Concurrent Strength and Endurance Training (S&E)
As a continuation from my last post about improving strength to increase sustainable power through resistance exercise with weights… this post delves into more of the actual training practicalities involved. Performing strength and endurance training promotes a greater volume of Type IIA, more fatigue resistant, high force muscle fibers, which can take on more aerobic characteristics such as slow twitch Type I. These provide a better exercise economy and efficiency for the cyclist. Think less fatigue and more consistent power at the end of a 160km ride, while everyone else is suffering, that’s what it’s about. Recruiting more functionally aerobic muscle mass or density will mean removing the greater stress on the heart and lungs, which in turn means being much more comfortable on demanding terrain, duration and race scenarios at all levels of cycling, and very achievable. However the development of a higher level of endurance, prohibits or negates the maintenance of muscle mass and strength as intense aerobic exercise has a catabolic effect.
I will touch on how aerobic conditioning can and should be blended in with strength training to achieve better performance on the bike, and also the nutritional strategies which can help achieve that. This is known in the field of sports science as the concurrent training of divergent exercise, and isn’t such a new concept. Even though, there is limited understanding about the interplay between strength and endurance sessions. Divergent exercise basically means that endurance training can interfere with achieving maximal strength gains, which are to some degree mutually exclusive. This may explain why many individuals training programmes aren’t designed optimally to maximise productive training, which may lead to demotivation and wasted sessions both in the gym and on the bike. However there are huge gains to be made every winter, while your ride mates slog it out in wet or icey conditions just to have a lacklustre season ahead of them. These strength gains ultimately show themselves during a well targeted event or planned peak performances.
Studies in strength and endurance training individuals (training 40min/day 5days/ week with 2hr recovery in between) clearly demonstrate that strength gains, (as indicated by the 1 Repetition Maximum squat) are significantly less after 8 weeks, than those who undertake strength training alone with a similar format of sessions. Concurrent strength and endurance training can result in twice as much strength, compared to endurance training by itself and a negligible increase in body mass (lean muscle, less fat) is largely offset by the improvement in power-to-weight. Other studies have shown that concurrent training can result in as good maximal force and cross-sectional muscle area (CSA) as strength training, while VO2peak and endurance improved as much as with interval training, which confuses the picture somewhat, but still very much in the favour of concurrent training and is a big plus for justification of conducting concurrent training.
The mechanism of interaction of the two types of training is not well understood, although some cellular pathways have been identified. Mechanical and hormonal activation of skeletal muscle interacts (a protein called mTor, mammalian target of Rapamycin, a bit biochemical…and nothing to do with MAMILS btw) with known endurance adaptation pathways, through metabolic stress proteins AMPK and PGC1-alpha and molecular interference within the muscle to blunt the training effect. Depending on the objective of the training, reduced strength gains is detrimental to the individual, but also the rate of adaptation may be limited over the number of weeks of training.
Neuromuscular fatigue (such as Delayed Onset Muscle Soreness or DOMS) can be quickly developed, but it may also be depletion of energy stores by endurance exercise which restrict muscle hypertrophy and have a significant interference of effect on performance. The illustration demonstrates how an interaction may occur between substrate depletion and fatigue on the ability to recover and adapt through hypertrophy of muscle. This may be mediated through reduced mechanical force production or lack of muscle protein synthesis (MPS).
Blending sessions, how practical?
The practicalities of S&E training can be summarised by the need to prioritise either endurance (long duration, low force) or resistance (short duration, high force) sessions, which is generally dictated in periodisation programmes by low endurance volume to accommodate an effective frequency of resistance sessions bracketed by interval training and longer endurance ride sessions to create stress, overload and aerobic conditioning. The need to recruit muscle fiber neuromuscularly (engage muscle through nervous stimulation before visible increase in lean mass, which can take up to 8 weeks) and make them bigger is important, before making them less fatigable and ultimately transforming them to fatigue resistant types (an efficient muscle is usually smaller than it was during hypertrophy/ maximum force development).
More practically, the responses to concurrent exercise is dependent on training status, the order of concurrent exercise regime, and the mode and time course involved. Performing endurance training prior to resistance exercise in a concurrent model may have limited detrimental effects on anabolic signalling or adaptive growth.
Factors to consider
- FREQUENCY OF TRAINING 2/3 endurance or strength sessions/ week
- SEQUENCING am endurance, pm resistance (strength)?
- TYPE OF ENDURANCE
To schedule in the sessions appropriately, working on concurrent build or recovery, periodisation and block training is the best approach to consider, of which different formats are available for the needs of different individuals.
