Effect of High-Intensity Interval Treadmill Exercise on Subsequent Lower and Upper Limb Strength Performance

Purpose: The aim of this study was to analyze the acute effect of a treadmill high-intensity interval protocol on subsequent upper body and lower body strength exercise performance. Method: Sixteen young men had their maximal aerobic capacity and one-repetition maximum (1RM) determined and underwent four randomized conditions: a half-squat control session; a bench press control session; a treadmill interval protocol followed by a half-squat experimental session; and a treadmill interval protocol followed by a bench press experimental session. During the control sessions, four sets to failure for each exercise were performed at 80% of 1RM. In the experimental sessions, participants performed eight sprints of 40 s at 100% velocity of maximal oxygen uptake with 20 s of passive interval between them, followed by the same strength exercise protocol of the control sessions. The number of repetitions during each protocol and participants' heart rate (HR),and blood lactate concentration ([lac]) were compared pre and post protocols and exercises. Results: Fewer repetitions were completed in the experimental session compared to the control sessions (p < .001). Moreover, the reduction in number of repetitions performed was more evident in half-squat compared to bench press (p = .018). HR was higher at the end of sessions with the interval protocol for both exercises (p < .001). The [lac] was higher at the end of session with the interval protocol for half-squat (p = .003). Conclusions: These findings suggest that previous high-intensity interval running may impair subsequent strength exercise performance, but the magnitude of the negative effect is greater in the lower limbs.

Cardiorespiratory Parameters Comparison Between Incremental Protocols Performed in Aquatic and Land Environments by Healthy Individuals: A Systematic Review and Meta-Analysis

BACKGROUND

Physical properties of water cause physiological changes in the immersed human body compared with the land environment. Understanding the magnitude of cardiorespiratory alterations might ensure adequate intensity control during aquatic exercise programs.

OBJECTIVE

We aimed to compare the oxygen uptake (VO₂), heart rate (HR), and rating of perceived exertion (RPE) parameters during aquatic and land incremental tests.

METHODS

Four databases (PubMed, LILACS, EMBASE, and SPORTDiscus) were searched in September 2020. Eligibility criteria included studies in a crossover design comparing aquatic and land incremental tests for healthy individuals with at least one of the following parameters: VO₂ (maximal, VO_2max; anaerobic threshold, VO_2AT), HR (HR_max; HR_AT), and RPE (RPE_max; RPE_AT). The random-effects meta-analysis included mean difference and 95% confidence interval for VO₂ and HR or standardized mean difference for RPE. The Joanna Briggs Institute Critical Appraisal tool was adapted to assess methodological quality.

RESULTS

Twenty-eight studies were eligible and included in the meta-analysis. Aquatic protocols showed lower values compared with land for VO_2max (- 7.07 mL.kg^-1.min^-1; - 8.43 to - 5.70; n = 502), VO_2AT (- 6.19 mL.kg^-1.min^-1; - 7.66 to - 4.73; n = 145), HR_max (- 11.71 bpm; - 13.84 to - 9.58; n = 503), and HR_AT (- 15.29 bpm; - 19.05 to - 11.53; n = 145). RPE_max (0.01; - 0.16 to 0.18; n = 299) and RPE_AT (- 0.67; - 1.35 to 0.02; n = 55) values were similar between aquatic and land protocols.

CONCLUSIONS

Our study reinforces the specificity of the environment during incremental tests for prescribing exercises based on physiological parameters as VO₂ and HR parameters presented lower values in aquatic protocols than land protocols. Conversely, RPE seems an interchangeable measure of exercise intensity, with similar values during the protocols in both environments. Substantial levels of heterogeneity were present for the VO_2max and HR_max meta-analyses, and as such, results should be interpreted with attention. PROTOCOL REGISTRATION: This study was registered in the International Prospective Register of Systematic Reviews (PROSPERO; CRD42020212508).

High-intensity interval running impairs subsequent upper limb strength performance

BACKGROUND

This study compared the effect of treadmill running on subsequent upper limb exercise performance in young men.

