A Biomechanical Comparison of the Back Squat and Hexagonal Barbell Deadlift.

ABSTRACT: Stahl, CA, Regni, G, Tanguay, J, McElfresh, M, Trihy, E, Diggin, D, and King, DL. A biomechanical comparison of the back squat and hexagonal barbell deadlift. J Strength Cond Res 38(5): 815-824, 2024-Coaches often use different exercises to encourage similar strength adaptations and limit monotony. Anecdotally, the hexagonal barbell deadlift (HBD) exhibits similarities to the back squat (BS). To date, research has not examined the empirical differences between these exercises. This study examined kinematic and kinetic differences between the BS and the HBD across different loads. Sixteen resistance-trained individuals (6 men and 10 women) volunteered to participate. Subjects performed 1-repetition maximum (1RM) testing under BS and HBD conditions. Kinematic and kinetic data were collected during performance of both exercises at submaximal (warm-up sets) and maximal (1RM) loads using a 3D motion capture and force-plate system. Results showed that subjects lifted greater 1RM loads in the HBD relative to the BS (p < 0.05; d = -1.75). Kinematic data indicated that subjects exhibited greater maximum forward lean of the trunk and decreased maximum knee flexion while performing the HBD compared with the BS. The BS resulted in higher maximum extension moments at the hip joint than the HBD. Maximum extension moments at the knee joint showed no difference between the exercises. Data suggest that bar design and position facilitate balanced moment arm length at hip and knee joints during performance of the HBD. By contrast, bar position during performance of the BS increases moment arm length at the hip joint, making it a hip-dominant exercise. The present data have implications for the programming of both exercises. Future research should examine differences in muscle-activation strategies between the 2 exercises.

Distinct components of cardiovascular health are linked with age-related differences in cognitive abilities.

Cardiovascular ageing contributes to cognitive impairment. However, the unique and synergistic contributions of multiple cardiovascular factors to cognitive function remain unclear because they are often condensed into a single composite score or examined in isolation. We hypothesized that vascular risk factors, electrocardiographic features and blood pressure indices reveal multiple latent vascular factors, with independent contributions to cognition. In a population-based deep-phenotyping study (n = 708, age 18-88), path analysis revealed three latent vascular factors dissociating the autonomic nervous system response from two components of blood pressure. These three factors made unique and additive contributions to the variability in crystallized and fluid intelligence. The discrepancy in fluid relative to crystallized intelligence, indicative of cognitive decline, was associated with a latent vascular factor predominantly expressing pulse pressure. This suggests that higher pulse pressure is associated with cognitive decline from expected performance. The effect was stronger in older adults. Controlling pulse pressure may help to preserve cognition, particularly in older adults. Our findings highlight the need to better understand the multifactorial nature of vascular aging.

Effect of Varying Self-myofascial Release Duration on Subsequent Athletic Performance.

ABSTRACT: Phillips, J, Diggin, D, King, DL, and Sforzo, GA. Effect of varying self-myofascial release duration on subsequent athletic performance. J Strength Cond Res 35(3): 746-753, 2021-Self-myofascial release (SMR) treatments can enhance joint range-of-motion and restore movement function. The effects of different SMR durations on athletic performance have yet to be examined. Twenty-four volunteers had ankle and knee joint range-of-motion assessed using modified weight-bearing and kneeling lunge (KL) tests. Vertical jump and pro-agility sprint performance were also examined. All tests were conducted before and immediately after 1 (SMR_1) and 5 minutes (SMR_5) of foam rolling, and immediately after a control (CONTR) condition. Results showed KL scores increased after SMR_5 (16.4%; effect size [ES] = 0.85) when compared with SMR_1 (12.5%; ES = 0.58). Weight-bearing lunge scores showed little change after either SMR treatment. The CONTR condition exhibited little effect on joint range-of-motion. Vertical jump performance decreased after SMR_5 (5.1%; ES = 0.26) but changed little after SMR_1 (0.7%; ES = 0.03) and CONTR (1.9%; ES = 0.10) conditions. Pro-agility performance improved slightly after SMR_1 (1.1%) but deteriorated after CONTR (1.2%) and SMR_5 (0.5%). Effect size calculations for changes in pro-agility sprint times were trivial across all conditions (0.06-0.15). Data suggest that extended periods of SMR may be recommended, should improvements in joint range-of-motion be required. If power output is a critical requirement of subsequent exercise/performance tasks, prolonged SMR treatment (i.e., 5 minutes) should be avoided. Practitioners should be cautious when implementing SMR treatments within warm-ups.

