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Exercise is a front-line intervention to increase functional capacity and reduce pain and disability in people with low strength levels or disorders. However, there is a lack of validated field-based tests to check the initial status and, more importantly, to control the process and make tailored adjustments in load, intensity, and recovery. We aimed to determine the test–retest reliability of a submaximal, resistance-band test to evaluate the strength of the trunk stability muscles using a portable force sensor in middle-aged adults (48 ± 13 years) with medically diagnosed chronic low back pain and healthy peers (n = 35). Participants completed two submaximal progressive tests of two resistance-band exercises (unilateral row and Pallof press), consisting of 5 s maintained contraction, progressively increasing the load. The test stopped when deviation from the initial position by compensation movements occurred. Trunk muscle strength (CORE muscles) was monitored in real time using a portable force sensor (strain gauge). Results revealed that both tests were highly reliable (intra-class correlation [ICC] > 0.901) and presented low errors and coefficients of variation (CV) in both groups. In particular, people with low back pain had errors of 14–19 N (CV = 9–12%) in the unilateral row test and 13–19 N (CV = 8–12%) in the Pallof press. No discomfort or pain was reported during or after the tests. These two easy-to-use and technology-based tests result in a reliable and objective screening tool to evaluate the strength and trunk stability in middle-aged adults with chronic low back pain, considering an error of measurement < 20 N. This contribution may have an impact on improving the individualization and control of rehabilitation or physical training in people with lumbar injuries or disorders. [ABSTRACT FROM AUTHOR]

Purpose: To determine the validity of field-derived mean maximum power (MMP) values for monitoring maximal cycling endurance performance. Methods: Twenty-seven male professional cyclists performed 3 timed trials (TTs) of 1-, 5-, and 20-minute duration that were used as the gold standard reference. Field-based power output data (3336 files; 124 [25] per cyclist) were registered during the preparatory (60 d pre-TT, including training data only) and specific period of the season (60 d post-TT, including both training and competitions). Comparisons were made between TT performance (mean power output) and MMP values obtained for efforts of the same duration as TT (MMP of 1-, 5-, and 20-min duration). The authors also compared TT- and MMP-derived values of critical power (CP) and anaerobic work capacity. Results: A large correlation (P <.001, r >.65) was found between MMP and TT performance regardless of the effort duration or season period. However, considerable differences (P <.05, standard error of measurement [SEM] > 5%) were found between MMP and TT values for all effort durations in the preparatory period, as well as for the derived CP and anaerobic work capacity. Significant differences were also found between MMP and TT of 1 minute in the specific period, as well as for anaerobic work capacity, yet with no differences for MMP of 5- and 20-minute duration or the derived CP (P >.05, SEM < 5%). Conclusion: MMP values (for efforts ≥5 min) and the associated CP obtained from both training sessions and competitions can be considered overall accurate indicators of the cyclist's maximal capabilities, but specific tests might be necessary for shorter efforts or when considering training sessions only. [ABSTRACT FROM AUTHOR]

Purpose: To analyze the feasibility of the 2-point method for estimating ultrasound-derived quadriceps femoris cross-sectional area (QUADACSA). First, (1) the agreement between QUADACSA measured by panoramic ultrasound and magnetic resonance imaging (MRI) was studied, and thereafter, we examined 2 approaches of the 2-point method in terms of (2) estimation errors and (3) test–retest repeatability. Methods: Both thighs of 16 young men were analyzed. Ultrasound-QUADACSA versus MRI-QUADACSA comparison was conducted at 6 thigh lengths (20%–70% of the thigh length). Thereafter, ultrasound-QUADACSA corresponding to 30% and 60% (2-point30%–60%) or 20% and 70% (2-point20%–70%) were used to estimate QUADACSA of the remaining regions. Estimated QUADACSA resulting from both 2-point approaches was compared with the measured one. Finally, the test–retest repeatability was examined by comparing the errors generated on 2 separate estimations. Statistics included the standard error of measurement (SEM) expressed in absolute (in square centimeters) and relative terms (in percentage) as a coefficient of variation (CV), as well as the intraclass correlation cofficient (ICC) and bias. Results: An excellent agreement (ICC ≥ 0.980) and reduced errors (SEM ≤ 2.43 cm2) resulted from the ultrasound-QUADACSA versus MRI-QUADACSA comparison. Although estimation errors found were reduced (CV ≤ 7.50%), they proved to be lower and less biased for the 2-point30%–60%, especially at the central regions (SEM ≤ 2.01 cm2; bias ≤ 0.89 cm2). Similarly, repeatability analysis revealed lower test–retest errors for the 2-point30%–60% (CV ≤ 1.9%) than for the 2-point20%–70% (CV ≤ 4.6%). Conclusion: The 2-point method, especially that implemented using the 30% and 60% regions, represents an accurate and repeatable strategy to evaluate QUADACSA. [ABSTRACT FROM AUTHOR]

