Person: Hernández Belmonte, Alejandro
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The 2-point method: A quick, accurate, and repeatable approach to estimate ultrasoundderived quadriceps femoris cross-sectional area
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.
Velocity-based method in free-weight and machine-based training modalities: the degree of freedom matters
This study aimed to analyze and compare the load-velocity relationships of free-weight and machine-based modalities of 4 resistance exercises. Moreover, we examined the influence of the subject's strength level on these load-velocity relationships. Fifty men completed a loading test in the free-weight and machine-based modalities of the bench press, full squat, shoulder press, and prone bench pull exercises. General and individual relationships between relative intensity (%1RM) and velocity variables were studied through the coefficient of determination (R2) and standard error of the estimate (SEE). Moreover, the velocity attained to each %1RM was compared between both modalities. Subjects were divided into stronger and weaker to study whether the subject's strength level influences the mean test (mean propulsive velocity [MPVTest]) and 1RM (MPV1RM) velocities. For both modalities, very close relationships (R2 ≥ 0.95) and reduced estimation errors were found when velocity was analyzed as a dependent (SEE ≤ 0.086 m·s−1) and independent (SEE ≤ 5.7% 1RM) variable concerning the %1RM. Fits were found to be higher (R2 ≥ 0.995) for individual load-velocity relationships. Concerning the between-modality comparison, the velocity attained at each intensity (from 30 to 100% 1RM) was significantly faster for the free-weight variant. Finally, nonsignificant differences were found when comparing MPVTest (differences ≤ 0.02 m·s−1) and MPV1RM (differences ≤ 0.01 m·s−1) between stronger and weaker subjects. These findings prove the accuracy and stability of the velocity-based method in the free-weight and machine-based variants but highlight the need to use the load-velocity relationship (preferably the individual one) specific to each training modality.
Carácter del esfuerzo como metodología para la prescripción y monitorización del entrenamiento de fuerza: Fundamentación, hallazgos y futuras líneas
Effects of velocity loss threshold during resistance training on strength and athletic adaptations: a systematic review with meta-analysis
This study aimed to systematically review the effects of the different velocity loss (VL) thresholds during resistance training (RT) on strength and athletic adaptations. The VL was analyzed as both a categorical and continuous variable. For the categorical analysis, individual VL thresholds were divided into Low-ModVL (≤ 25% VL) or Mod-HighVL (> 25% VL). The efficacy of these VL thresholds was examined using between-group (Low-ModVL vs. Mod-HighVL) and within-group (pre–post effects in each group) analyses. For the continuous analysis, the relationship (R2) between each individual VL threshold and its respective effect size (ES) in each outcome was examined. Ten studies (308 resistance-trained young men) were finally included. The Low-ModVL group trained using a significantly (p ≤ 0.001) lower VL (16.1 ± 6.2 vs. 39.8 ± 9.0%) and volume (212.0 ± 102.3 vs. 384.0 ± 95.0 repetitions) compared with Mod-HighVL. Between-group analyses yielded higher efficacy of Low-ModVL over Mod-HighVL to increase performance against low (ES = 0.31, p = 0.01) and moderate/high loads (ES = 0.21, p = 0.07). Within-group analyses revealed superior effects after training using Low-ModVL thresholds in all strength (Low-ModVL, ES = 0.79–2.39 vs. Mod-HighVL, ES = 0.59–1.91) and athletic (Low-ModVL, ES = 0.35–0.59 vs. Mod-HighVL, ES = 0.05–0.36) parameters. Relationship analyses showed that the adaptations produced decreased as the VL threshold increased, especially for the low loads (R2 = 0.73, p = 0.01), local endurance (R2 = 0.93, p = 0.04), and sprint ability (R2 = 0.61, p = 0.06). These findings prove that low–moderate levels of intra-set fatigue (≤25% VL) are more effective and efficient stimuli than moderate–high levels (> 25% VL) to promote strength and athletic adaptations.
