Listen to your muscles when they talk to you

All athletes, at various stages of training and competition, will experience sensations of muscle soreness. In most cases, the worst symptoms of an acute bout of soreness are delayed by 24-48 hours (known as delayed onset of muscle soreness, or DOMS), typically reflecting unaccustomed loading on the muscles and subsequent muscle damage. The first time you go to the gym in a long time – or ever – you’ll know about it the next day or two with your whole body screaming at you! Or the first day out on the water wakeboarding. Or the usually “flat runner” hitting the mountains for a large dose of undulating trail running. For long distance triathletes, more so than their shorter distance counterparts, those final kilometres during the run can be torturous on the legs. Try walking down stairs the next day: “Ah, I don’t think so!”

Don’t despair, the upside to acute exercise-induced muscle damage includes the subsequent protective effects on your muscle architecture – respond and adapt.

However, many athletes lack the confidence in reading between the lines on managing soreness. Is it a transient response that is expected with a particular period of training? Is it the start of a chronic condition that may increase the risk of injury? It certainly helps athletes and coaches with planning, expectations and resilience when the fundamentals of the loading/damage process are recognised and respected.

What causes muscle damage?
Muscle fibres contract via a series of highly complex electrical, chemical and metabolic interactions, culminating in force generation and subsequent movement of paired muscle groups.
To put in perspective – during a run, the quadriceps muscles apply force to propel your legs in a forward motion (concentric contraction = muscle shortening under force), and to complete the gait cycle the hamstring lengthens to manage the external load (eccentric contraction). Together, these distinctive segments of muscle shortening and lengthening are known as the stretch-shortening cycle.

Interestingly, the greatest training strength gains are made via the eccentric contractile phase, but also, paradoxically, eccentric contractions contribute to the lion’s share of ensuing muscle damage and soreness following extensive or unaccustomed loading on the muscles.

When the triathlon segments are broken down, the eccentric contractile phases are minor during cycling and swimming, and most pronounced when running. Indeed, the eccentric loads are substantially magnified when running downhill, as the hamstring is required to “break harder” each time one foot hits the ground, given the exceedingly higher external load that goes with a negative gradient. As such, there are substantial changes to properties inside muscle cells that affect muscle structure, integrity and function via protein leakage into the circulation and pronounced inflammatory responses. These changes reduce the muscle ability to produce force – accelerate time taken to fatigue.

Several studies have demonstrated impairment to running (Marcora &, Bosio, 2007) and cycling (Twist & Eston, 2009) time trial performance following eccentric exercise. There is also compelling evidence that exercise-induced muscle damage reduces muscle glycogen content and impairs glycogen resynthesis (Asp et al., 1998). Together, these metabolic disturbances are considered a major disadvantage to triathletes, who heavily rely on oxidative metabolism to preserve performance.

What are the key factors that positively affect the magnitude of muscle soreness?
Previous training history – exposure to a “manageable amount” of eccentric loading via strength training, plyometrics, prolonged endurance exercise (particularly running) and downhill running.
Gender – oestrogen has a protective effect on muscle integrity during exercise (Williams et al., 2015; Enns &, 2010). We have also monitored male and female athletes in our clinic, over several years, undertaking very similar training programs, and noted lower production of enzymes and inflammatory markers in women. Perhaps the oestrogen phenomenon goes some way to explaining why females are more competitive with males during long endurance events?

What are the key factors that negatively affect the magnitude of muscle soreness?
Genetics – ACTN3 X-allele carriers are exposed to greater levels of muscle damage.
DNA damage – high incidence of inflammatory processes following repeated muscle damage (incomplete recovery) may provoke DNA changes – although more research is required.
Incomplete recovery – long distance triathlon provokes a significant reliance on muscle glycogen. Resynthesis of glycogen is impaired by the presence of muscle damage. Therefore, a return to training or competition too quickly may alter metabolic responses that are mandatory to perform well.

Conditioning your muscles to increase resilience to the demands of training and competition
The benefits of strength training have been highlighted numerous times during recent triathlon performance editorials. Conditioning your muscles with regular strategic strength training will improve resilience to the debilitating effects of muscle damage. A good starting point should include squats, calf-raises and deadlifts – 3-4 sets, 8-10 reps. For the most part, combining concentric and eccentric phases of a movement (e.g., squats – downward and upward phase) will promote effective adaptations. Then if you are really keen and want to take strength adaptations a step further, designated sessions of eccentric phase only will have more pronounced effects (e.g., squat – downward phase only; calf raise – downward phase on a step, et al.). However, eccentric phase training, particularly with squats, is somewhat labour intensive and requires one to two spotting buddies.

Include strategic periods of downhill running. An effective way to start is integrating undulating courses if you are otherwise a regular flat-terrain runner. The analogy of graduating volume, velocity and frequency of downhill running is much the same as building your regular training. Too much, too soon will increase your risk of soft tissue injury. Starting with shorter downhill intervals, and building to longer efforts will expose leg muscles to protective features.

Recovery from muscle damage
Consider the appropriate time frame to recover from training or competition induced muscle damage.

Excessive intervention (i.e., ice therapy, electrical stimulation, non-steroidal anti- inflammatory meds) during a build phase can interfere with important adaptations. Adequate rest between “eccentric biased” training is usually appropriate.

However, following arduous exertion, such as an Ironman triathlon, more care is required before ramping up training and the next competition. A number of post-competition triathlon studies have identified significant changes in blood markers associated with muscle damage, and reduced muscle function.

During a study by Neubauer and colleagues (2008), 42 well-trained male triathletes were monitored closely for 19 days to evaluate recovery. As expected, substantial hormonal, enzymatic, inflammatory and immune system disturbances were evident one day post. After five days, most of these disturbances were reduced. However, they were still well above normal levels expected in recovery. After 19-days, a number of muscle damage and inflammatory markers were still elevated above initial pre-race baseline, which reflects incomplete muscle recovery. These findings do not suggest a complete rest for three weeks is required after an Ironman triathlon, but do suggest that metabolic and anatomical loads should be carefully considered.

Key tests to consider:
Blood tests don’t always hold the answers. However, baseline and post event evaluation of immunological, inflammatory, metabolic, and haematological and muscle damage markers will shed light on athlete specific responses.

Muscle power and strength tests provide insight into leg muscle integrity. A simple vertical jump test is reflective of a muscles contractile integrity and recovery. Strength tests can include a series of squats, or a more sophisticated maximal force production test on a Cybex dynamometer. Put simply, if you are unable to replicate pre-event results, your muscles need more time to recover.


Marcora SM, Bosio A (Scand J Med Sci Sports, 2007). Effect of exercise-induced muscle damage on endurance running performance in humans

Twist C & Eston RG (Eur J Appl Physiol, 2009).
The effect of exercise-induced muscle damage on perceived exertion and cycling endurance performance.

Asp S; et al. (J Physiol, 1998). Exercise metabolism
in human skeletal muscle exposed to prior
eccentric exercise.

Williams T et al. (Biol Sport. 2015). The effect of oestrogen on muscle damage biomarkers following prolonged aerobic exercise in eumenorrheic women.

Enns DL & Tiidus PM (Sports Med. 2010). The influence of oestrogen on skeletal muscle: sex matters.

Neubauer O, et al. (Eur J Appl Physiol. 2008). Recovery after an Ironman triathlon: sustained inflammatory responses and muscular stress.



Simon Sostaric

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