We examined the effect of breast cancer surgery and adjuvant therapy on the relationship between bar velocity and relative intensity (load-velocity [L-V] relationship) of the bench press (BP) exercise. Twenty-two breast cancer survivors (age: 48.0±8.2 yr., relative strength: 0.40±0.08) completed a loading test up to the one-repetition maximum (1RM) in the BP using a lightweight carbon bar. General and individual relationships between relative intensity (%1RM) and mean propulsive velocity (MPV) were studied. Furthermore, the mean test velocity (MPVTest) and velocity attained to the 1RM (MPV1RM) were analyzed. These procedures and analyses were also conducted in 22 healthy women (age: 47.8±7.1 yr., relative strength: 0.41±0.09) to examine the differences in velocity parameters derived from these L-V relationships. Polynomial regressions showed very close relationships (R2 ≥0.965) and reduced estimation errors (≤4.9% 1RM) for both groups. Between-group differences in MPV attained to each %1RM were small (≤0.01 m·s−1) and not significant (p≥0.685). Similarly, the MPVTest (0.59±0.06 m·s−1) and MPV1RM (0.17±0.03 m·s−1) were identical for breast cancer survivors and healthy women. These results suggest that practitioners could use the same velocity parameters derived from the BP L-V relationship to prescribe this exercise in middle-aged women, regardless of whether they have suffered from breast cancer. [ABSTRACT FROM AUTHOR]

Purpose: To compare the strength and athletic adaptations induced by 4 programming models. Methods: Fifty-two men were allocated into 1 of the following models: linear programming (intensity increased while intraset volume decreased), undulating programming (intensity and intraset volume were varied in each session or set of sessions), reverse programming (intensity decreased while intraset volume increased), or constant programming (intensity and intraset volume kept constant throughout the training plan). All groups completed a 10-week resistance-training program made up of the free-weight bench press, squat, deadlift, prone bench pull, and shoulder press exercises. The 4 models used the same frequency (2 sessions per week), number of sets (3 per exercise), interset recoveries (4 min), and average intensity throughout the intervention (77.5%). The velocity-based method was used to accurately adjust the planned intensity for each model. Results: The 4 programming models exhibited significant pre–post changes in most strength variables analyzed. When considering the effect sizes for the 5 exercises trained, we observed that the undulating programming (mean effect size = 0.88–2.92) and constant programming (mean effect size = 0.61–1.65) models induced the highest and lowest strength enhancements, respectively. Moreover, the 4 programming models were found to be effective to improve performance during shorter (jump and sprint tests) and longer (upper- and lower-limb Wingate test) anaerobic tasks, with no significant differences between them. Conclusion: The linear, undulating, reverse, and constant programming models are similarly effective to improve strength and athletic performance when they are implemented in a real-context routine. [ABSTRACT FROM AUTHOR]

