Strength and Power Testing of Athletes: A Multicenter Study of Test-Retest Reliability

Do Strength and Anthropometric Size of the Lower Body Correlate with Serum Testosterone Levels?

PURPOSE

Although lower body strength and size are often regarded as symbols of masculinity, their relationship to testosterone is unclear. This study aimed to determine the correlation between lower body strength, size, and testosterone levels.

MATERIALS AND METHODS

Serum testosterone levels, waist circumference, and body mass index (BMI) were measured in 69 men with erectile dysfunction (age >40 years). The circumferences of the thigh and calf were measured, and the muscle strength of the knee joints was evaluated using an isokinetic dynamometer. Patients were classified into three groups according to testosterone levels (group 1, <230 ng/dL; group 2, 230 to 350 ng/dL; group 3, >350 ng/dL). Differences in calf and thigh circumference, bilateral knee extension, and flexion strength between the three groups were investigated using a one-way analysis of variance. Pearson's chi-square test was used to assess differences in lifestyle habits and underlying diseases. A partial correlation analysis was conducted to determine the association between testosterone levels and lower body size and strength.

RESULTS

There was no difference in BMI among the three groups, but waist circumference was significantly larger in group 1 than in groups 2 and 3. When comparing weight-adjusted values, bilateral thigh circumference showed a significant difference among the three groups. There was also a significant difference between the three groups in the weight-adjusted left calf circumference and in the weight-adjusted right knee extension strength. The partial correlation test showed a significant positive correlation between thigh and calf circumference values adjusted for weight and serum testosterone levels. Weight-adjusted knee extension strength demonstrated a significant positive correlation with serum testosterone levels.

CONCLUSIONS

Weight-adjusted thigh and calf circumferences, along with the thigh-to-waist ratio, showed a positive correlation with testosterone levels. Weight-adjusted knee extension strength was positively correlated with testosterone levels. Therefore, a robust thigh and strong lower body are related to testosterone.

Assessing the individual relationships between physical test improvements and external load match parameters in male professional football players-a brief report

Purpose

This study aimed to explore whether a meaningful improvement in physical performance following an in-season strength training intervention can be related to external load match parameters at an individual level in professional male football players.

Methods

Eight male professional football players (25.4 ± 3.1 years, 184.1 ± 3.4 cm, 79.3 ± 2.2 kg) completed a 10-week strength intervention period in addition to football-specific training and matches. Commonly used physical and external load measures were assessed before and after intervention. Physical performance improvements had to exceed the measurement's typical error and the smallest worthwhile difference (SWD) to be considered meaningful. External load match parameters were assessed before and after the intervention period using SWD and non-overlap of all pairs (NAP) analysis. A Bayesian pairwise correlation analysis was performed to evaluate relationships between changes in physical performance and external load match parameters.

Results

Three players displayed meaningful improvements in two to five physical performance measures. However, positive changes exceeding the SWD and positive effects in NAP results were observed for all players in external load match parameters. Kendall's tau correlation analysis showed evidence (base factor >3) for only one correlation (maximum speed - decelerations, τ = -0.62) between the changes in physical performance and external load measures, while the remaining comparisons exhibited no relation.

Conclusions

The findings suggest that improvements in physical performance may not necessarily translate to improvements in external load match parameters. Further research, with larger sample sizes, is needed to understand potential mechanisms between acute and chronic physical performance changes and football external load parameters during training and matches.