Initial contact and toe off event identification for rearfoot and non-rearfoot strike pattern treadmill running at different speeds.

The purpose of this study was to determine the validity of kinematic based initial contact (IC) and toe-off (TO) identification algorithms for rearfoot and non-rearfoot runners across a broad range of treadmill running speeds. 14 healthy active participants completed six 20-60 s treadmill running trials at 6 speeds: 2.24, 2.68, 3.13, 3.58, 4.02, and 4.48 ms-1. 3D kinematic data were collected for the last 20 s of each trial. Force plates (FP) were used as the gold standard to determine ICFP and TOFP for each step. Three algorithms for finding IC, ICMilner, ICAlvim, ICAlvim-mod, and one algorithm for finding toe off, TOFellin, were chosen for analysis. Root mean square errors (RMSE) and difference scores with 95% confidence intervals were computed for IC, TO and stance time (ST). ICAlvim RMSE ranged from 0.175 to 0.219 s. STAlvim RMSE ranged from 0.168 to 0.216 s. ICAlvim-mod RMSE ranged from 0.105 to 0.131 s. STAlvim-mod RMSE ranged from 0.108 to 0.129 s. ICMilner RMSE ranged 0.012 to 0.015 s. STMilner RMSE ranged 0.019 to 0.024 s. ICMilner accuracy was inversely related to speed. ICMilner corrected with a linear regression equation reduced differences to- 0.006 ±â€¯0.012 s with 86% of foot strikes identified within 20 ms and 58% with 10 ms. TOFellin RMSE ranged from 0.012 to 0.016 s. ICMilner adjusted for speed and TOFellin can be used to predict IC and TO within a broad range of treadmill running speeds (2.24-4.48 ms-1) and for rearfoot and non-rearfoot strikers.

Sustainability and repeatability of postactivation potentiation.

BACKGROUND: This study investigated the duration and repeatability of postactivation potentiation (PAP) benefits within a single exercise session. Specifically examined were the recurring effects, over multiple sets, of heavy back squats on repeated sprint times. METHODS: A partially randomized, counterbalanced, repeated measures design was implemented using 29 college-aged male NCAA varsity field sport athletes participating in PAP and control conditions. Subjects performed four repetitions of back squats (PAP=90% 1RM; control =20% 1RM), rested 8 minutes, performed a set of four 40-m sprints (55 s inter-repetition active recovery) and rested for 8 minutes after the last sprint. This was performed two more times, for a total of three sets (of back squats and sprints) performed 20 minutes apart. Sprint performance was measured using electronic timing gates and a timing pad to capture of reaction time (RT) at the start of each sprint. 2x3 (condition x sets) and 2x4 (condition X repetition) repeated measures ANOVAs were used to analyze both sprint and RT outcomes. RESULTS: Subjects ran significantly faster (P<0.05) after PAP than control. Specifically, sprint times were faster for the first two-three sprints, but not the fourth, across all three sets of sprints over the 51-min exercise session. RT was not affected (P>0.05) by PAP activity. CONCLUSIONS: The PAP effect was sustainable up to 11 minutes after heavy back squats and was repeated successfully three times. These findings can assist coaches and athletes interested in applying PAP to improve performance.

Validity and Intrarater Reliability of 2-Dimensional Motion Analysis Using a Handheld Tablet Compared to Traditional 3-Dimensional Motion Analysis.

CONTENT: Lower extremity landing mechanics have been implicated as a contributing factor in knee pain and injury, yet cost effective and clinically accessible methods for evaluating movement mechanics are limited. The identification of valid, reliable, and readily accessible technology to assess lower extremity alignment could be an important tool for clinicians, coaches, and strength and conditioning specialists. OBJECTIVE: The purpose of this study was to examine the validity and reliability of using a hand-held tablet and movement analysis application (app) for assessing lower extremity alignment during a drop vertical jump task. DESIGN: Concurrent Validation. SETTING: Laboratory. PARTICIPANTS: Twenty-two healthy college aged subjects (11 female and 11 male, mean age = 21 ± 1.4 years; mean height: 1.73 ± .12 m, mean mass: 71 ± 13 kg) with no lower extremity pathology that prevented safe landing from a drop jump. INTERVENTION: Subjects performed six drop vertical jumps which were recorded simultaneously using a 3D motion capture system and a hand-held tablet. MAIN OUTCOME MEASURES: Angles on the tablet were calculated using a motion analysis app and from the 3D motion capture system using Visual 3D. Hip and knee angles were measured and compared between both systems. RESULTS: Significant correlations between the tablet and 3D measures for select frontal and sagittal plane ranges of motion (ROM) and angles at maximum knee flexion (MKF) ranged from r = 0.48 (P = .036) for frontal plane knee angle at MKF to r = .77 (P<.001) for knee flexion at MKF. CONCLUSION: Results of this study suggest that a hand-held tablet and app may be a reliable method for assessing select lower extremity joint alignments during drop vertical jumps, but this technology should not be used to measure absolute joint angles. However, sports medicine specialists could use a hand-held tablet to reliably record and evaluate lower extremity movement patterns on the field or in the clinic.