Purpose: To examine the reproducibility (intradevice and interdevice agreement) of the Rotor 2INpower device under a wide range of cycling conditions. Methods: Twelve highly trained male cyclists and triathletes completed 5 cycling tests, including graded exercise tests at different cadences (70–100 rpm), workloads (100–650 W), pedaling positions (seated and standing), and vibration conditions (20–40 Hz) and an 8-second maximal sprint (>1000 W). An intradevice analysis included a comparison between the power output registered by 3 units of Rotor 2INpower, whereas the power output provided by each one of these units and the gold-standard SRM crankset were compared for the interdevice analysis. Among others, statistical calculations included the standard error of measurement, expressed in absolute (in watts) and relative terms as the coefficient of variation (CV). Results: Except for the graded exercise test seated at 100 rpm/100 W (CV = 10.2%), the intradevice analysis showed an acceptable magnitude of error (CV ≤ 6.9%, standard error of measurement ≤ 12.3 W) between the 3 Rotor 2INpower. Similarly, these 3 units showed an acceptable agreement with the gold standard in all graded exercise test situations (CV ≤ 4.0%, standard error of measurement ≤ 13.1 W). On the other hand, both the intradevice and interdevice agreements proved to be slightly reduced under high cadences (intradevice: CV ≤ 10.2%; interdevice: CV ≤ 4.0%) and vibration (intradevice: CV ≤ 4.0%; interdevice: CV ≤ 3.6%), as well as during standing pedaling (intradevice: CV ≤ 4.1%; interdevice: CV ≤ 2.5%). Although within the limits of an acceptable agreement, measurement errors increased during the sprint tests (CV ≤ 7.4%). Conclusions: Based on these results, the Rotor 2INpower could be considered a reproducible tool to monitor power output in most cycling situations. [ABSTRACT FROM AUTHOR]

Purpose: A variation of the traditional squat (SQ) rebound technique (REBOUND) including a momentary pause ∼2 seconds (PAUSE) between eccentric and concentric phases has been proposed. Although there is a consensus about the lower acute effects on performance of this PAUSE variant compared with traditional REBOUND technique, no information exists about the differences in longitudinal adaptations of these SQ executions. Methods: A total of 26 men were randomly assigned into the PAUSE (n = 13) or REBOUND (n = 13) groups and completed a 10-week velocity-based training using the SQ exercise, only differing in the technique. Neuromuscular adaptations were assessed by the changes in the 1-repetition maximum strength and mean propulsive velocity achieved against the absolute loads (in kilograms) common to pretest and posttest. Functional performance was evaluated by the following tests: countermovement jump, Wingate, and sprint time at 0 to 10, 10 to 20, and 0 to 20 m. Results: Whereas both groups showed significant increases in most of the neuromuscular tests (P <.05), the PAUSE (effect size [ES] = 0.76–1.12) presented greater enhancements than REBOUND (ES = 0.45–0.92). Although not significant, improvements in Wingate and sprint time at 0 to 10 and 0 to 20 m were higher for PAUSE (ES = 0.31–0.46) compared with REBOUND (ES = 0.10–0.29). Conversely, changes on countermovement jump and sprint time at 10 to 20 m were superior for REBOUND (ES = 0.17–0.88) than for PAUSE (ES = 0.09–0.75). Conclusion: Imposing a pause between eccentric and concentric phases in the SQ exercise could be an interesting strategy to increase neuromuscular and functional adaptations in sport actions that mainly depend on concentric contractions. Moreover, sport abilities highly dependent on the stretch-shortening cycle could benefit from the REBOUND or a combination of the 2 techniques. [ABSTRACT FROM AUTHOR]