Isometric knee extension test: A practical, repeatable, and suitable tool for lower-limb screening among institutionalized older adults
We aimed to analyze the isometric knee extension test (IKE) test in terms of i) intra- and inter-session repeatability, and ii) relationship with functional and body composition factors of sarcopenia among institutionalized older adults. Thirteen institutionalized older adults (age = 87 ± 10 years, body mass [BM] = 73.1 ± 10.9 kg, body mass index [BMI] = 28.5 ± 3.8 kg·m2) were recruited from a nursing home. Variability of maximal isometric force registered in three IKE trials performed on the same day was used to examine intra-session repeatability, whereas inter-session repeatability was analyzed by comparing maximal isometric force from two different days. Furthermore, functional (Handgrip, 6-m Gait Speed, Time Up and Go [TUG], and Sit-to-stand tests) and body composition (appendicular lean mass adjusted by BMI, ALM/BMI) evaluations were conducted. Statistics included the intraclass correlation coefficient (ICC) and the standard error of measurement (SEM), expressed in both absolute (N·kg-1) and relative terms (coefficient of variation, CV = 100 × SEM / mean). High to very high intra-session repeatability was found for both the dominant and non-dominant legs (CV ≤ 6.0%, ICC ≥ 0.989). Similarly, both legs showed high inter-session repeatability (SEM ≤ 0.26 N·kg-1, ICC ≥ 0.959). On the other hand, significant relationships were found between Dominant and Non-dominant IKE tests and 6-m Gait Speed (r = 0.77; r = 0.58), ALM/BMI (r = 0.62; r = 0.58), and Non-dominant Handgrip/BM (r = 0.60; r = 0.68). In addition, a significant association was found between Dominant IKE/BM and TUG (r = -0.74), as well as between Non-dominant IKE/BM and Dominant Handgrip/BM (r = 0.67). These findings suggest that the IKE test is a repeatable and suitable strategy for lower-limb screening in institutionalized older adults.
A comprehensive analysis of the velocity-based method in the shoulder press exercise: stability of the load-velocity relationship and sticking region parameters
The purpose of this study was threefold: i) to analyse the load-velocity relationship of the shoulder press (SP) exercise, ii) to investigate the stability (intra-individual variability) of this load-velocity relationship for athletes with different relative strength levels, and after a 10-week velocity-based resistance training (VBT), and iii) to describe the velocity-time pattern of the SP: first peak velocity [Vmax1], minimum velocity [Vmin], and second peak velocity [Vmax2]. This study involves a cross-sectional (T1, n = 48 subjects with low, medium and high strength levels) and longitudinal (T2, n = 24 subjects randomly selected from T1 sample) design. In T1, subjects completed a progressive loading test up to the 1RM in the SP exercise. The barbell mean, peak and mean propulsive velocities (MV, PV and MPV) were monitored. In T2, subjects repeated the loading test after 10 weeks of VBT. There were very close relationships between the %1RM and velocity attained in the three velocity outcomes (T1, R2: MV = 0.970; MPV = 0.969; PV = 0.954), being even stronger at the individual level (T1, R2 = 0.973–0.997). The MPV attained at the 1RM (~0.19 m·s-1) was consistent among different strength levels. Despite the fact that 1RM increased ~17.5% after the VBT programme, average MPV along the load-velocity relationship remained unaltered between T1 and T2 (0.69 ± 0.06 vs. 0.70 ± 0.06 m·s-1). Lastly, the three key parameters of the velocity-time curve were detected from loads > 74.9% 1RM at 14.3% (Vmax1), 46.1% (Vmin), and 88.7% (Vmax2) of the concentric phase. These results may serve as a practical guideline to effectively implement the velocity-based method in the SP exercise.
Running power meters and theoretical models based on laws of physics: effects of environments and running conditions
Training prescription and load monitoring in running activities have benefited from power output (PW) data offered by new technologies. Nevertheless, to date, the sensitivity of PW data provided by these tools is still not completely clear. The aim of this study was to analyze the level of agreement between the PW estimated by five commercial technologies and the two main internationally theoretical models based on laws of physics, in different environments and running conditions. Ten endurance-trained male athletes performed three submaximal running protocols on a treadmill (indoor) and an athletic track (outdoor), with changes in speed, body weight, and slope. PW was simultaneously registered by the commercial technologies Stryd (StrydApp and StrydWatch), RunScribe, GarminRP and PolarV, whereas theoretical power output (TPW) was calculated by the two mathematical models (TPW1 and TPW2). Statistics included, among others, the Pearson's correlation coefficient (r) and standard error of measurement (SEM). The PolarV, and above all Stryd, showed the closest agreement with the TPW1 (Stryd: r ≥ 0.947, SEM ≤ 11 W; PolarV: r ≥ 0.931, SEM ≤ 64 W) and TPW2 (Stryd: r ≥ 0.933, SEM ≤ 60 W; PolarV: r ≥ 0.932, SEM ≤ 24 W), both indoors and outdoors. On the other hand, the devices GarminRP (r ≤ 0.765, SEM ≥ 59 W) and RunScribe. (r ≤ 0.508, SEM ≥ 125 W) showed the lowest agreement with the TPW1 and TPW2 models for all conditions and environments analyzed. The closest agreement of the Stryd and PolarV technologies with the TPW1 and TPW2 models suggest these tools as the most sensitive, among those analyzed, for PW measurement when changing environments and running conditions.
