The Influence of Lower Extremity Lean Mass on Landing Biomechanics During Prolonged Exercise

Fat-Free Mass Index in Sport: Normative Profiles and Applications for Collegiate Athletes

ABSTRACT

Jagim, AR, Harty, PS, Jones, MT, Fields, JB, Magee, M, Smith-Ryan, AE, Luedke, J, and Kerksick, CM. Fat-free mass index in sport: normative profiles and applications for collegiate athletes. J Strength Cond Res 38(9): 1687-1693, 2024-Recent concerns have been raised regarding the ethical considerations of conducting body composition assessments in sports. Specific apprehensions pertain to the inappropriate use of percent body fat and the limited application of the results to performance and recovery. Fat-free mass index (FFMI), a height-adjusted assessment of FFM, can serve as an alternative body composition metric to focus on in sports. Fat-free mass index provides valuable context regarding an optimal amount of FFM, accounting for skeletal frame and height while helping to qualify an athlete's FFM as low, moderate, or high. This review posits that shifting the focus of body composition measures to FFM can support more ideal targets across athletic seasons, careers, and the return to play after injury. In addition, a FFM focus may help change the perception of body composition assessment and how athletes perceive their current body because of the increased focus on the FFM compartment and the goal of maximizing tissue accrual, rather than focusing on fat loss. Fat-free mass index is calculated by dividing FFM (kg) by height (m 2 ) and can serve to normalize FFM, relative to height, and enable comparisons across athletes, sport types, and sex. Previous research has identified differences in FFMI across sex and among sport categories. Still, there is a need for more published data to develop optimal ranges for FFMI across sex, sports, and positions. As more data become available, FFMI has the potential to provide normative guidelines for optimal FFM development, performance, and injury risk reduction. The purpose of the current review was to summarize FFMI values across collegiate sport categories and competitive status to provide normative profiles, according to sex and sport type.

Comparison of different periodization models on isotonic and isokinetic muscle strength and lean mass in tactical athletes

INTRODUCTION

Tactical athletes need to develop strength and lower limb lean mass (LL LM) to perform effectively. Resistance training (RT) is the most effective way to achieve these goals. Two periodization models stand out: traditional linear periodization (TLP) and daily undulating periodization (DUP).

OBJECTIVE

To verify the effect of lower limb RT with TLP and DUP on isotonic and isokinetic muscle strength and lean mass in tactical athletes.

METHOD

Thirty-five Brazilian Army military (21.57 ± 2.02 years; 81.81 ± 11.19 Kg; 177.79 ± 6.88 cm) were divided into two treatment groups and one active control group.

INTERVENTIONS

The treatment groups performed 9 weeks of supervised RT (18 sessions), consisting of free weight exercises in this order: back squat, squat lunge, deadlift, and stiff legged deadlift. Dynamic isotonic muscle strength, lean mass, and isokinetic knee extension and flexion were assessed at baseline and post treatment period.

RESULTS

There was a significant pre-post difference in dynamic isotonic muscle strength (TLP, P < 0.001; DUP, P < 0.001) and lean mass (TLP, P = 0.034; DUP, P = 0.003) of LL LM in both treatment groups. However, effect sizes (ES) and variations (%Δ) of gains were greater in the DUP group both in muscle strength (TLP, ES = 1.55, %Δ = 30.97; DUP, ES = 2.55, %Δ = 36.02), and in lean mass (TLP, ES = 0.13, %Δ = 2.07; DUP, ES = 0.44, %Δ = 2.95). For isokinetic knee flexion strength, a significant difference was found between the TLP versus CON.

CONCLUSION

Both lower limb RT periodization models provided gains in muscle strength and lean mass, with a small advantage for the DUP approach. In the isokinetic knee flexion strength, the TLP was more effective.

