Matthew J. Rogatzki

Lactate is always the end product of glycolysis

Through much of the history of metabolism, lactate (La−) has been considered merely a dead-end waste product during periods of dysoxia. Congruently, the end product of glycolysis has been viewed dichotomously: pyruvate in the presence of adequate oxygenation, La− in the absence of adequate oxygenation. In contrast, given the near-equilibrium nature of the lactate dehydrogenase (LDH) reaction and that LDH has a much higher activity than the putative regulatory enzymes of the glycolytic and oxidative pathways, we contend that La− is always the end product of glycolysis. Cellular La− accumulation, as opposed to flux, is dependent on (1) the rate of glycolysis, (2) oxidative enzyme activity, (3) cellular O2 level, and (4) the net rate of La− transport into (influx) or out of (efflux) the cell. For intracellular metabolism, we reintroduce the Cytosol-to-Mitochondria Lactate Shuttle. Our proposition, analogous to the phosphocreatine shuttle, purports that pyruvate, NAD+, NADH, and La− are held uniformly near equilibrium throughout the cell cytosol due to the high activity of LDH. La− is always the end product of glycolysis and represents the primary diffusing species capable of spatially linking glycolysis to oxidative phosphorylation.

Slowed muscle oxygen uptake kinetics with raised metabolism are not dependent on blood flow or recruitment dynamics.

A slow adjustment of skeletal muscle oxygen uptake ( V̇O2 ) to produce energy during exercise predisposes to early fatigue. In human studies, V̇O2 kinetics are slow when exercise is initiated from an elevated baseline; this is proposed to reflect slow blood flow regulation and/or recruitment of muscle fibres containing few mitochondria. To investigate this, we measured V̇O2 kinetics in canine muscle, with experimental control over muscle activation and blood flow. We found that V̇O2 kinetics remained slow when contractions were initiated from an elevated baseline despite experimentally increased blood flow and uniform fibre activation. These data challenge our current understanding of the control of muscle V̇O2 and demand consideration of new alternative mediators for V̇O2 control.

Peak Muscle Activation, Joint Kinematics, and Kinetics During Elliptical and Stepping Movement Pattern on a Precor Adaptive Motion Trainer

Kinematic, kinetic, and electromyography data were collected from the biceps femoris, rectus femoris (RF), gluteus maximus, and erector spinae (ES) during a step and elliptical exercise at a standardized workload with no hand use. Findings depicted 95% greater ankle plantar flexion (p = .01), 29% more knee extension (p = .003), 101% higher peak knee flexor moments (p < .001), 54% greater hip extensor moments (p < .001), 268% greater anterior joint reaction force (p = .009), 37% more RF activation (p < .001), and 200% more ES activation (p < .001) for the elliptical motion. Sixteen percent more hip flexion (p < .001), 42% higher knee extensor moments (p < .001), and 54% greater hip flexor moments (p = .041) occurred during the step motion. Biomechanical differences between motions should be considered when planning an exercise regimen.

Biomarkers of brain injury following an American football game: A pilot study

The goals of this study were to determine if the biomarkers of head injury, NSE and S100B, increased in serum following an American football game. Serum creatine kinase (CK) and cortisol levels were also measured to determine muscle damage and stress caused by the football game. NSE, S100B, CK, and cortisol were measured in the serum of 17 football players before and after a collegiate junior varsity football game. No head injuries were reported by the players, athletic training staff, or coaches yet both NSE (Pre-game: 7.0 μg•L–1 ± 2.2 versus Post-game: 13.1 μg•L–1 ± 7.0, P <0.001) and S100B (Pre-game: 0.013 μg•L–1 ± 0.012 versus Post-game: 0.069 μg•L–1 ± 0.036, P <0.001) increased significantly. Neither CK (Pre-game: 90.5 U•L–1 ± 41.9 versus Post-game: 120.2 U•L–1 ± 62.7, P = 0.116) nor cortisol (Pre-game: 369.2 nmoles•L-1 ± 159.8 versus Post-game: 353.0 nmoles•L–1 ± 170.5, P = 0.349) increased significantly following the football game. There was little correlation found between S100B and body mass (R2 = 0.029) or CK (R2 = 0.352) levels. Although serum NSE and S100B increase as a result of playing in an American football game, the values are similar to or lower than levels found following competition in other contact and non-contact sports. Furthermore, the lack of correlation between S100B and body mass or CK indicates that S100B increases independent of body mass or muscle injury.

Blood Ammonium and Lactate Accumulation Response to Different Training Protocols Using the Parallel Squat Exercise

Abstract Rogatzki, MJ, Wright, GA, Mikat, RP, and Brice, AG. Blood Ammonium and Lactate Accumulation Response to Different Training Protocols Using the Parallel Squat Exercise. J Strength Cond Res 28(4): 1113–1118, 2014—Three parallel squat protocols with equal total work volume were used to determine the metabolic response of resistance exercise with different practical training protocols combining program variables in the way that they are typically prescribed in field. Sixteen men able to back squat 1.5 times their body weight participated in the study. Individualized muscular endurance (ME), strength (STR), and hypertrophy (HYP) squat workouts were developed based on a 1 repetition maximum back squat. Each protocol was performed 3–7 days apart in random order. Venous blood was obtained after 5 minutes of seated rest both before and after each workout for ammonium and lactate analysis. The ME protocol (79.8 &mgr;M [SD = 45.4], 95% confidence interval [CI]: 55.7–104.0) produced a greater change of plasma ammonium than both the HYP (45.3 &mgr;M [SD = 34.5], 95% CI: 26.9–63.6, p = 0.017) and STR (31.7 &mgr;M [SD = 52.3], 95% CI: 3.9–59.6, p = 0.006) protocols. Change of blood lactate concentration from resting levels to postexercise levels was significantly different (p = 0.005) between ME (6.1 mM [SD = 2.9], 95% CI: 4.6–7.7) and STR (3.9 mM [SD = 2.5], 95% CI: 2.6–5.2) protocols. The main finding of this study is that blood ammonium and lactate seem to accumulate in response to an increasing number of repetitions with decreasing rest time between sets. As consequence, a greater number of repetitions should be added to a resistance workout, along with a shorter rest time between sets when training for events that induce a large metabolic load. The metabolic accumulation associated with high repetition exercise may represent the need for longer recovery time between these types of workouts compared with workouts using a low number of repetitions.

Traumatic Brain Injury in Sport with Special Focus on Biomarkers of Concussion Injury

Traumatic brain injury (TBI) is typically categorized as being mild, moderate, or severe. Over the years much of the research focus has been geared toward moderate and severe TBI as these injuries are seen most often in the clinical setting. In contrast, mild TBI is more difficult to diagnose and there is inconsistency within the literature on how exactly mild TBI should be diagnosed. Even more difficult to diagnose than mild TBI is concussion injury. Concussions have been a recent and constant news headline for the past several years as evidence suggests that repeated concussive and sub-concussive impacts due to sports play, especially American football, can result in permanent brain damage. Therefore, it is the purpose of this short communication to shed light on recent research into the discovery of an objective and reliable biomarker to assess concussion injury.