Skeletal muscle oxygenation response during training/assessments can give great insights to how the body is responding to the stimulus it is encountering. Over the past posts I have outlined how Moxy can be used to Autoregulate Sprint Interval Training and Strength Training, in this post I want to detail a Strength Assessment used/created by Evan Peikon at Training Think Tank to determine the best rep ranges for strength and hypertrophy based on your individual physiology using Moxy. The goal. The goal of the strength assessment is to evaluate where different occlusion trends are occurring. By honing in on what intensity an athletes’ body shifts from compression, to venous, and venous to arterial occlusion, you can better understand which weight ranges will most likely provide the physiologic adaptations that are being pursued.
Topics: strength training
Near-infrared spectroscopy (NIRS) is a powerful non-invasive tool that allows researchers to measure, in real-time, the changes in oxygen dynamics in a myriad of tissues during a variety of interventions from sitting to exercising. One of them most useful functions of NIRS is its utility in measuring skeletal muscle oxidative capacity. This technique has even been validated against phosphorus magnetic resonance spectroscopy (P-MRS) and high resolution respirometry (HRR) which are considered the gold-standard measurements for mitochondrial function. In both of the above studies the NIRS technique, described in detail below, was shown to be significantly correlated to each gold-standard measure (r > .88, p < 0.0001) and (r = 0.61 – 0.74, p < 0.01), respectively. Very briefly, to measure skeletal muscle oxidative capacity, a seated participant contracts their muscle (to provide a metabolic stimulus), then undergoes a series of 5-15 rapid cuff inflations, from a blood pressure cuff located proximal to the area of interrogation. Upon completion the cuff/s are inflated above systolic blood pressure for 3-5 minutes in order to normalize the NIRS signal. Finally, the slope of each cuff is measured, plotted, and fit to a monoexponential curve allowing for the determination of the NIRS rate constant, k, which is the value used as a surrogate for skeletal muscle oxidative capacity.
NIRS in Research. Near-infrared spectroscopy (NIRS) is a relatively new technology that has shown utility for many different non-invasive protocols for physiologic experimentation. Essentially, NIRS technology monitors changes in capillary oxygenation values by measuring the intensity of light (600-1000nm) after it passes through biological tissue, (i.e. skeletal muscle). The amount of light that is absorbed by a tissue depends mainly on the amount of oxygen that is bound to the chromophores, hemoglobin and myoglobin, underneath the sensor. Therefore, by measuring dynamic changes in the amount of light that passes through a tissue, researchers are able to get an idea of oxygen consumption within the tissue underneath the sensor.
While science does a great job of measuring the statistical norms of a population, the individual physiologic response to training must be taken into account in order to maximize an athlete’s performance potential. Training autoregulation is the concept that training should be monitored and manipulated on a daily basis, based on the individual physiologic responses of the athlete. In the last blog post I introduced the concept of autoregulation and how monitoring skeletal muscle oxygenation levels via NIRS could provide useful insights to how an athlete is coping with a workout. In the next couple of posts I want to walk through the analysis/real-time monitoring of an athlete completing a repeated sprint style workout, and a lunge based body weight strength circuit.
Scientists and coaches have long been searching for the perfect interval workout that pushes the athlete hard enough to elicit a specific adaptation while keeping them healthy enough to continue to train consistently. Such studies have resulted in the creation of guidelines for set and rep schemes for both strength and endurance training aimed at targeting specific adaptations. While this research has gleaned many generalizable rules, these rules have a tendency to fall apart when applied purely on an individual basis. Even something as simple as hypertrophy training (3-5 sets of 8-12 reps) does not always elicit the mass gain it promises. Speaking from experience, it’s extremely frustrating to complete prescribed workouts, with what seems like adequate stimulus, without gaining the benefits that are touted.
Over the last few blog posts, I have outlined how to Complete and Analyze a 5-1-5 Assessment. Briefly, a 5-1-5 assessment consists of progressively harder load steps where 5 minutes of work are followed by 1 minute of complete rest, then repeated. After the load is repeated twice it is increased until the athlete cannot finish a load or has completed sufficient work to gain enough information about their physiology. Using this data one of three major physiological limiters can be identified.
The last blog post discussed how to complete a 5-1-5 Assessment to evaluate which system: cardiac, pulmonary, or muscle oxidative capacity was most limiting to an athlete’s performance. In this post I will detail how to interpret the data to determine which system is most limiting. Upon completion of a 5-1-5 assessment, 2-3 graphs will need to be analyzed. 1) A total hemoglobin (THb) response graph which indicates how much blood is present underneath the sensor and 2) A muscle oxygen saturation (SmO2) response graph which indicates how much hemoglobin is oxygenated in the capillaries under the sensor. Optional: a third graph with heart rate response. Its typically more helpful to have the power/speed step graph overlaid with each graph to know when the power/speed is changing. Limitations are typically identified by trends in the THb and SmO2 response curves rather than by looking purely at the number values presented from the data. These trends help to identify the underlying physiology which then sheds light on the limitations being experienced during this assessment.
Purpose:The purpose of most physiologic testing is to find maximal or threshold values in order to better predict or dictate an athlete’s potential for performance. However, things like VO2max, the maximal amount of oxygen an athlete can uptake and utilize, is only predictive of performance across wide ranges of athlete prowess (Levine 2008). Determining threshold values, the point at which global-body homeostasis can no longer be maintained, may lend more credence to predicting an athlete’s performance (Heuberger et al. 2018) but in terms of dictating training, it is only a starting point. Determining threshold values allows for the simplification of training by creating training zones. However, it does not describe how the body is being limited during exercise. Endurance performance is primarily aerobic, therefore any process in which oxygen is up taken, transported, delivered, or consumed can be limiting to an athlete’s performance. There are three major systems that assist in aerobic metabolism, the pulmonary, cardiovascular, and skeletal muscle. Because of the inherent limitations with current testing protocols, the 5-1-5 Assessment was created. This assessment was designed to identify the greatest limiter (lungs, heart, or muscle) of an athlete’s physiology.
In the last few blog posts I identified a significant right left quad oxygenation imbalance during both cycling and stair climbing. In order to legitimately test the extent of these imbalances, I recently completed a standard 4-1-4 assessment using my stationary cycling power meter. Briefly, a 4-1-4 assessment consists of one load (i.e. 200W) of 4 minutes on/1 minute off/4 minutes on, then the load is increased. This pattern is repeated until the athlete cannot finish one of the 4 minute sub-stages.