Reliability of Measures of Lower-Body Strength and Speed in Academy Male Adolescent Soccer Players

ABSTRACT

Ferguson, J, Gibson, NV, Weston, M, and McCunn, R. Reliability of measures of lower body strength and speed in academy male adolescent soccer players. J Strength Cond Res 38(3): e96-e103, 2024-The Nordbord and ForceFrame represent a practical and time efficient means of assessing eccentric hamstring and isometric adductor strength in the large number of squads and players associated with youth soccer academies, yet measurement reliability in this population is unexamined. Therefore, over a period of 4 days, with no less than 24 hours and no more than 48 hours between trials, 37 players (age: 14.7 ± 0.8 years, stature: 168.7 ± 7.8 cm, mass: 57.7 ± 9.1 kg, and maturity offset: 0.8 ± 0.9 years) were assessed for eccentric hamstring strength (force, torque), isometric adductor strength (long and short lever positions), and 30-m sprint (5, 10, and 20-m splits), using the Nordbord, ForceFrame, and electronic timing gates, respectively, on 3 separate occasions. Relative reliability (intraclass correlation coefficient) was rated as good for all Nordbord (range: 0.86-0.89) and ForceFrame (0.78-0.85) measures and ranged from moderate (0.53) to excellent (0.93) for the speed measures, improving with increased distance. Absolute reliability (standard error of the measurement [%SEM]) ranged from 7 to 8% (Nordbord), 3 to 11% (ForceFrame), and 1 to 4% (sprints). Our data provide the first Nordbord and ForceFrame reliability estimates in adolescent soccer academy players. To interpret test sensitivity, practitioners are encouraged to interpret our estimates of absolute reliability against meaningful change values derived from personal experience and evidence-based knowledge and not against absolute or standardized thresholds.

Monitoring Changes in Lower-Limb Strength and Power in Elite Athletes With the Countermovement-Jump and Keiser Leg-Press Tests

PURPOSE

To determine the utility of countermovement-jump and Keiser leg-press tests for tracking changes in elite athletes of different sports.

METHODS

Elite athletes of the Norwegian Olympic Federation (126 individuals from 18 sports) performed countermovement-jump and Keiser tests on 2 to 11 occasions between 2014 and 2021. Separate analyses were performed for male and female alpine skiing, male and female handball, male ice hockey, and males and females of other sports. Means and standard deviations of consecutive change scores were combined with short-term error of measurement (3.7%-7.0%) and smallest important changes (2.0%-3.6%, defined by standardization) to determine the proportions of athletes who experienced decisive changes in 2 senses: first, the athlete did not get substantially worse or better (>90% chance of either), and second, the athlete did get substantially worse or better (>90% chance of either).

RESULTS

Averaged over sports, Keiser peak power and relative peak power had the highest proportions of decisive changes in the first (60% and 55%) and second senses (25% and 28%). The velocity intercept of the force-velocity relationship had the lowest proportions in the first and second senses (29% and 11%), while jump height, Keiser mean power, relative mean power, the force intercept, and the slope of the force-velocity relationship had similar proportions (40%-53% and 15%-21%).

CONCLUSIONS

With the possible exception of the Keiser test velocity intercept, the proportions of observed decisive changes in elite athletes using Keiser measures and countermovement-jump height between tests appear adequate for the measures to be useful for routine monitoring.

The effects of being told you are in the intervention group on training results: a pilot study

Little is known about the placebo effects when comparing training interventions. Consequently, we investigated whether subjects being told they are in the intervention group get better training results compared to subjects being told they are in a control group. Forty athletes (male: n = 31, female: n = 9) completed a 10-week training intervention (age: 22 ± 4 years, height: 183 ± 10 cm, and body mass: 84 ± 15 kg). After randomization, the participants were either told that the training program they got was individualized based on their force-velocity profile (Placebo), or that they were in the control group (Control). However, both groups were doing the same workouts. Measurements included countermovement jump (CMJ), 20-m sprint, one-repetition maximum (1RM) back-squat, a leg-press test, ultrasonography of muscle-thickness (m. rectus femoris), and a questionnaire (Stanford Expectations of Treatment Scale) (Younger et al. in Clin Trials 9(6):767-776, 2012). Placebo increased 1RM squat more than Control (5.7 ± 6.4% vs 0.9 ± 6.9%, [0.26 vs 0.02 Effect Size], Bayes Factor: 5.1 [BF₁₀], p = 0.025). Placebo had slightly higher adherence compared to control (82 ± 18% vs 72 ± 13%, BF₁₀: 2.0, p = 0.08). Importantly, the difference in the 1RM squat was significant after controlling for adherence (p = 0.013). No significant differences were observed in the other measurements. The results suggest that the placebo effect may be meaningful in sports and exercise training interventions. It is possible that ineffective training interventions will go unquestioned in the absence of placebo-controlled trials.

