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The purpose of this study was to investigate whether the ballistic push-up (BPU) is responsive to post-activation performance enhancement (PAPE) after a bench press conditioning exercise using velocity-based repetition control. Additionally, we aimed to evaluate the effects of range of motion (ROM) conditions on subsequent BPU performance. In a randomized crossover design, 18 males performed two conditions (full ROM and self-selected partial ROM) of bench press at 80% of their 1RM until mean concentric velocity dropped 10%. Each participant performed two pre- and six post-test BPUs to assess the PAPE effect. Paired sample t-tests assessed bench press performance measures. Multiple two-way repeated measures ANOVAs assessed differences in flight time, impulse, and peak power for the pre- and post-test BPUs. No significant differences existed between ROM conditions for total repetitions, volume load, or peak velocity. Compared to partial ROM, full ROM showed greater displacement (0.42 ± 0.05 vs. 0.34 ± 0.05 m), work (331.99 ± 67.72 vs. 270.92 ± 61.42 J), and mean velocity (0.46 ± 0.09 vs. 0.44 ± 0.08 m/s). Neither bench press ROM condition enhanced the BPU and were detrimental in some cases. Several time points showed partial ROM (flight time: 2 min post, impulse: 12 min post, peak power: 12 min post) significantly greater than full ROM, possibly indicating less fatigue accumulation. The BPU may require a different stimulus or may not be practical for PAPE effects in college-aged males. Partial ROM can be an alternative that achieves similar peak velocities while requiring less overall work.

Abstract: Klawitter, LA, Hackney, KJ, Christensen, BK, Hamm, JM, Hanson, M, and McGrath, R. Using electronic handgrip dynamometry and accelerometry to examine multiple aspects of handgrip function in master endurance athletes: A Pilot Study. J Strength Cond Res 37(9): 1777-1782, 2023-Electronic handgrip dynamometry and accelerometry may provide novel opportunities to comprehensively measure muscle function for human performance, especially for master athletes. This investigation sought to determine the multivariate relationships between maximal strength, asymmetry, rate of force development, fatigability, submaximal force control, bimanual coordination, and neuromuscular steadiness to derive one or more handgrip principal components in master-aged endurance athletes. We included n = 31 cyclists and triathletes aged 35-70 years. Maximal strength, asymmetry, rate of force development, fatigability, submaximal force control, bimanual coordination, and neuromuscular steadiness were measured twice on each hand using electronic handgrip dynamometry and accelerometry. The highest performing measures were included in the analyses. A principal component analysis was conducted to derive a new collection of uncorrelated variables from the collected handgrip measurements. Principal components with eigenvalues >1.0 were kept, and individual measures with a factor loading of |>0.40| were retained in each principal component. There were 3 principal components retained with eigenvalues of 2.46, 1.31, and 1.17. The first principal component, "robust strength," contained maximal strength, rate of force development, submaximal force control, and neuromuscular steadiness. The second principal component, "bilateral synergy," contained asymmetry and bimanual coordination, whereas the third principal component, "muscle conditioning," contained fatigability. Principal components 1, 2, and 3 explained 44.0, 31.6, and 24.4% of the variance, respectively. Different dimensions of muscle function emerged from our findings, suggesting the potential of a muscle function battery. Further research examining how these measures are associated with appropriate human performance metrics and lower extremity correlates is warranted., Competing Interests: This research was funded by an intramural pilot mechanism at North Dakota State University. The results of this study do not constitute endorsement of the product by the authors or the NSCA. The authors report no conflicts of interest., (Copyright © 2023 National Strength and Conditioning Association.)