Reliability of Using a Handheld Tablet and Application to Measure Lower-Extremity Alignment Angles.

CONTEXT: Landing kinematics have been identified as a risk factor for knee injury. Detecting atypical kinematics in clinical settings is important for identifying individuals at risk for these injuries. OBJECTIVE: To determine the reliability of a handheld tablet and application (app) for measuring lower-extremity kinematics during drop vertical-jump landings. DESIGN: Measurement reliability. SETTING: Laboratory. PARTICIPANTS: 23 healthy young adults with no lower-extremity injuries and no contraindications for jumping and landing. INTERVENTION: Subjects performed 6 drop vertical jumps that were captured with an iPad2 and analyzed with a KinesioCapture app by 2 novice and 2 experienced raters. Three trials each were captured in the frontal and sagittal planes. MAIN OUTCOME MEASURES: Frontal-plane projection angles, knee flexion, and hip flexion at initial contact and maximum knee flexion were measured. ICC and SEM were calculated to determine intertrial and interrater reliability. One-way ANOVAs were used to examine differences between the measured angles of the raters. RESULTS: Average intertrial reliability ranged from .71 to .98 for novice raters and .77 to .99 for experienced raters. SEMs were 2.3-4.3° for novice raters and 1.6-3.9° for experienced raters. Interrater ICC2,1 was.39-.98 for the novice raters and .69-.93 for the experienced raters. SEMs were smallest with the experiences raters, all less than 1.5°. CONCLUSION: A handheld tablet and app is promising for evaluating landing kinematics and identifying individuals at risk for knee injury in a clinical setting. Intertrial reliability is good to excellent when using average trial measures. Interrater reliability is fair to excellent depending on experience level. Multiple trials should be assessed by a single rater when assessing lower-extremity mechanics with a handheld tablet and app, and results may vary with experience level or training.

A novel running mechanic's class changes kinematics but not running economy.

A novel method of running technique instruction, Midstance to Midstance Running (MMR), was studied to determine how MMR affected kinematics and running economy (RE) of recreational runners. An experimental pre-post randomized groups design was used. Participants (n = 18) were recreational runners who ran at least 3 days a week and 5 km per run. All testing was performed on a treadmill at 2.8 m·s. The intervention group (n = 9) completed 8 weeks of instruction in MMR; the control group (n = 9) continued running without instruction. The MMR group showed significant decreases in stride length (SL) (p = 0.02) and maximum knee flexion velocity in stance (p = 0.01), and a significant increase in stride rate (SR) (p = 0.02) after 8 weeks. No significant changes were found in heart rate, rating of perceived exertion, or RE. Midstance to Midstance Running was effective in changing SR and SL, but was not effective in changing other kinematic variables such as foot contact position and maximum knee flexion during swing. Midstance to Midstance Running did not affect RE. Evidence suggests that MMR may be an appropriate instructional method for recreational runners trying to decrease SL and increase SR.

Optimizing power output by varying repetition tempo.

The effects of varying interrepetition rest and eccentric velocity on power output (PO) and the number of repetitions performed during a bench press set were examined in 24 college-aged resistance trained men. On 6 separate occasions, subjects performed a set of bench press at 80% 1 repetition maximum until volitional fatigue. For each of the 6 repetition tempo trials, the bench press set was paced by metronome to a unique repetition tempo involving a combination of the following: interrepetition rest of 0 or 4 seconds; eccentric velocity of 1 or 4 seconds and bottom rest of 0 or 3 seconds. The velocity of concentric contraction was maximal during all 6 tempo trials. During each trial, video data were captured to determine PO variables and number of successful repetitions completed at each tempo. One-way repeated measures analysis of variance showed tempos with a fast eccentric phase (1 second), and no bottom rest produced significantly greater (p ≤ 0.05) PO and repetitions than tempos involving slower eccentric velocity (4 seconds) or greater bottom rest (4 seconds). This combination of greater repetitions and PO resulted in a greater volume of work. Varying interrepetition rest (1 or 4 seconds) did not significantly affect PO or repetitions. The results of this study support the use of fast eccentric speed and no bottom rest during acute performance testing to maximize PO and number of repetitions during a set of bench press.