When focusing on strength and hypertrophy, 3 endurance sessions a week is sufficient. If greater power adaptations are needed i.e. for sprinting or track disciplines, then 2 sessions are adequate. For example, this may include a long ride at mid-tempo pace with a spread of above threshold efforts, and a pyramid style interval session working on anaerobic or VO2peak duration/intensity depending on the phase of the resistance training, ADAPTATION, HYPERTROPHY, STRENGTH, POWER, MUSCULAR ENDURANCE (short and long term) & MAINTENANCE.
It is possible to perform divergent exercise sessions on the same day without compromising the adaptation process, and in some cases is very beneficial for highly motivated athletes near the top of their game. Recovery duration of >6hrs is optimal between sessions. Practically, endurance training should precede resistance training by at least 3hrs if performed that way around. The good news is that cycling at above threshold intensities, fortunately has less interference (than running at VO2peak) where strength and hypertrophy are priority. The optimal duration of sessions- greater than 50/60min endurance session, is detrimental strength gains though.
What about nutrition?
Intensity can play an important role as aerobic exercise increases protein breakdown and high cortisol levels, causing a negative net protein balance and muscle wasting when performed repetitively or chronically. Higher intensity sprint intervals can accentuate strength and hypertrophy gains more quickly with strength training, assisting transformation of Type IIx to Type IIa, but also maintain maximal strength characteristics. Older athletes can experience varying degrees of sarcopenia through disuse and/or decline in muscle function, so concurrent strength and endurance training with high intensity intervals is an excellent way of improving anaerobic capacity and increasing sustainable aerobic intensity (aka lactate threshold). This approach is also thought to reduce the decline in VO2peak in master athletes.
I hope to summarise the role that nutrition and particularly protein plays in improving both resistance and endurance, although I will provide some more details in my next posts on Recovery and Adaptation, and the Science of Protein.
More briefly, understanding the nutritional requirements of concurrent training is so far quite limited, and is reliant on an overlap of both endurance and resistance exercise, individually. Although much more is known about the role of protein after just strength exercise sessions. Energy restriction in skeletal muscle appears to amplify the endurance training signalling environment, whereas a positive energy balance is optimal to maximise the anabolic environment post-resistance exercise.
Exercise in the fasted state increases both the synthesis and breakdown (i.e. “turnover”) of muscle protein with the difference between these processes determining the net protein balance (i.e. synthesis – breakdown). It is well known that the ingestion of essential amino acids enhances MPS and net protein balance after exercise (Tipton et al., 1999). However, the stimulatory effect of amino acids on MPS is uninfluenced by the co-ingestion of carbohydrate (Glynn et al., 2010; Staples et al., 2011), demonstrating that dietary protein is the primary nutritional factor regulating skeletal muscle remodelling after exercise and, in the case of resistance exercise, can enhance training-induced muscle growth (Burd et al., 2009).
Consumption of carbohydrate immediately post-exercise reduces the breakdown of muscle protein, to facilitate muscle protein synthesis (MPS). If additional carbohydrates are not taken then proteins from muscle are used in the repair process. Increased carbohydrate can protect against elevated cortisol levels which can increase muscle protein breakdown. Therefore, taking high GI carbohydrates which readily stimulate insulin, an anabolic hormone with positive effects on MPS, will help support muscle tissue repair and growth. For a moderately fit cyclist with average performance and physiological characteristics (22.5% efficiency), following a relatively intense ride session of 3hrs (200watts average) would need to consume 500-600g of carbohydrate post-ride to replenish glycogen stores.
When to take protein?
In general, there are three occasions in which athletes may take in nutrients to facilitate their training and recovery: before, during and after exercise. These clear distinctions between eating occasions are not always evident for athletes who train on consecutive days or, more importantly, multiple times per day, as would be the case with many concurrent athletes.
PRIOR – less emphasis
- The digestion and absorption of high quality dietary protein typically results in peak blood amino acid concentrations occurring within 1 h after ingestion and being sustained for up to 2–3 h, although this depends on the protein type, energy density and food matrix of the nutrition.
- MPS is generally depressed during muscle contraction due to the shunting of cellular energy away from non-essential energy-consuming processes such as protein remodelling (Atherton & Rennie, 2006). This lessens the importance of pre-exercise protein ingestion for the greater muscle remodelling and adaptive process.
Therefore, athletes performing brief (e.g. ≤1 h) exercise bouts would arguably obtain a greater benefit from a pre-exercise feeding strategy that would prioritise fuelling with carbohydrate.
DURING – irrelevant?
- Aerobic exercise is associated with an enhanced metabolism of amino acids (especially the branched-chain amino acids) (Millward, Bowtell, Pacy, & Rennie, 1994) that arise from the catabolism (degradation) of skeletal muscle protein, which ultimately results in a negative muscle and whole body protein balance during exercise (Howarth et al., 2010).
