Training Load

This study was specifically aimed at profiling the BMD, BMI and BF% of female long distance runners and determining the impact of their chosen sport on the three aforementioned factors. One of the requirements for participation in the study was to have completed at least two marathon events and or an ultra-marathon running event, otherwise referred to as long distance running. Not all of the participants had completed an ultra-marathon event, but everyone had to have completed at least two marathon events in order to qualify to participate in the study.

This section first focuses on participants’ running regime, such as their weekly distances and frequencies, the number of marathon and ultra-marathon events they have completed as well as the number of running years they have accumulated. It also includes information on involvement in strength and conditioning training, for example if they engage in a strength- based program and if so, the frequency per week of that training. All of the information about their training and number of events participated in as well as the quality of their performances in these long distance events were used to determine the impact of long distance running on particularly BMD but also on their BMI and BF%.

The findings of this study indicated that the majority of the participants (n = 27) have only been running long distance events, both socially and competitively, for fewer than 11 years, according to Table 4.24 and Figure 4.3. Table 4.25 depicts that the majority of the participants (n = 24) have completed between two and 10 marathon events, (Table 4.25 and Figure 4.4), and between one and five ultra-marathon events (Figure 4.4).

Table 4.24 depicts the inferential statistics of the comparison between the two categories, namely the lower versus the higher number of long distance running years completed and how the participants in these categories compare with respect to the BMD variables, BF% and BMI. The findings depicted in Table 4.24 indicate that there are no significant differences between the mean scores for the BMD variables, BF% and BMI respectively of those who have completed fewer than 11 long distance running years and those who have completed more than 10 long distance running years, both socially and competitively.

Table 4.25 presents the inferential statistics for the comparison between the two categories of total number of completed marathon events in respect of BMD variables, BF% and BMI. The results reflected in Table 4.25 indicate that there were no significant differences found in the mean scores for BMD, BF% and BMI respectively when comparing those who have competed

Those who have participated in more than 11 marathon events have slightly greater mean Z- score ratings, and thus a better BMD for their age group and also a lower mean BF% and BMI, although these differences were not significant.

When comparing the differences in BMD, BF% and BMI respectively in relation to participation in ultra-marathons versus no participation in such events, the results in Table 4.26 indicate that there is a significant difference (p < .05; d > 0.2) between the number of completed ultra- marathons and BF% as well as BMI respectively. The mean values for BF% was significantly higher in those who have completed five or fewer ultra-marathon events (28.76 ± 5.21%) compared to those who have completed six or more ultra-marathon events (24.67 ± 6.81%). The mean value for BMI was also significantly higher in those who have completed five or fewer ultra-marathon events (23.75 ± 2.38 kg/m²) compared to those who have completed six or more ultra-marathon events (21.86 ± 2.48 kg/m²). The mean values for BMD and Z-score variables were found to be slightly higher in those who have participated in five or fewer ultra- marathon events (n = 20) compared to those who have participated in more than six ultra- marathon events (n = 20), but these differences are small and not significant.

Similarly, when comparing BMD, BF% and BMI respectively in relation to the total number of long distance events completed (marathons plus ultra-marathons) by the runners involved in this study, Table 4.27 indicates that the mean values for the femoral neck, hip total, lumbar spine and total body BMD are greater in those who have participated in fewer than 11 long distance running events in total compared to those who have participated in more than 10 long distance running events. These differences are not significant. The mean values for BF% and BMI were also greater in those who have participated in fewer than 11 long distance running events, but these differences were also insignificant.

Table 4.28 indicates the inferential statistics for the comparison between the categories for best marathon completion times in respect of the BMD variables, BF% and BMI. The findings reflected in Table 4.28 indicate that the mean value for BF% was significantly lower (p < .05; d > 2) in those who completed a marathon in under three hours and 50 minutes (23.41 ± 8.03%) compared to those who have completed a marathon in equal to or over three hours and 50 minutes (28.30 ± 4.72%). Table 4.28 indicates that those who have completed a marathon event in under three hours and 50 minutes have slightly lower mean values for BMD and BMI ratings, but these differences were not significant.

Findings by Knechtle et al. (2012:254) correlate with those of this study as reflected in Tables 4.26 and 4.28. According to Knechtle et al. (2012:254), ultra-marathon runners have a lower

BF%, which coincides with the results presented in Table 4.26, which reflect that those who completed five or fewer ultra-marathon events had a higher BF% and BMI than those who completed six or more ultra-marathon events. Knechtle et al. (2012:254) posit that an association has been found whereby completing a long distance running event in a shorter time will result in a lower BF%. The findings of the present study indicated that BF% was lower in those who completed a marathon in a shorter time, therefore, correlating to the findings of the study conducted by Knechtle et al. (2012:254).

According to research, physical activity stimulates bone formation to maintain BMD and prevent the onset of osteoporosis (Pollock et al., 2010:419; Korsten-Reck, 2011:158; Kruger et al., 2011:756; de Almeida Carvalho et al., 2014). It is recommended that load bearing exercises and resistance training be incorporated into the training regime (Burrows & Bird, 2000:282; Gibson et al., 2004:611; Pollock et al., 2010:420; Wilkin et al., 2010:205; de Almeida Carvalho et al., 2014; Abd El Mohsen et al., 2016:2579; Kim et al., 2016:2; Stunes et al., 2017:13). According to a study conducted by Marques et al. (2011:529), resistance training has a positive influence on BMD, especially at the hip.