Comparison of split double and triple twists in pair figure skating.

In this study, we compared the kinematic variables of the split triple twist with those of the split double twist to help coaches and scientists understand these landmark pair skating skills. High-speed video was taken during the pair short and free programmes at the 2002 Salt Lake City Winter Olympics and the 2003 International Skating Union Grand Prix Finals. Three-dimensional analyses of 14 split double twists and 15 split triple twists from eleven pairs were completed. In spite of considerable variability in the performance variables among the pairs, the main difference between the split double twists and split triple twists was an increase in rotational rate. While eight of the eleven pairs relied primarily on an increased rotational rate to complete the split triple twist, three pairs employed a combined strategy of increased rotational rate and increased flight time due predominantly to delayed or lower catches. These results were similar to observations of jumps in singles skating for which the extra rotation is typically due to an increase in rotational velocity; increases in flight time come primarily from delayed landings as opposed to additional height during flight. Combining an increase in flight time and rotational rate may be a good strategy for completing the split triple twist in pair skating.

Performing triple and quadruple figure skating jumps: implications for training.

The purpose of this paper is to review the biomechanics of triple and quadruple figure skating jumps, focusing on information that has implications for strength and conditioning programs. At a minimum, to complete the required revolutions in a jump, a skater must balance the average angular velocity with the time in the air. Vertical velocity at takeoff is similar in high revolution jumps to that in low revolution jumps; however, when comparing skaters of different abilities, those with higher abilities generate greater vertical velocities at takeoff for the same type of jump. Powerful extension of the legs is the primary factor in generating vertical velocity. Some jumps use asymmetrical extension of both legs, while other jumps involve extension of only one leg. Angular velocity is controlled primarily by the skater's moment of inertia, which means skaters must forcefully arrest the motion of the arms and legs after the propulsion phase and then quickly position the arms and legs close to the axis of rotation during flight. Training exercises that emphasize eccentric and concentric muscle actions and which are adaptable to asymmetrical or unilateral motions, such as box jumps and medicine ball throws, are a crucial component to off-ice training programs for figure skaters.

Periods of extreme ankle displacement during one-legged standing.

The goal of this study was to describe the movement patterns of the ankle joint whilst standing on one leg. Ten healthy adult females (age 24 +/- 5.3 years) performed a one-legged standing task with eyes closed. Force platform recordings and video analyses were used to describe the kinematic and kinetic characteristics of the ankle joint during this task. A rocking movement of the foot (heel inversion-eversion) was documented by examining instances of extreme ankle displacement. Extreme ankle displacement was defined as any instant when the ankle position was more than +/- 2 SD away from the mean ankle joint position. Extreme values of lateral and medial ankle joint displacement were 14.8 and 9.2 mm, correspondingly. These instances of extreme foot inversion-eversion were characterized by large medial-lateral displacement of the gravity line (GLP) and center of pressure (COP) and large horizontal forces. Comparing instances of extreme ankle joint displacement to periods of non-extreme ankle displacement, the ankle joint moment remained fairly constant, averaging 8.4 +/- 4 and 6.9 +/- 3.5 Nm, respectively. The moment about the 'body-minus-foot' center of mass generated by the ankle joint reaction force, however, was on average over four times larger during instances of extreme ankle displacement (3.4 +/- 2.8 Nm), than during periods of non-extreme ankle displacement (0.8 +/- 0.4 Nm). In utmost situations, the moment due to the joint reaction force was up to 73% of the ankle joint moment. These results suggest that at least two different techniques are used to maintain balance during one-legged standing. The first technique, termed the ankle torque technique, involves a large restorative moment at a stationary ankle joint for balance maintenance. The other technique, the shear force technique, involves a large horizontal force at a moving ankle joint for balance maintenance. During non-extreme periods, balance was maintained primarily through the ankle torque technique. During extreme instances, a combination of both techniques was observed.