Dietary Intake and Energy Expenditure During Two Different Phases of Athletic Training in Female Collegiate Lacrosse Players

Kumahara, H, Ohta, C, Nabeshima, E, Nakayama, A, Mine, S, and Yamato, T. Dietary intake and energy expenditure during two different phases of athletic training in female collegiate lacrosse players. J Strength Cond Res 34(6): 1547-1554, 2020-This study aims to investigate the state of nutrient intake and energy expenditure (EE) among various phases of periodization in female collegiate lacrosse players. A total of 17 Japanese female collegiate lacrosse players (age: 20.0 ± 0.9 years) were enrolled in this study. Physical activity (PA) and dietary intake were assessed over each 1-week period during the training preparatory phase (P-phase) and transition phase (T-phase). The exercise training-related EE (EEE) and EE associated with other daily living activities (i.e., nonexercise activity thermogenesis [NEAT]), were measured using accelerometers and heart rate (HR) monitoring using the flex-HR method. The total daily EE during the P-phase was significantly higher than that of the T-phase (2,168 ± 248 vs. 1744 ± 138 kcal·d; p < 0.01); however, no significant differences were observed in the total energy intake. Moreover, EEE during the P-phase was significantly higher than that of the T-phase, whereas no significant difference was found in NEAT. Furthermore, no significant differences were noted in any macronutrient intake variable observed between the 2 phases (protein:fat:carbohydrate ratio: 12.6 ± 1.5:32.9 ± 3.9:54.1 ± 5.1% in the P-phase vs. 12.1 ± 1.7:30.7 ± 3.9:55.7 ± 5.2% in the T-phase). The carbohydrate and protein intake were below recommended levels during the P-phase. Conversely, the saturated fatty acid ratio was higher than the dietary goals for disease prevention. Based on the changes in the PA volume observed during different training phases, female collegiate lacrosse players did not attain optimal nutrient intake required for optimal athletic performance and health.

BIOMECHANICAL EFFECTS OF HYPERPRONATION ON MULTIDIRECTIONAL ANKLE ANGULAR DISPLACEMENT AND STIFFNESS

Hyperpronation of the foot is believed to contribute to ankle hypermobility and associated stiffness reduction, but the underlying biomechanical mechanisms remain unknown. This study aimsed to investigate multidirectional ankle displacement and associated stiffness when a posterior–anterior impact force was applied to the posterior knee compartment. Forty healthy adults with and without foot hyperpronation were recruited. A three-dimensional motion capture system and force plates were used to acquire angular displacement and ankle joint moment data. The independent [Formula: see text]-test and Mann–Whitney [Formula: see text] test were used to compare the group differences in ankle angular displacement, moment, and stiffness. Spearman’s rho test was performed to determine the relationship between ankle angular displacement and stiffness. The hyperpronation group demonstrated significantly greater sagittal ([Formula: see text]) and frontal plane ([Formula: see text]) angular displacements and reduced sagittal plane ankle stiffness ([Formula: see text]) than the neutral group. The Spearman’s correlation analysis showed a close inverse relationship between the ankle angular displacement and stiffness, ranging from [Formula: see text] to [Formula: see text]. The biomechanical data in our study suggest that individuals with foot hyperpronation present with multidirectional hypermobility and a reduction in ankle stiffness. These factors contribute to an increased risk of ankle-foot injury in individuals with foot hyperpronation.

Structural and functional body components in athletic health and performance phenotypes

Advances in body composition assessment enable a detailed body composition analyses and the respective organization at different levels. Sports-related professionals are interested in understanding how and which body components are relevant for improving performance, prevent injury risk, and monitor athletic health. The aim of this review is to propose an integrative model that links performance, injury risk, and athletic health with body components, and to report their cross-sectional and longitudinal associations. Cross-sectional studies reveal that endurance athletes with higher fat mass (FM) show a longer race time, whereas a higher fat-free mass benefits power and strength-related tasks. Longitudinal studies indicated that increases in intracellular water, assessed through dilution techniques, were associated with power and strength improvements, independently of weight and lean-soft-tissue changes. There is evidence that athletes involved in weight-sensitive sports restrict energy intake, thus reducing energy availability (EA) and compromising bone health (Female Athlete Triad). To counteract the low EA and related negative energy balance, metabolic adaption (MA) occurs to promote energy conservation. Currently, reference values for body composition assessment using anthropometry and DXA are available for a few sports, according to sex. More research is needed to develop a functional body composition profile according to sports-specific requirements.