Table 4.29 presents the inferential statistics of the comparison between the categories of average weekly running distance per year in respect of BMD variables, BF% and BMI. The runners’ average weekly running distance per year was divided into two categories, 30-50 (n = 17) and 51-100 (n = 23) km/week respectively. The runners in each of these two running distance categories were compared with each other with respect to each of the BMD ratings, as well as with the mean BMI and BF% values. Table 4.29 indicates that there is a significant difference (p < .05; d > 0.2) for the hip total Z-score with the lower average weekly running distance per year category presenting the higher value (0.81 ± 0.77 versus 0.24 ± 0.89 g/cm2_).

A significant difference (p < .05; d > 0.2) for both BF% and BMI were found with the lower average weekly running distance per year category presenting with the higher BF% (29.97 ± 6.27 versus 24.30 ± 5.31%) and BMI (24.10 ± 2.79 versus 21.85 ± 1.97 kg/m2_).

Studies conducted by Duncan et al. (2002:294), Andreoli et al. (2012:69) Selingerova et al. (2015:273) and Stiles et al. (2017:1851), indicate that physical activity influences BMD positively in that BMD is increased. Pollock et al. (2010:421) and Wentz et al. (2012:380) found that there is a negative association between the hours that are spent training within the week and a lowered BMD of the lumbar spine and the total body. According to Duncan et al. (2002:288), a positive correlation has been found between the BMD of the arm and the hours of training per week. The results of the present study as reflected in Table 4.29, support

Pollock et al. (2010:421) and Wentz et al. (2012:380), as the lumbar spine was found to have a lower BMD than the other body segments that were analysed.

According to Vorster et al. (2001:21) and Wentz et al. (2012:381), intense training over a prolonged period can cause an elevated bone turnover due to the increased bone resorption by the osteoclasts. The bone formation and resorption cycle is, therefore, affected negatively. Endurance running increases the mechanical load that is placed on the body, which protects against the loss of bone and the area of the body that is exposed to the greatest amount of stress will present the higher BMD rating (Pollock et al., 2010:420; Andreoli et al., 2012:73; Williamson, 2016:12). As per Table 4.29, the hip total Z-score was found to be significantly higher than the other body segments, which supports Pollock et al. (2010:420), Andreoli et al. (2012:73) and Williamson (2016:12) and may indicate that most of the mechanical loading occurred in the hip region.

The running season is divided into a pre-season, in-season and an off-season. Running distances and frequency increase from pre-season to in-season and then begins to decline during the off-season. The running distance per week during each running season can be found in Appendix F (Tables F.41 to F.46).

It has been found that an increase in running distance, frequency and intensity may influence the BMD rating negatively (Pollock et al., 2010:420; Benca et al., 2013:351). This is due to the increase of the mechanical loading that is placed on the body during endurance running, which can interrupt the balance between bone resorption and bone formation (Williamson, 2016:12; Wentz et al., 2012:381; Pollock et al., 2010:420; Kim et al., 2014:716). According to Burrows and Bird (2000:282), in order to maintain BMD, it is advised to run between 20 and 30 km per week for 2 to 3 for a duration of 20 to 60 minutes. The present study indicates that the higher proportion of the sample engage in an average weekly running distance of 51 to 100 km (Table 4.29) for longer than 60 minutes at a time. The runners in this study all exceeded the recommendation by Burrows and Bird (2000:282), which may have affected their BMD negatively (Pollock et al., 2010:420; Benca et al., 2013:351).

It is also recommended to incorporate physical activity such as resistance and load bearing exercises into one’s running training regime (Gibson et al., 2004:612; Wilkin et al., 2010:205; de Almeida Carvalho et al., 2014; Stunes et al., 2017:13). Physical activity can stimulate bone formation, thus enabling the maintenance of BMD to limit bone loss and prevent the onset of osteoporosis (Pollock et al., 2010:421; Kruger et al., 2011:756; Andreoli et al., 2012:73; de Almeida Carvalho et al., 2014).

The results presented in Table 4.30 indicate that most of the participants (n = 21, 53%) include strength and conditioning exercises in their training regime twice per week (Table F.49 Appendix F). Table 4.30 indicates that there were no significant differences for the BMD, BF% and BMI respectively for those who implemented a strength and conditioning program and those who did not. The mean values for the BMD of the femoral neck, the hip total, the lumbar spine and the total body are slightly greater for those who do incorporate a strength and conditioning program and the Z-scores are slightly lower in those who implement a strength and conditioning program compared to those who do not. The BMI and BF% are slightly greater for those who do not implement a strength and conditioning-based program. None of the observed differences reflected in Table 4.30 were significant and the results should be interpreted with caution.

Research appears to recommend that long distance runners incorporate resistance exercises into their training regime to maintain BMD (Bemben et al., 2004:222; Bacelar et al., 2015:101). According to a study by Marques et al. (2011:529), participating in a resistance exercise training program for eight months was found to increase bone mass, especially in the hip region, due to the stimulation of bone formation. The implementation of a strength-based training regime stimulates the osteogenic activities of bone, which increases the BMD (Marques et al., 2011:529; Morseth et al., 2011:1230; Andreoli et al., 2012:74; Stunes et al., 2017:14). The present study could not find evidence in support of the recommendation by Bemben et al. (2004:222) and Bacelar et al. (2015:101).