Association Between Physical Performance Tests and External Load During Scrimmages in Highly Trained Youth Ice Hockey Players

PURPOSE

To investigate the relationship between physical performance tests and on-ice external load from simulated games (scrimmages) in ice hockey.

METHODS

A total of 14 players completed a physical performance test battery consisting of 30-m sprint test-run and 30-m sprint test-skate (including 10-m split times and maximum speed), countermovement jump, standing long jump, bench press, pull-ups, and trap bar deadlift and participated in 4 scrimmages. External load variables from scrimmages included total distance; peak speed; slow (< 11.0 km/h), moderate (11.0-16.9 km/h), high (17.0-23.9 km/h), and sprint (> 24.0 km/h) speed skating distance; number of sprints; PlayerLoad™; number of high-intensity events (> 2.5 m/s); accelerations; decelerations; and changes of direction. Bayesian pairwise correlation analyses were performed to assess the relationship between physical performance tests and external load performance variables.

RESULTS

The results showed strong evidence (Bayes factor > 10) for associations between pull-ups and high-intensity events (τ = .61) and between maximum speed skate and peak speed (τ = .55). There was moderate evidence (Bayes factor >3 to <10) for 6 associations: both maximum speed skate (τ = .44) and countermovement jump (τ = .44) with sprint speed skating distance, countermovement jump with number of sprints (τ = .46), pull-ups with changes of direction (τ = .50), trap bar with peak speed (τ = .45), and body mass with total distance (τ = .49).

CONCLUSION

This study found physical performance tests to be associated with some of the external load variables from scrimmages. Nevertheless, the majority of correlations did not display meaningful associations, possibly being influenced by the selection of physical performance tests.

Effects of Low- Versus High-Velocity-Loss Thresholds With Similar Training Volume on Maximal Strength and Hypertrophy in Highly Trained Individuals

AIMS

In the present intervention study, low-velocity-loss (LVL) versus high-velocity-loss (HVL) thresholds in the squat and bench press were compared for changes in muscle strength, power, and hypertrophy.

METHODS

Strength-trained volunteers (7♀ and 9♂; age: 27.2 [3.4] y; height: 174.6 [8.0] cm; body mass: 75.3 [10.1] kg) were randomized into an LVL or HVL threshold group (LVL n = 3♀ + 5♂, and HVL n = 4♀ + 4♂). Training took place 3 times per week over 6 weeks (loads: ∼75%-90% of 1-repetition maximum [1RM]). The thresholds of LVLs and HVLs were set at 20% and 40% of maximal velocity, respectively, for the squat, and at 30% and 60%, respectively, for the bench press. Before and after the intervention, 1RM, leg press power, and squat jump were tested. The load (∼45% of 1RM) corresponding to 1-m/s velocity was assessed in all sessions for both exercises. In addition, the thickness of the vastus lateralis and triceps brachii and body composition (dual-energy X-ray absorptiometry [DEXA]) were measured.

RESULTS

Squat and bench-press 1RM increased similarly in both groups by 7% to 11% (SD: 4%-6%, P < .05). No group differences were observed for changes in jump height, leg press power, or DEXA lean mass. However, HVL showed a small increase in muscle thickness of the vastus lateralis compared with LVL (6 ± 6% [95% CI] group difference, P < .05).

CONCLUSION

For strength-trained individuals, high-volume lower-velocity-loss thresholds were as effective as higher thresholds for improvements in 1RM strength; but local hypertrophy was seemingly elicited faster with higher velocity-loss thresholds.

