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Richard Latzel, Olaf Hoos, Sebastian Stier, Sebastian Kaufmann, Volker Fresz, Dominik Reim and Ralph Beneke

, respectively, were defined as the corresponding amounts of energy divided by the duration of the BEST. Assuming a fractional replenishment of high-energy phosphates during short breaks in between circuits ( W PCr-adj ), 14 an alternative adjusted model was constructed (Figure  1 ). As breaks were too short (8

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Greg Cox, Iñigo Mujika, Douglas Tumilty and Louise Burke

This study investigated the effects of acute creatine (Cr) supplementation on the performance of elite female soccer players undertaking an exercise protocol simulating match play. On two occasions, 7 days apart, 12 players performed 5 X 11-min exercise testing blocks interspersed with 1 min of rest. Each block consisted of 11 all-out 20-m running sprints, 2 agility runs, and 1 precision ball-kicking drill, separated by recovery 20-m walks, jogs, and runs. After the initial testing session, subjects were assigned to either a CREATINE (5 g of Cr, 4 times per day for 6 days) or a PLACEBO group (same dosage of a glucose polymer) using a double-blind research design. Body mass (BM) increased (61.7 ± 8.9 to 62.5 ± 8.9 kg, p < .01) in the CREATINE group; however, no change was observed in the PLACEBO group (63.4 ± 2.9 kg to 63.7 ± 2.5 kg). No overall change in 20-m sprint times and agility run times were observed, although the CREATINE group achieved faster post-supplementation times in sprints 11, 13, 14, 16, 21, 23, 25, 32, and 39 (p < .05), and agility runs3,5,and8 (p < .05). The accuracy of shooting was unaffected in both groups. In conclusion, acute Cr supplementation improved performance of some repeated sprint and agility tasks simulating soccer match play, despite an increase in BM.

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Philip Davis, Renate M. Leithäuser and Ralph Beneke

The energy expenditure of amateur boxing is unknown.

Purpose:

Total metabolic cost (Wtot) as an aggregate of aerobic (Waer), anaerobic lactic (W[lactate]), and anaerobic alactic (WPCr) energy of a 3 × 2-min semicontact amateur boxing bout was analyzed.

Methods:

Ten boxers (mean ± SD [lower/upper 95% confidence intervals]) age 23.7 ± 4.1 (20.8/26.6) y, height 180.2 ± 7.0 (175.2/185.2) cm, body mass 70.6 ± 5.7 (66.5/74.7) kg performed a semicontact bout against handheld pads created from previously analyzed video footage of competitive bouts. Net metabolic energy was calculated using respiratory gases and blood [lactate].

Results:

Waer, 526.0 ± 57.1 (485.1/566.9) kJ, was higher (P < .001) than WPCr, 58.1 ± 13.6 (48.4/67.8) kJ. W[lactate], 26.2 ± 7.1 (21.1/31.3) kJ, was lower (P < .001) than Waer and WPCr. An ~70-kJ fraction of the aerobic energy expenditure reflects rephosphorylation of high-energy phosphates during the breaks between rounds, which elevated Wtot to ~680 kJ with relative contributions of 77% Waer, 19% WPCr, and 4% W[lactate].

Conclusions:

The results indicate that the metabolic profile of amateur boxing is predominantly aerobic. They also highlight the importance of a highly developed aerobic capacity as a prerequisite of a high activity rate during rounds and recovery of the high-energy phosphate system during breaks as interrelated requirements of successful boxing.

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Emmanuel Van Praagh

This review summarizes the research relating anaerobic function to growth among children and adolescents. Pediatric practitioners and scientists are always struck by the impressive accumulation of results relating to the cardiopulmonary system. However, anaerobic fitness has received much less research attention. This is surprising, considering that high-intensity exercises lasting only a few seconds is a more “natural” pattern during growth than prolonged low-intensity exercises. In anaerobic tasks or sport events such as sprint running, sprint swimming, sprint cycling, jumping, or throwing, the child’s performance is distinctly lower than that of the adult. This partly reflects the child’s lesser ability to generate mechanical energy from chemical energy sources during short-term intensive work or exercise. Because both intramuscular high energy phosphate kinetics and muscle cross-section vary during growth and maturation, this review examines some developmental aspects of energetic- and mechanical factors involved in anaerobic performance. Anaerobic muscle function and performance are quantitative traits influenced by several determinants such as genetic factors, age and gender, muscle fiber characteristics, hormonal and training factors. Because of ethical and methodological constraints when investigating healthy children, this review also includes fundamental work done on some animal models.

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Gary J. Slater, Jennifer Sygo and Majke Jorgensen

discussed in detail elsewhere ( Peeling et al., 2019 ). Table 5 Ergogenic Aids of Potential Benefit for Sprinters and Sprint Hurdlers Supplement name Details a Event(s) Training Competition References Creatine monohydrate Aids in rapid rephosphorylation of high-energy phosphates and shortens muscle

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Yongming Li, Margot Niessen, Xiaoping Chen and Ulrich Hartmann

-5687(99)00083-3 31. di Prampero PE , Margaria R . Relationship between O 2 consumption, high energy phosphates and the kinetics of the O 2 debt in exercise . Pflugers Arch. 1968 ; 304 ( 1 ): 11 – 19 . PubMed doi:10.1007/BF00586714 10.1007/BF00586714

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Erin Calaine Inglis, Danilo Iannetta, Daniel A. Keir and Juan M. Murias

The highest rate of muscle metabolism that can be maintained by the oxidative system in steady-state conditions without continual blood lactate accumulation and progressive depletion of high-energy phosphates sets the upper limit of tolerable intensity. Identification of this “critical intensity

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Campbell Menzies, Michael Wood, Joel Thomas, Aaron Hengist, Jean-Philippe Walhin, Robbie Jones, Kostas Tsintzas, Javier T. Gonzalez and James A. Betts

—Endocrinology and Metabolism, 309 ( 12 ), E1032 – E1039 . PubMed ID: 26487008 doi: 10.1152/ajpendo.00376.2015 Harris , R.C. , Hultman , E. , & Nordesjö , L.O. ( 1974 ). Glycogen, glycolytic intermediates and high-energy phosphates determined in biopsy samples of musculus quadriceps femoris of man at

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David Giles, Joel B. Chidley, Nicola Taylor, Ollie Torr, Josh Hadley, Tom Randall and Simon Fryer

completed above CP is termed as W ′ (often described as the “energy store” component). 6 While CP is limited by the availability of oxidative substrates (glycogen), hyperthermia, and central fatigue, W ′ is limited by progressive depletion of high-energy phosphates and accumulation of metabolites

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Brian Killinger, Jakob D. Lauver, Luke Donovan and John Goetschius

. Effects of low-load resistance exercise with blood flow restriction on high-energy phosphate metabolism and oxygenation level in skeletal muscle . Interv Med Appl Sci . 2017 ; 9 ( 2 ): 67 – 75 . PubMed ID: 28932500 doi: 10.1556/1646.9.2017.2.16 28932500 28. Suga T , Okita K , Morita N , et