Background: Although the superior effectiveness of free‐weight over machine‐based training has been a traditionally widespread assumption, longitudinal studies comparing these training modalities were scarce and heterogeneous. Objective: This research used the velocity‐based method to compare the effects of free‐weight and machine‐based resistance training on athletic performance and muscle architecture. Methods: Thirty‐four resistance‐trained men participated in an 8‐week resistance training program allocated into free‐weight (n = 17) or machine‐based (n = 17) groups. Training variables (intensity, intraset fatigue, and recovery) were identical for both groups, so they only differed in the use of a barbell or specific machines to execute the full squat, bench press, prone bench pull, and shoulder press exercises. The velocity‐based method was implemented to accurately adjust the planned intensity. Analysis of covariance and effect size (ES) statistics were used to compare both training modalities on a comprehensive set of athletic and muscle architecture parameters. Results: No between‐group differences were found for any athletic (p ≥ 0.146) and muscle architecture (p ≥ 0.184) variable. Both training modalities significantly and similarly improved vertical jump (Free‐weight: ES ≥ 0.45, p ≤ 0.001; Machine‐based: ES ≥ 0.41, p ≤ 0.001) and lower limb anaerobic capacity (Free‐weight: ES ≥ 0.39, p ≤ 0.007; Machine‐based: ES ≥ 0.31, p ≤ 0.003). Additionally, the machine‐based group meaningfully enhanced upper limb anaerobic power (ES = 0.41, p = 0.021), whereas the free‐weight group significantly improved the change of direction (ES = ‐0.54, p = 0.003) and 2/6 balance conditions analyzed (p ≤ 0.012). Changes in sprint capacity (ES ≥ ‐0.13, p ≥ 0.274), fascicle length, and pennation angle (ES ≤ 0.19, p ≥ 0.129) were not significant for either training modality. Conclusion: Adaptations in athletic performance and muscle architecture would not be meaningfully influenced by the resistance modality trained. [ABSTRACT FROM AUTHOR]

Objectives: (1) To describe the fast Fourier transform (FFT) multijoint as monopodal postural stability measurement in well-trained athletes, (2) to compare the within-subject FFT between laterality, joints, and body segments, and (3) to establish the within- and between-subject relationship between joints. Methods: Twelve national-level basketball players participated voluntarily in this investigation. The participants performed two 60-second repetitions of a monopodal stability test (1 repetition with each lower limb), separated by 3 minutes of active recovery. All tests were recorded by 4 WIMU PRO™ inertial devices located on the ankle, knee, lumbar spine, and thoracic spine. The main variable was total acceleration, where the FFT was applied. Results: The higher instability results were found in the ankle and in the nondominant lower limb (dominant = 1.131 [0.122] a.u. (arbitrary units); nondominant = 1.141 [0.172] a.u). In the body segment analysis, the greater percentage of differences (%diff) were shown between lumbar spine and knee in the dominant (%diff = −2.989%; d = 0.87) and nondominant (%diff = −3.243%; d = 0.90) lower limb. Finally, very large between-subjects variability was found in all joints and body segments. Conclusions: The described protocol is proposed for monopodal postural stability assessment, being useful to provide information about the stability of joints and the body segment between joints. Besides, a within-subject analysis is recommended, and the FFT calculation will enable a linear analysis of each test. [ABSTRACT FROM AUTHOR]

Supplemental Digital Content is Available in the Text. Since 2010, the velocity-based approach (VBT) has been established as a reliable method to be used during resistance training (RT) interventions. VBT lies in the monitoring of the barbell velocity during the concentric phase of an exercise, which is a direct consequence of the force applied by the athlete to the external load. VBT offers coaches and physical trainers of soccer teams a wide spectrum of practical applications. Considering the close association between the barbell velocity and the relative intensity (i.e., load-velocity relationship), practitioners could ensure "on the go" that players train very close to the programmed load in each training set. Methodologies derived from the VBT, such as the velocity loss or the "level of effort," allow to plan and control the intraset fatigue to be incurred by the soccer players during RT. Incorporating the barbell velocity monitoring into the testing routine would permit the determination of the changes in strength across the entire spectrum of loads and offer a valid and practical proposal to evaluate the neuromuscular recovery status. The current article aimed to review in-depth the above-mentioned practical applications and some technological and technical aspects to consider when implementing the VBT in soccer. [ABSTRACT FROM AUTHOR]

