You train hard, you want to recover optimally, but there are few proven recovery mechanisms out there (aside from proper nutrition). But are there ways of preventing muscle soreness by avoiding overtraining entirely?
Heart rate gives you a good indication of how hard you are working but fails to provide an upper limit, which if exceeded would result in severe muscle soreness. This limit is referred to as the lactate threshold. This is the point at which your body can no longer supply oxygen to your muscles as quickly as it is being utilised. This creates an oxygen deficit and results in the accumulation of lactic acid. It also indicates the pace that you can maintain for a prolonged period of time, a vital statistic for any athlete. It is tested by running on a treadmill and progressively increasing the speed. Blood samples are taken every three minutes. Your lactate concentrations are plotted on a graph of speed against lactate.
Current wearable tech cannot exploit this statistic as it requires invasive techniques to measure it. If a non-invasive solution were found it would revolutionise the wearable tech market and allow athletes to customise exercise routines to their specific performance abilities.
Preventing Muscle Soreness
From my research I have found three possible ways of non-invasively measuring lactate threshold in active athletes. Near-Infrared Spectroscopy (NIRS), Pulse Oximetry & Reverse Iontophoresis. These mechanisms are not currently being utilised in this field but theoretically the technology could be transferred to this application.
Near-Infrared Spectroscopy (NIRS)
Near-infrared spectroscopy (NIRS) is a technique used to determine the quantity of a compound in a sample by emitting near infrared radiation and measuring the amount it gets back. It works because chemical compounds absorb varying amounts of radiation. NIRS does not directly measure lactate levels but can non-invasively measure oxygen saturation (SVO2). In theory it could be used to indirectly determine your lactate threshold because as lactic acid builds in the muscle, oxygen decreases. If the relationship between the two is known, the lactate threshold can be determined. A study in 1997 concluded that their “results validate the use of NIRS as an alternative non-invasive method for detecting VT (ventilator threshold) during cycle exercise in healthy subjects” (Bhambhani et al, 1997). This has been backed up by more recent research finding that “NIRS determination of StO2 is a non-invasive technique that is comparable with HLa (blood lactate concentration) in determining maximal steady state intensity and therefore appropriate for use in determining exercise training intensity” (Snyder and Parmenter, 2009).
This technology has not yet been utilised in a commercial product to monitor an athlete’s lactate threshold. The technology has recently been compressed into much smaller devices. Hand held NIRS devices are now common in the medical profession. This development would make its integration into a fitness product much easier.
Pulse Oximetry is a non-invasive method for monitoring a person’s O2 saturation. A probe (attached to your finger) uses light to measure how much oxygen is in the blood. There are numerous papers that have studied the accuracy of pulse oximetry on inactive patients and all conclude that “accurate determinations of Spo2 can be made with pulse oximetry” (Hughes et al, 1996). However no research has been completed on its ability to capture the same information during exercise. This is probably due to the readings being dependant on the patient being relatively inactive. A study in 2002 concluded that “new improvements in pulse oximeter technology have resulted in significantly better accuracy and reliability during patient motion” (Barker 2002).
Reverse Iontophoresis involves the passage of current across the skin in order to extract molecules from the body for further investigation or measurement. It is most commonly used to monitor glucose levels. A study in 2008 set out to determine if Reverse Iontophoresis could be used to measure lactate levels. It concluded that “it may be possible to non-invasively monitor the blood lactate levels using Reverse Iontophoresis” (Ching and Connolly, 2008a). Another study by the same group was conducted later that year and was successful in simultaneously extracting glucose & lactate using Reverse Iontophoresis (Ching and Connolly, 2008b).
Whilst this research was conducted by the same individuals and is the only experiment of its kind, the use of Reverse Iontophoresis for the extraction of lactate does show potential. The technology has been around for some time, but it has only recently occurred to people that it could be used for this particular application. As such, its ability to extract lactate has only recently been tested and requires further investigation. From these findings developing a fitness tracker around the premise of Reverse Intophoresis would be a possibility.
Hopefully someone reads this and gets cracking on an amazing new wearable tech product.