METHODS

Seventeen young men (24.8±5.2 years) completed a: 1) bench press resistance exercise control session; 2) treadmill interval running protocol followed by the bench press session; and 3) treadmill continuous running protocol followed by the bench press session. Four sets of the bench press exercise were performed at 80% of 1RM up to volitional failure. In the interval protocol, eight sprints of 40s at 100% of the velocity of maximal oxygen uptake, with 20s of passive interval between them were performed, whereas in the continuous protocol 30-min of treadmill running at 90% of the heart rate corresponding to second ventilatory threshold was performed. The number of maximal repetitions completed in each set and condition was recorded and compared using a two-way repeated measures ANOVA.

RESULTS

The interval protocol (18.7±4.9 repetitions) resulted in a reduction in the number of bench press repetitions compared to the control protocol (21.4±5.4 repetitions) (P=0.002); whereas continuous running did not affect the bench press performance (20.6±4.4 repetitions). The total number of repetitions reduced from set to set in all protocols (P<0.001).

CONCLUSIONS

The results evidenced an impairment in the upper limb strength performance after high intensity interval, but not moderate intensity continuous running, which has implication for concurrent training planning and prescription.

Characterization of the Physical Fitness of Police Officers: A Systematic Review

Marins, EF, David, GB, and Del Vecchio, FB. Characterization of the physical fitness of police officers: a systematic review. J Strength Cond Res 33(10): 2860-2874, 2019-Physical fitness tests (e.g., aerobic power, muscular endurance, and flexibility tests) are commonly used to assess the ability of police officers to perform work-related tasks. The purpose of this study was to describe, from a systematic literature review, data related to police physical fitness. The research was conducted in 5 electronic databases to search for original studies that measured physical fitness (aerobic and anaerobic capacity, strength, endurance, power, flexibility, agility, and speed) of police officers, as well as the article references. Original studies assessing objective measures of physical fitness in police officers were included, with no date restriction. Fifty-nine articles were included in the review. The studies mostly measured cardiorespiratory fitness indirectly, strength, and muscular endurance, as well as other performance components (body composition, power, flexibility, speed, agility, and anaerobic profile), with police officers generally presenting values similar or above the average of the general population. It can be concluded that intervention studies are needed to promote and incorporate programs related to improvement or maintenance of physical fitness in police officers, which would result in health benefits and specifically improvement in performance of specific tasks of police work. This review provides summary information to assist in the selection of physical fitness tests for police populations. Still, these findings have practical applications for public security agencies and its personnel responsible for the development and implementation of physical programs in policemen population.

Islets of Langerhans generate wavelike electric activity modulated by glucose concentration

The electric activity of whole islets of Langerhans was monitored for the first time in this study. Measurements were made from single islets isolated from mice, hamsters, gerbils, and rats by means of external electrodes. Well-structured synchronized potential spikes up to 0.5 mV in amplitude with a stable frequency of 0.5-2 Hz were measured. Spike generation had a glucose concentration threshold. In the physiological range of each animal species, firing rate was an approximate linear function of glucose concentration. At low glucose concentrations, firing became intermittent, i.e., in bursts, while in the physiological range and above, firing was typically continuous. Simultaneous measurements from two locations on an islet indicate that the measured activity reflects the propagation of an excitation wave throughout the islet. This, together with signal synchronization, suggests that the islets contain a functional pacemaker (FPM) from which excitation propagates by means of gap junctions to the rest of the islet cells (mostly beta-cells). Thus, the electric characteristics of the individual beta-cells are functionally masked so that the islet acts as a single functional unit. In view of the dependency of insulin secretion on the islet's electric activity, the islet glucose-insulin dose-response characteristics must be determined by those of the FPM.

The Denver universal microspectroradiometer (DUM). II. Computer configuration and modular programming for radiometry