- For athletes who perform relatively long (e.g. ≥1.5 h) bouts or multiple endurance training sessions per day, the inclusion of protein during their workout may help limit the endogenous (internal storage) use of amino acids as a source of fuel and improve whole body protein balance during exercise (Beelen et al., 2011).
- It is presently unclear, however, as to what extent protein intake could improve muscle protein remodelling or net protein balance during a bout of endurance exercise (Beelen et al., 2011), given the general suppression of anabolic pathways during periods of high contraction/ ATP demand (e.g. muscle contraction; Atherton & Rennie, 2006).
Therefore, athletes who perform long resistance training sessions and/or who train concurrently after their endurance exercise sessions may benefit from the co-ingestion of dietary protein during their training bouts, which could act to prime the muscles for protein synthesis straight after exercise.
FOLLOWING – More emphasis
As mentioned, recovery is critical to the success for a concurrent strength and endurance periodisation programme, hence increasing glycogen availability through carbohydrate intake is very important along with adequate rest between sessions and should be priority fuelling for endurance sessions. Glycogen re-synthesis is biphasic, meaning the first stage is Insulin independent (30-60min), and the second stage, which is Insulin dependent (after 90 min – hours) and so intake can be divided appropriately, i.e. more acutely and then more chronically after a session.
However, athletes aiming to maximise recovery from each training bout would benefit from greater post-exercise protein ingestion, as demonstrated by recent ingested protein dose–response studies (Moore, Robinson, et al., 2009; Witard et al., 2014). Therefore, the ‘optimal’ protein ingestion (i.e. one that maximises MPS yet minimises irreversible amino acid metabolism) would be approx. 20 g (or the equivalent of about 0.25 g/kg) of high-quality protein (such as whey protein).
- Following exercise protein ingestion immediately after exercise unquestionably enhances MPS and net protein balance in young adults after all forms of exercise (Burd et al., 2009; Moore et al., 2014).
- Resistance exercise has been shown to enhance the sensitivity of skeletal muscle to dietary protein for up to 24 hours, meaning that protein consumed at any time within this extended ‘window of opportunity’ will contribute to enhanced muscle remodelling and adaptation (Burd et al., 2011). This may explain, in part, the recent suggestion that the timing of protein intake around a resistance exercise session (i.e. ±2 h) plays a limited role in the ability to augment training-induced gains in muscle mass or strength primarily in novice athletes (Schoenfeld, Aragon, & Krieger, 2013).
- Resistance-trained individuals may have a relatively abbreviated ‘window of opportunity’, given that rates of MPS are enhanced by protein ingestion 4 h, but not 28 h, after an acute bout of resistance exercise (Tang, Perco, Moore, Wilkinson, & Phillips, 2008).
- Compared to immediately post-exercise, delaying protein ingestion by as little as 3 h after constant load aerobic exercise markedly blunts its anabolic effects as demonstrated by a lack of stimulation of MPS (Levenhagen et al., 2001).
Therefore, it would be prudent for athletes aiming to rapidly initiate muscle remodelling and recovery to consume dietary protein as soon as possible after an exercise bout, regardless of training type.
- Aside from the immediate post-exercise feeding period, the pattern of protein ingestion outside of this early (i.e. < 3 h) recovery period can also impact the extent of muscle protein remodelling. For instance, the repeated ingestion of 20 g of protein [i.e. an “optimal” amount for the stimulation of MPS (Moore, Robinson, et al., 2009; Witard et al., 2014)] every 3 h over 12 h supported greater rates of myofibrillar protein synthesis and induced a more positive whole-body protein balance after a bout of resistance exercise than the identical amount (i.e. 80 g) of protein ingested as 10 g feedings every 1.5 h or 40 g feedings every 6 h (Areta et al., 2013; Moore et al., 2012).
This demonstrates that the pattern, and not merely the amount, of protein ingested can influence the efficiency of post-exercise muscle remodelling after resistance exercise. While such prolonged recovery studies have not been performed after endurance and/or concurrent exercise, it is likely that a similar feeding pattern (both of protein amount and frequency) would also support the greatest rates of MPS after these training modalities, given that 20–25 g (0.25–0.30 g protein/kg/meal) of protein has been established to saturate the protein synthetic capacity of the muscle in multiple studies at rest and after exercise (Moore, Robinson, et al., 2009; Witard et al., 2014).
- Additionally, protein consumed (40g) immediately prior to sleep has been reported to sustain greater rates of MPS during the overnight post-exercise recovery period (Res et al., 2012), which may help athletes who, due to scheduling or personal preference, must train in the evening but want to maximise their recovery.
Protein with carbohydrate?
