.