Analyzing the severity of handgrip strength (HGS) asymmetry in aging populations may help to screen for morbidities and add utility to handgrip dynamometer testing. Our study sought to determine the relationships between HGS asymmetry severity and future accumulating morbidities in older Americans. Secondary analyses from the 2006-2016 waves of the Health and Retirement Study included 18,506 adults ≥ 50 years old. The highest recorded HGS values from each hand were used to calculate HGS asymmetry ratio (non-dominant HGS/dominant HGS). If the HGS asymmetry ratio < 1.0, it was inversed to make all asymmetry ratios ≥ 1.0. Participants were categorized into groups based on the severity of their HGS asymmetry ratio: 1) 0.0% - 10.0%, 2) 10.1% - 20.0%, 3) 20.1% - 30.0%, and 4) > 30.0%. Healthcare provider-diagnosed morbidities (hypertension, diabetes, cancer, chronic lung disease, cardiovascular disease, stroke, arthritis, and psychiatric problems) were self-reported. Covariate-adjusted ordinal generalized estimating equations evaluated the relationships between HGS asymmetry severity on future accumulating morbidities. Results showed 8,936 (48.3%) participants had HGS asymmetry 0.0%-10.0%, 6,105 (33.0%) participants had HGS asymmetry 10.1%-20.0%, 2,411 (13.0%) participants had HGS asymmetry 20.1%-30.0%, and 1,054 (5.7%) participants had HGS asymmetry > 30.0%. Overall, every 10% increase in HGS asymmetry was associated with a 1.17 (CI: 1.05, 1.32) greater odds of future morbidity accumulation. Additionally, asymmetry between 10.1% - 20.0%, 20.1% - 30.0%, and > 30.0% was associated with a 1.10 (CI: 1.05, 1.15), 1.11 (CI: 1.04, 1.18), and 1.20 (CI: 1.09, 1.33) greater odds for morbidity accumulation during aging. These findings suggest that severe functional asymmetries may elevate the odds for accumulating morbidities.

Abstract: Collins, KS, Klawitter, LA, Waldera, RW, Mahoney, SJ, and Christensen, BK. Differences in muscle activity and kinetics between the goblet squat and landmine squat in men and women. J Strength Cond Res 35(10): 2661-2668, 2021-Squat exercise variations are widely used and extensively researched. However, little information exists on the goblet squat (GBS) and landmine squat (LMS) and differences between men and women. This study investigated the differences in muscle activity and kinetics between the GBS and the LMS in 16 men and 16 women. Five repetitions of each squat type were performed loaded at 30% of their body mass. Vertical and anteroposterior ground reaction forces for the eccentric and concentric phases and peak vertical force were recorded with a force plate. Electromyographic (EMG) signals were recorded for the vastus medialis (VM), vastus lateralis (VL), semitendinosus (ST), and biceps femoris (BF). Normalized mean EMG values and ground reaction forces were analyzed with repeated measures analysis of variance (p < 0.05). Significant main effects for squat condition and sex were found. The LMS reduced activity in the quadriceps (VM and VL) muscles and vertical forces, while increasing posterior horizontal forces. In the LMS, men showed decreased ST activity, whereas women had decreased BF activity. Women exhibited greater quadriceps activity in both the GBS and LMS and greater ST in the LMS. Women also produced greater eccentric vertical force in both the GBS and LMS and less posterior horizontal forces in the LMS. The LMS may be useful to balance hamstring to quadriceps activity, increase horizontal loading, and reduce vertical loading. Conversely, the GBS can better target quadriceps activity and increase vertical loading. Sex differences should be considered for training programs that include the GBS and LMS., (Copyright © 2021 National Strength and Conditioning Association.)

The effect of pre-inoculation temperature on the subsequent growth of Listeria monocytogenes Scott A at 5 degrees C was examined in microbiological medium, UHT milk, canned dog food, and raw ground beef (untreated and irradiation-sterilized). In microbiological medium, the duration of the lag phase was decreased when aerobic and anaerobic cultures were initially grown at less than or equal to 28 and less than or equal to 13 degrees C, respectively. Subsequent exponential growth rates and maximum population densities of the 5 degrees C cultures were not affected by temperature history. Differences in lag phase durations were also observed when L. monocytogenes initially cultured at 19 and 37 degrees C were grown at 5 degrees C in UHT milk and some of the canned dog food varieties. Growth of L. monocytogenes was not observed in either untreated or irradiation-sterilized raw ground beef. While temperature history can affect the growth kinetics of L. monocytogenes at 5 degrees C, it did not account for the lack of growth in raw meat, suggesting that there is an inhibitory condition or component in ground beef that is lost upon cooking.