High intensity and prolonged aerobic exercise can lead to depleted muscle glycogen stores. Consuming carbohydrate with protein (containing BCAAs) is beneficial to post-exercise recovery and rates of MPS. Increasing rates of glycogen replenshment enhances subsequent exercise performance. If muscle stores are not replaced, there are increased rates of muscle breakdown and reduced levels of recovery following exercise.
Under some circumstances, it may also be beneficial for the concurrent athlete to delay glycogen re-synthesis, allowing endurance exercise to be performed in a glycogen-depleted state (see review in this issue from Morton and Hawley). However, the payoff for this strategy may be a greater rate of muscle catabolism with low glycogen levels (Howarth et al., 2010).
- Co-ingesting protein with suboptimal doses of carbohydrate (less than 1-1.2g/kg/hour) elicits a glycogen re-synthesis response comparable to higher carbohydrate ingestion (Burke et al., 2011). This suppresses muscle protein breakdown and promotes recovery.
- Combined protein and carbohydrate ingestion could be advantageous for a concurrent training athlete looking to restore glycogen levels quickly prior to a second exercise bout or to avoid ingesting high amounts of carbohydrate. 50 -75g of quick releasing carbohydrate an exercise sessions lasting more than 1hr, and a second dose after 90min.
- Muscle glycogen re-synthesis does not increase any further after carbohydrate intake reaches 1.2/1.3 g/kg/hr. Hence co-ingestion of Protein and CHO, has no further additive effect.
It is therefore, likely that periodising protein and combined protein–carbohydrate ingestion in respect to the type/intensity of exercise during a concurrent training regime could be the most practical approach. Clearly, this topic will provide numerous avenues of experimentation for concurrent-based research in the future.
The development of a high level of endurance prohibits the maintenance of muscle mass and strength. The mechanism of interaction of the two types of training is not well understood, although some cellular pathways have been identified. More practically, the responses to concurrent exercise is dependent on training status, the order of concurrent exercise regime, and the mode and time course involved. Performing endurance training prior to resistance exercise in a concurrent model may have limited detrimental effects on anabolic signalling or adaptive growth. It is possible to perform divergent exercise sessions on the same day without compromising the adaptation process, and in some cases is very beneficial for highly motivated athletes near the top of their game. Recovery duration of >6hrs is optimal between sessions. Cycling at above threshold intensities, fortunately has less interference (than running at VO2peak) where strength and hypertrophy are priority.
The understanding of the specific protein requirements to maximise MPS after endurance exercise are at a relative infancy compared to resistance exercise (Moore et al., 2014). Nevertheless, MPS is similarly enhanced after endurance-based exercise with approx. 16–20 g of dietary protein in both untrained and trained athletes suggesting post-exercise protein requirements for skeletal muscle remodelling are likely consistent across training modalities (Moore et al., 2014). Therefore, based on currently available literature, the ‘optimal’ protein ingestion would likely be similar after endurance exercise, meaning that concurrent athletes can likely interchange dosing across the training regime.
Moreover, during periods of chronic energy restriction, such as would be encountered during voluntary weight loss or inadvertent suboptimal energy intake, protein ingestion is essential to enhance post-exercise MPS (Areta et al., 2014) and the maintenance of lean mass.
Therefore, dietary protein should be viewed as a core component of the recovery nutrition for the concurrent athlete (and especially weight restricted athletes) through its ability to enhance muscle protein remodelling.
Quick steps to optimise Strength and Endurance training:
- Perform high intensity, longer endurance sessions a minimum of 3hrs before resistance workouts to reduce biochemical interference in the muscles.
- Perform low intensity, shorter endurance sessions immediately before strength sessions to improve the endurance response to low intensity exercise at the same time increase strength gains.
- Refuel with high GI carbohydrate between high-intensity endurance training session and afternoon resistance workouts. Although avoiding carbohydrate consumption may amplify effect due to resistance training when energy is less abundant immediately prior to exercise.
- Eat easily digestible, high leucine-content protein-based meal (or Whey supplement with BCAAs) asap after resistance sessions to promote optimal muscle protein synthesis.
- Consider strength training straight after low-intensity non-depleting glycogen endurance sessions, for better endurance adaptation.
- Target 4 meals of 20g high quality protein/ day every 4 hours in a 16 hour period to maximally stimulate muscle protein synthesis throughout the day. 1.5-1.7 g/kg/day for strength and endurance training individuals.
- Extra protein has no effect on increasing glycogen storage once carbohydrate intake is optimal. 1.0-1.2g/kg/hr.
- 40g of protein before bed boosts the optimal protein intake closer to 1.5 g/kg/day (for a male)…but also maximises the synthetic response over-night, and maintaining a positive net protein balance to promote anabolic activity.