This paper describes and discusses for microscopists and spectroscopists the choice of computer equipment and the design of programs used in the Denver Universal Microspectroradiometer (DUM). This instrument is an accurate computerized photon-counting microspectrophotometer, microspectrofluorimeter and microrefractometer. The computer is used to control the operation of the system, to acquire radiometric data of various kinds, and to reduce, analyse and output the data in a readily usable form. Since the radiometer was designed to carry out many kinds of measurements in a variety of micro- and macroscopic specimens, and since different methods of microscopy or spectroscopy have to be combined in various ways fro the study of any one specimen, no single master-program could fulfill efficiently all foreseeable requirements. Therefore, the programming developed is interactive, modular, hierarchical and hybrid. Modular interactive programming makes it possible for almost any kind of main program, applicable to almost any kind of measurement, to be assembled quickly from a collection of hierarchical subroutines. Main programs are short and composed mainly of Fortran statements calling subroutines; subroutines, in turn, automatically call other subroutines over many levels. The subroutines are independently written and optimized for maximum operational efficiency in the computer system used, or for maximum ease of transfer to other systems. This approach to programming enables someone unfamiliar with computer languages to operate the radiometric system from the console of the CRT terminal. The writing of new main programs, by linking groups of existing subroutines, requires only a minimum acquaintance with Fortran; only the writing and revision of subroutines requires programming experience. Differences and similarities in the method of computer operation between the present system and other computerized radiometers are briefly discussed.

Improved isolation, separation and cytochemistry of living cells

1. This paper describes improved methods of obtaining, purifying and studying bulk suspensions of isolated living hepatocytes and other cells of adult rats and urodeles. 2. The cells were isolated largely by dissolving the hepatic ground substance through the extracorporeal portal perfusion and further incubation of the excised liver with 0.05% collagenase and 0.1% hyaluronidase. The different kinds of cells were then separated from one another by counter-current centrifugation. The isolated cells were examined by differential interference, phase-contrast, amplitude-contrast, ultraviolet, fluorescence and electron microscopy. Various cytochemical tests were carried out. Whenever possible, for each method of examination, the isolated cells were compared with cells of the same kind which had not undergone isolation. 3. Dye-exclusion, lysochromy, fluorescence and differential interference microscopical analysis indicated viability rates between 75 and 99%. Succinate dehydrogenase activity was preserved at a high level in nearly all isolated cells. In hepatocytes, the essentially extracellular cells. In hepatocytes, the essentially extracellular 'soluble' alkaline phosphatase activity of bile canaliculi was retained. Living hepatocytes were studied by super-modulating methods of microscopy for the first time, with somewhat unexpected findings. It now seems probable that previous methods of tissue preparation produced gross alterations in hepatocyte mitochondria. The assessment of the viability of isolated cells was re-examined. 4. The methods described may permit a more meaningful correlation between biochemical, cytochemical, ultrastructural and biophysical findings than that obtainable by the use of current methods.

Quantitative Cytochemical Observations on the Control of Respiration in Polymorphonuclear Neutrophil Leucocytes of Amphiuma Tridactylum

Quantitative effects of altering oxidative phosphorylation and respiration on the activity of the enzyme menadione reductase (NAD[P]H2:2-methyl-1,4-naphthoquinone oxidoreductase, E.C. 1 6.5.2), in stabilized polymorphonuclear neutrophil leucocytes of Amphiuma tridactylum, were studied by amplitude-contrast microscopy and microspectrophotometry.

In a general way, the rate of enzymic activity was proportional to ADP concentration and inversely proportional to the concentration of ATP. Terminal respiratory blocking by azide produced selective subtotal inhibition. Uncoupling of phosphorylation by dinitrophenol produced complex results.

Neutrophils of A. tridactylum, irrespective of their stage of maturation in the circulating blood, could be subdivided into 3 metabolic classes: Class I cells, of low enzymic activity (predominantly mitochondrial), greatly activated by ADP, somewhat activated by ATP, and only slightly inhibited by dinitrophenol; Class II cells, twice as active as Class I (in which the endoplasmic reticulum and idiozome were as active as the mitochondria), further activated by ADP used alone or with dinitrophenol, and unaffected by ATP or dinitrophenol; Class III, hyperactive cells (enzymic localization identical with that in Class II), inhibited by ATP and dinitrophenol, and not activated by ADP. Some of the mitochondria of Class III neutrophils retained nearly a third of their reductase activity when the reaction mixture contained 10-1 azide.

There is reason to believe that Class I neutrophils may form a reserve population of vegetative cells; in vitro, they can be transformed into Class II cells when a high concentration of ADP is added. Class II and Class III cells are potentially capable of amoeboid movement and phagocytosis. The metabolic mobilization of neutrophils could be interpreted as being controlled by 2 different feedback mechanisms: activation by ADP in cells of Classes I and II, and inhibition by ATP in cells of Class III.