Hernández-Belmonte, A, Courel-Ibáñez, J, Conesa-Ros, E, Martínez-Cava, A, and Pallarés, JG. Level of effort: A reliable and practical alternative to the velocity-based approach for monitoring resistance training. J Strength Cond Res 36(11): 2992–2999, 2022—This study analyzed the potential of the level of effort methodology as an accurate indicator of the programmed relative load (percentage of one-repetition maximum [%1RM]) and intraset volume of the set during resistance training in the bench press, full squat, shoulder press, and prone bench pull exercises, through 3 specific objectives: (a) to examine the intersubject and intrasubject variability in the number of repetitions to failure (n RM) against the actual %1RM lifted (adjusted by the individual velocity), (b) to investigate the relationship between the number of repetitions completed and velocity loss reached, and (c) to study the influence of the subject's strength level on the aforementioned parameters. After determining their individual load-velocity relationships, 30 subjects with low (n = 10), medium (n = 10), and high (n = 10) relative strength levels completed 2 rounds of n RM tests against their 65, 75, 85, and 95% 1RM in the 4 exercises. The velocity of all repetitions was monitored using a linear transducer. Intersubject and intrasubject variability analyses included the 95% confidence intervals (CIs) and the the standard error of measurement (SEM), respectively. Coefficient of determination (R2) was used as the indicator of relationship. n RM showed a limited intersubject (CI ≤ 4 repetitions) and a very low intrasubject (SEM ≤1.9 repetitions) variability for all the strength levels, %1RM, and exercises analyzed. A very close relationship (R 2 ≥ 0.97) between the number of repetitions completed and the percentage of velocity loss reached (from 10 to 60%) was found. These findings strengthen the level of effort as a reliable, precise, and practical strategy for programming resistance training. [ABSTRACT FROM AUTHOR]

This study aimed to analyse the (i) concurrent validity, (ii) inter-unit reliability, and (iii) biological variability of a low-cost device called Pocket radar. Eleven men recreational soccer players performed 6 kicks to a soccer ball, whereas 13 men recreational tennis players conducted 10 shots to a tennis ball. All executions were simultaneously measured by two Pocket units and the Stalker radar (reference criterion). The withinsubject variation among the executions was used for the biological variability analysis. The level of agreement and magnitude of errors included the intraclass correlation coefficient (ICC), Pearson's correlation coefficient (r), bias, and the smallest detectable change (SDC). A good agreement (ICC = 0.98, r = 0.98) and very low magnitude of error (SDC = 7.70 km·h-1, bias = 3.19 km·h-1) were found between both Pocket units and the Stalker, in soccer and tennis. Inter-unit analysis found limited technical errors (SDC = 5.49 km·h-1, bias = -0.93 km·h-1) and nearly perfect agreement (ICC = 0.99, r = 0.98) in both sessions. These technical errors were lower than the variations due to the biological variability, in soccer (SDC = 2.47 km·h-1 vs. SDC = 8.6 km·h-1) and tennis (SDC = 5.49 km·h-1 vs. SDC = 21.95 km·h-1). These findings suggest the Pocket radar as a valid and highly sensitive tool for BV measurement. [ABSTRACT FROM AUTHOR]

Training prescription in running activities have benefited from power output (PW) data obtained by new technologies. Nevertheless, to date, the suitability of PW data provided by these tools is still uncertain. The present study aimed to: (i) analyze the repeatability of five commercially available technologies for running PW estimation, and (ii) examine the concurrent validity through the relationship between each technology PW and oxygen uptake (VO2). On two occasions (test-retest), twelve endurance-trained male athletes performed on a treadmill (indoor) and an athletic track (outdoor) three submaximal running protocols with manipulations in speed, body weight and slope. PW was simultaneously registered by the commercial technologies StrydApp, StrydWatch, RunScribe, GarminRP and PolarV, while VO2 was monitored by a metabolic cart. Test-retest data from the environments (indoor and outdoor) and conditions (speed, body weight and slope) were used for repeatability analysis, which included the standard error of measurement (SEM), coefficient of variation (CV) and intraclass correlation coefficient (ICC). A linear regression analysis and the standard error of estimate (SEE) were used to examine the relationship between PW and VO2. Stryd device was found as the most repeatable technology for all environments and conditions (SEM ≤ 12.5 W, CV ≤ 4.3%, ICC ≥ 0.980), besides the best concurrent validity to the VO2 (r ≥ 0.911, SEE ≤ 7.3%). On the contrary, although the PolarV, GarminRP and RunScribe technologies maintain a certain relationship with VO2, their low repeatability questions their suitability. The Stryd can be considered as the most recommended tool, among the analyzed, for PW measurement. [ABSTRACT FROM AUTHOR]