Adaptations in athletic performance and muscle architecture are not meaningfully conditioned by training free-weight versus machine-based exercises: Challenging a traditional assumption using the veloicity-based method
Level of effort: a reliable and practical alternative to the velocity-based approach for monitoring resistance training
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 (nRM) 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 nRM 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. nRM 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 (R2 ≥ 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.
Effects of resistance training modality on physical performance and muscle structure
Mediante una rigurosa metodología de evaluación y programación, el objetivo principal de esta Tesis Doctoral fue comparar el efecto del entrenamiento de fuerza con peso libre o con maquinaria guiada sobre el rendimiento físico y la estructura muscular. Esta metodología fue examinada en profundidad en los Estudios I y II (Artículos 1-5) y posteriormente implementada en los Artículos desarrollados para abordar la principal pregunta de investigación subyacente a este proyecto (Estudio III, Artículos 6 y 7). El Artículo 1 analizó la relación carga-velocidad (C-V) de las modalidades con peso libre y máquina guiada de los ejercicios sentadilla (SC), press de banca (PB), remo dorsal (RD) y press de hombros (PH), así como examinar la influencia del nivel de fuerza del sujeto en estas relaciones C-V. Los análisis mostraron altos ajustes (R2 0,95) para las 8 relaciones C-V, las cuales revelaron no estar condicionadas por el nivel de fuerza pero si por la modalidad de entrenamiento (velocidades significativamente más rápidas para la variante de peso libre). El Artículo 2 examinó la idoneidad del Carácter del Esfuerzo como metodología para programar la intensidad y el volumen intraserie en los ejercicios SC, PB, RD y PH. Independientemente del nivel de fuerza del sujeto, este estudio encontró una baja variabilidad inter- (Intervalo de confianza, IC 95% 4 repeticiones) e intra-sujeto (Error estándar de la medida, EEM 2 repeticiones) en el número de repeticiones hasta el fallo, así como una alta relación (R2 0,97) entre las repeticiones completadas y la pérdida de velocidad incurrida. Los Artículos 3 y 4 cuantificaron los errores de adquisición y análisis cometidos al implementar la ecografía para evaluar el área de sección transversal anatómica (ASTA) del pectoral mayor (Artículo 3) y del cuádriceps (Artículo 4). Los errores de adquisición incluyeron la comparación de dos imágenes registradas con 5 minutos de diferencia, mientras que la primera adquisición se analizó dos veces para cuantificar los errores de análisis. Además, la ASTA de la primera adquisición se comparó con la obtenida mediante resonancia magnética (RM). Estos errores se cuantificaron para un ecografista entrenado y otro novato. Ambos artículos revelaron pequeños errores (especialmente para el ecografista entrenado) al adquirir y analizar el ASTA de estos músculos, así como un elevado acuerdo con la RM. Por otra parte, el Artículo 5 examinó el acuerdo entre el ASTA medida mediante ecografía y RM, así como la validez y fiabilidad de dos enfoques del método de 2 puntos (utilizando las regiones del muslo del 30-60% o del 20-70%) para estimar el ASTA del cuádriceps femoral obtenido mediante ecografía. Además de una concordancia casi perfecta (r 0,968) entre la ecografía y la RM, este estudio halló bajos errores de estimación y de test-retest para el método de 2 puntos20-70% (SEM 5,67 cm2), pero especialmente para el método de 2 puntos30-60% (SEM 3,62 cm2). Todos estos resultados sentaron las bases metodológicas del Estudio III. Los Artículos 6 y 7 compararon el efecto del entrenamiento de fuerza con peso libre o con máquinas guiadas sobre el rendimiento físico, la estructura muscular y los niveles de malestar. Para ello, 34 (Artículo 6) y 38 (Artículo 7) varones completaron un entrenamiento controlado por velocidad de 8 semanas de duración, asignados al grupo de peso libre o máquina guiada. Todos los parámetros de entrenamiento fueron idénticos para ambos grupos, por lo que sólo se diferenciaron en el uso de una barra o máquinas específicas para realizar los ejercicios SC, PB, RD y PH. Se compararon los cambios en el rendimiento físico mediante 5 tests atléticos (sprint, cambio de dirección, salto vertical, equilibrio, rendimiento cíclico anaeróbico de miembros superiores e inferiores) y 8 tests de fuerza. Se midió la ASTA del cuádriceps, pectoral mayor y recto abdominal, así como la arquitectura muscular del vasto lateral, para examinar los cambios estructurales. Además, se administraron los cuestionarios DASH y WOMAC para evaluar los cambios en las molestias de las extremidades superiores e inferiores, respectivamente. Los resultados de ambos estudios sugieren que las modalidades de entrenamiento con peso libre y con máquinas guiadas tendrían una eficacia similar sobre el rendimiento físico y los cambios estructurales sin aumentar las molestias articulares.