COVID-19 and athletes: Endurance sport and activity resilience study-CAESAR study

Background: The COVID-19 pandemic and imposed restrictions influenced athletic societies, although current knowledge about mild COVID-19 consequences on cardiopulmonary and physiologic parameters remains inconclusive. This study aimed to assess the impact of mild COVID-19 inflection on cardiopulmonary exercise test (CPET) performance among endurance athletes (EA) with varied fitness level. Materials and Methods: 49 EA (n_male = 43, n_female = 6, mean age = 39.94 ± 7.80 yr, height = 178.45 cm, weight = 76.62 kg; BMI = 24.03 kgm^-2) underwent double treadmill or cycle ergometer CPET and body analysis (BA) pre- and post-mild COVID-19 infection. Mild infection was defined as: (1) without hospitalization and (2) without prolonged health complications lasting for >14 days. Speed, power, heart rate (HR), oxygen uptake (VO₂), pulmonary ventilation, blood lactate concentration (at the anaerobic threshold (AT)), respiratory compensation point (RCP), and maximum exertion were measured before and after COVID-19 infection. Pearson's and Spearman's r correlation coefficients and Student t-test were applied to assess relationship between physiologic or exercise variables and time. Results: The anthropometric measurements did not differ significantly before and after COVID-19. There was a significant reduction in VO₂ at the AT and RCP (both p < 0.001). Pre-COVID-19 VO₂ was 34.97 ± 6.43 ml kg·min^-1, 43.88 ± 7.31 ml kg·min^-1 and 47.81 ± 7.81 ml kg·min^-1 respectively for AT, RCP and maximal and post-COVID-19 VO₂ was 32.35 ± 5.93 ml kg·min^-1, 40.49 ± 6.63 ml kg·min^-1 and 44.97 ± 7.00 ml kg·min^-1 respectively for AT, RCP and maximal. Differences of HR at AT (p < 0.001) and RCP (p < 0.001) was observed. The HR before infection was 145.08 ± 10.82 bpm for AT and 168.78 ± 9.01 bpm for RCP and HR after infection was 141.12 ± 9.99 bpm for AT and 165.14 ± 9.74 bpm for RCP. Time-adjusted measures showed significance for body fat (r = 0.46, p < 0.001), fat mass (r = 0.33, p = 0.020), cycling power at the AT (r = -0.29, p = 0.045), and HR at RCP (r = -0.30, p = 0.036). Conclusion: A mild COVID-19 infection resulted in a decrease in EA's CPET performance. The most significant changes were observed for VO₂ and HR. Medical Professionals and Training Specialists should be aware of the consequences of a mild COVID-19 infection in order to recommend optimal therapeutic methods and properly adjust the intensity of training.

Strength and Power Testing of Athletes: Associations of Common Assessments Over Time

PURPOSE

This study examined the associations among common assessments for measuring strength and power in the lower body of high-performing athletes, including both cross-sectional and longitudinal data.

METHODS

A total of 100 participants, including both male (n = 83) and female (n = 17) athletes (21 [4] y, 182 [9] cm, 78 [12] kg), were recruited for the study using a multicenter approach. The participants underwent physical testing 4 times. The first 2 sessions (1 and 2) were separated by ∼1 week, followed by a period of 2 to 6 months, whereas the last 2 sessions (3 and 4) were also separated by ∼1 week. The test protocol consisted of squat jumps, countermovement jumps, jump and reach, 30-m sprint, 1-repetition-maximum squat, sprint cycling, and a leg-press test.

RESULTS

There were generally acceptable correlations among all performance measures. Variables from the countermovement jumps and leg-press power correlated strongly with all performance assessments (r = .52-.79), while variables from sprint running and squat-jump power displayed more incoherent correlations (r = .21-.82). For changes over time, the correlations were mostly strong, albeit systematically weaker than for cross-sectional measures.

CONCLUSIONS

The associations observed among the performance assessments seem to be consistent for both cross-sectional data and longitudinal change scores. The weaker correlations for change scores are most likely mainly caused by lower between-subjects variations in the change scores than for the cross-sectional data. The present study provides novel information, helping researchers and practitioners to better interpret the relationships across common performance assessment methods.